tech_banner
Homing of liposomes to target cells | Request PDF
ArticleHoming of liposomes to target cellsAugust 1975Biochemical and Biophysical Research Communications 65(2):537-44SourcePubMedAuthors: Gregory GregoriadisUniversity of London E D NeerunjunE D NeerunjunThis person is not on ResearchGate, or hasn t claimed this research yet. Request full-text PDFTo read the full-text of this research, you can request a copy directly from the authors.Request full-textDownload citation Copy link Link copied Request full-text Download citation Copy link Link copiedTo read the full-text of this research, you can request a copy directly from the authors.Citations (147)References (13) Discover the world s research20+ million members135+ million publications700k+ research projectsJoin for freeNo full-text available To read the full-text of this research, you can request a copy directly from the authors.Request full-text PDFCitations (147)References (13)... [27][28][29]. One of the outcomes of this study was the recognition and the rise of a variety of 111 In labeled nanoparticles for SPECT imaging [30][31][32][33]. ...... appeared in the mid-1970s with the pioneering work of Gregoriadis. He demonstrated that 111 In-labelled liposomes carrying homing probes such as IgG and desialylated fetuin improved the selectivity of internalization in cell studies[33]. Further progress was made by V. Torchillin s group that decorated liposomes with covalently conjugated anticanine cardiac myosin antibodies. ...Historical Perspective on Nanoparticles in Imaging From 1895 to 2000ChapterJan 2015 Mikhail Y BerezinShortly after World War II in 1946, the U.S. Congress passed the Atomic Energy Act that transferred nuclear weapon development and nuclear power management to civilian, rather than military control. The majority of the efforts were directed toward the discovery of less expensive and more available sources of radioisotopes, the development of imaging instrumentation, and the medical assessment of the techniques. Optical imaging quickly advanced from a preclinical stage to use in clinical applications. Technically, microbubbles are vehicles that exceed the size of nanoparticles with a diameter in the 1–10 μm range. By the middle of the 1970s, liposomes have been the most advanced type of nanoparticles and presented an excellent scaffold for the incorporation of different types of molecules including multiple targeting moieties from small molecules to antibodies. New contrast agents became commercialized and rapidly adopted by clinics, which further accelerated the search for new contrast agents including nanoparticles.ViewShow abstract... Soon after Alec Bangham and his colleagues first described liposomes in the mid 1960s as closed vesicular structures able to envelop water soluble molecules, pharmacologists recognized their potential value in drug delivery (Bangham and Horne, 1964); the rationale was simple: use liposomes as a safe vehicle for delivering drugs more specifically to sites of disease while limiting exposure of normal tissues. (ii) Because of the minimization of allergic and other untoward reactions caused by drugs and proteins after their encapsulation in liposomes (Gregoriadis and Neerunjun, 1975). Cytotoxic anti-tumor agents were of particular interest as these in general have a narrow therapeutic window, i.e., doselimiting side effects limit their therapeutic utility. ...... Attempts to generate cell-targeting have focused primarily on the addition of monoclonal antibodies to the surface of the liposome. Liposomes tagged on their surface with IgG immunoglobulins directed against a variety of cell membrane proteins and desialylated fetuin which binds to the parenchymal cells of the liver can deliver bleomycin and mediate selective cellular uptake of the entrapped drug (Gregoriadis and Neerunjun, 1975). Apparently the hydrophobic IgG regions penetrate the lipid bilayers whereas the immunologically active portions are facing the exterior of the liposomes and are available for interaction with cells. ...The challenge of liposomes in gene therapyArticleJan 1998 Francis Joseph Martin Teni BoulikasSummary Recently, liposomes have gained a special interest as gene delivery systems: over 30 human clinical trials for gene delivery using cationic liposomes have been approved; all these delivery methods use intratumoral, subcutaneous and other local delivery but not systemic delivery due to the toxicity of cationic lipids. Stealth liposomes (coated with polyethyleneglyc ol to camouflage the liposome and evade detection by the immune system) have a remarkable longevity in body fluids, have negligible toxicity with respect to their lipid components, reduce the toxicity of the encapsulated drug, and can deliver efficiently their doxorubicin payload (DOXIL) or cis-platin to tumor lesions. The mechanism of stealth liposome accumulation in tumors involves their extravasation through gaps in the endothelium of tumor vessels. DOXIL can sustain a much higher concentration of Doxorubicin in tumor tissue compared to free drug administration at comparable doses. Liposomes tagged with folate-PEG or with antibodies can target specific tissues. We propose that stealth liposomes, could find future applications to systemically deliver plasmid DNA with therapeutic genes ( p53 , HSV- tk , angiostatin) to primary tumors and their metastases leading to complete cancer eradication. Abbreviations: AUC, area-under-the-plasma concentration vs time curve CHOL, cholesterol CL, cardiolipin DDAB, dimethyldioctadecylammonium bromide DOGS, dioctadecylamidoglycylspermine DOPE, dioleyl phosphatidylethanolamine DOSPA , (2,3-dioleyloxy-N-(20({2,5-bis((3- aminopropyl)amino)-1-oxypentyl}amino)ethyl)- N,N-dimethyl-2,3-bis(9-octadecenyloxy)-1- propanaminium trifluoroacetate DOTMA or lipofectin, N-(1-(2,3-dioleyloxy) propyl)-N, N, N trimethylammonium chlorideViewShow abstract... Liposomes that contain asialoglycoproteins (Gregoriadis and Neerunjun, 1975;Spanjer and Scherphof,1983) or are attached to LDL (Vidal et al.,1985) have been shown to be rapidly cleared by the liver, presumably mediated by hepatic recep tors for asialoglycoproteins and LDL. The supernatant was discarded. ...The applications of liposomes in immunoprophylaxis and immunotherapyThesisJan 1990Lloyd Seng Kee TanLiposomes have proven to be useful tools in numerous areas of biological research. The aims of this thesis are to further investigate their role and effectiveness in two different but well-established immunological applications, namely as adjuvants to bacterial and viral components and as antibody-mediated targeted carriers of entrapped drugs. Dehydration-rehydration vesicles (DRV) were found to be capable of entrapping relatively large reconstituted influenza virus envelopes (RIVE) with high efficiency and reproducibility. Balb/c mice inoculated with DRV containing RIVE exhibited primary and secondary IgG1 responses significantly higher as compared to mice inoculated with equal doses of unencapsulated RIVE. Similar responses were observed in the IgG2a , IgG2b and IgG3 subclasses. The adjuvanticity of liposomes on poorly immunogenic synthetic virus subunit peptides was demonstrated using DRV incorporating the peptides in their internal space and liposomes with covalently surface-linked peptides. It was found that liposome association boosted the primary and secondary IgG1 responses against the peptides as compared to controls in which free peptides were administered. Surface-linked peptide gave an initially more rapid rise in antibody levels as compared to entrapped peptide but with no immunological memory whereas one of the encapsulated peptides elicited a milder primary response but later exhibited a strong anamnestic response. The second part of the thesis relates to the behaviour of liposomes as targeted carriers of drugs. The influence of charge on the electrophoretic mobility of MLV in vitro and on the clearance from the circulation of SUV after intravenous administration was studied. It was found that positively-charged lipids (stearylamine and BisHOP) incorporated into DSPC SUV were cleared from the circulation in mice at the same rate as negatively-charged ones incorporating phosphatidic acid (PA), and in both groups, more rapidly than neutral SUV. However, stearylamine PC SUV were cleared more slowly than similarly positively-charged BisHOP PC SUV and negative PA PC SUV. This suggests that positively and negatively-charged SUV made by adding charged lipids to neutral phospholipids are cleared at the same rates if the charged lipid is confined in a rigid bilayer (eg. in DSPC SUV) or if the acyl chain of the charged lipid is saturated and long enough to prevent its removal from a more fluid bilayer (eg. in PC SUV). A study of the effect of pH on the electrophoretic mobility of charged MLV in vitro revealed that the net surface charge on liposomes is markedly influenced by changes in pH. These findings may have important implications for the clinical use of liposomes containing charged lipid, ligands or drugs and in states of acidosis or alkalosis. For use as targeting ligands, monoclonal antibodies that bound to 3 human hepatocellular carcinoma cell lines and snap-frozen sections of a patient s tumour were raised by the novel method of immunizing mice with PLC/PRF/5 membrane preparations. The monoclonals designated RF-HCC 1 and RF-HCC 2 were of IgG1 and IgM subclasses respectively. A simple method for the coating of liposomes with proteins was also developed. Several proteins (eg. BSA, pig gammaglobulins and tetanus toxoid) could be made to adhere rapidly and efficiently to both MLV and SUV after treatment with HC1 and NaNO2. The reaction is complete within four hours and almost all of the protein is retained on the liposomes after storage for 2 weeks at 4°C. CF-containing SUV coated with passively-adsorbed monoclonal antibody (RF-HCC1 and MOPC 21 IgG1) were used in in vitro studies for targeting to Mahlavu cells. Significantly greater amounts of the marker entrapped in antibody-coated SUV were associated with the target cells after incubation for one and a half hours at 4°C as compared to plain SUV. These results demonstrate that passively adsorbed antibodies represent a rapid, convenient and effective method of ligand-mediated targeting of SUV to cells in vitro.ViewShow abstract... In addition to these features, the ability of liposomes to destabilize their membranes for localised drug delivery (triggerable liposomes) is another highly crucial aspect for improving the efficacy of liposome-entrapped drugs and pharmaceuticals. Owing to this, liposomes have been exploited as carriers for drugs and pharmaceuticals since their inception [3][4][5]. The lipid bilayers can incorporate the lipophilic drugs while the hydrophilic drugs could be incorporated in the inner core [6,7]. ...Solid Lipid Nanoparticles: Promising Therapeutic Nanocarriers for Drug DeliveryArticleDec 2014Curr Drug Deliv Dipti Kakkar Shweta Dumoga Anil Kumar MishraDevelopment of colloidal delivery systems has opened new avenues/frontiers for improving drug delivery.Solid lipid nanoparticles have come up as the latest development in the arena of lipid based colloidal delivery systems after nanoemulsion and liposomes ever since their introduction in the early 1990s. In this review, the authors have made efforts to bring forth the essential and practically relevant aspects of SLNs. This review gives an overview of the preparation methods of solid lipid nanoparticles while mainly focussing on their biological applications including their projected applications in drug delivery. This review critically examines the influential factors governing the formation of SLNs and then discussing in detail the several techniques being utilized for their characterization. This review discusses the drug loading and drug release aspects of SLNs as these are useful biocompatible carriers of lipophilic and to a certain extent hydrophilic drugs. An updated list of drugs encapsulated into various lipids to prepare SLN formulations has been provided.Other relevant aspects pertaining to the clinical use of SLN formulations like their sterilization and storage stability have also been explained. A unique facet of this review is the discussion on the challenging issues of in vivo applications and recent progresses in overcoming these challenges which follows in the end.ViewShow abstract... Ligand modification gives a variety chance to the liposomal drug delivery systems to improve their therapeutic effects, including increase cell uptake, decrease side effects and dosage, reduce the period of treatment and induce specific targeting effects on intended site with high selectivity of drugs (Gao et al., 2013). Although liposomes are potential vehicles for site-specific drug delivery by which chemotherapeutic agent could be delivered directly to the intended site of tumor (Gregory Gregoriadis Neerunjun, 1975), finding of optimal liposome composition is still one of the challenges associated with liposomal drug delivery (Allen Cullis, 2004;Drummond, Meyer, Hong, Kirpotin, Papahadjopoulos, 1999). So far, different CA-4 liposomal formulations with a variety of ligands modification such as RGD peptide, SiaLe X (SiaLeX), octreotide, NGR and anti-E selectin (mAb) have been evaluated. ...Targeted-nanoliposomal combretastatin A4 (CA-4) as an efficient antivascular candidate in the metastatic cancer treatment: NIK et al.ArticleFull-text availableJan 2019J CELL PHYSIOL Maryam Ebrahimi Nik Amir Abbas Momtazi Parvin Zamani Bizhan Malaekeh-nikoueiA number of antiangiogenic drugs have been approved by the Food and Drug Administration which are used in cancer therapy, and variety of other agents in several stages of clinical development or in preclinical assessment. Among these, combretastatin A4 (CA‐4) is an under‐researched inhibitor of angiogenesis that shows potential activity in the treatment of advanced tumors with migration capacity. However, its clinical application has been limited due to poor water solubility, low bioavailability, rapid metabolism, and systemic elimination. During the last decade, numerous investigations have been done to overcome these problems by using different CA‐4 delivery systems or developing produgs of CA‐4 or its structural analogs. Nevertheless, these strategies could not be efficient out of the undesired side effects on normal tissues. Nanoliposomal CA‐4 not only benefits from the advantage of using liposomal drugs as opposed to free drugs but also can accumulate in the tumor site via specific targeting ligands, which leads to efficient targeting and enhancement of bioavailability. To the best of our knowledge, we consider an important attempt to understand different factors that might influence the CA‐4 loading and release pattern of liposomes and the consequent results in tumor therapy. In this review, we shed light on various studied liposomal CA‐4 formulations showing application thereof in cancer treatment.ViewShow abstract... Liposomes are ideal targeted delivery systems as they are relatively nontoxic and can carry hydrophilic or hydrophobic compounds either in the aqueous compartment or within the phospholipid bilayers, respectively. Liposomes may be targeted to a particular tissue by incorporating antibodies for a desired antigen into their outer membranes (Gregoriadis 1975;Drummond et al. 2010;. Researchers at the University of Cincinnati and University of Texas Health Science Center, Houston, have developed an echogenic targeted liposomal complex that can incorporate drugs and deliver them directly to cells Tiukinhoy-Laing et al. 2005;Klegerman et al. 2007). ...Ultrasound-enhanced drug delivery in a perfused ex vivo artery modelArticleJan 2010Kathryn E HitchcockAcoustically driven stable cavitation may improve treatments of diseases in which passive penetration of drug into the target tissue is poor. Examples include atherosclerosis, in which the endothelium can prevent penetration of therapeutics into the plaque, and ischemic stroke, in which pathologically low flow of blood impedes the delivery of intravenous drugs to the clot. Understanding the way in which ultrasound cavitation agents nucleate cavitation in flowing blood-mimicking solutions is an important step in optimizing ultrasound-enhanced drug delivery. The use of a perfused, living ex vivo artery model permitted study of this phenomenon while still providing information on arterial bioeffects. Cavitation-enhanced delivery of anti-ICAM-1-targeted echogenic liposomes into and beyond the ex vivo murine aortic endothelium was demonstrated using 1-MHz continuous wave ultrasound. Acoustic cavitation had no apparent effect on the health of the murine arterial tissue. A method of maximizing the energy of stable cavitation through the use of intermittent 120-kHz ultrasound with quiescent periods to allow contrast agent inflow was developed. Using this insonificaiton method, sonothrombolysis was studied in ex vivo porcine carotid arteries using a 120-kHz center frequency and 0.44 MPa peak-to-peak pressure amplitude. Clot mass loss was used as a metric of thrombolytic efficacy. Clots exposed to recombinant tissue plasminogen activator and the ultrasound contrast agent, DefinityRTM in flowing porcine plasma without ultrasound experienced 34% mass loss. When robust stable cavitation was induced via 120-kHz insonation, the mean clot mass loss rose to 83%, which constituted a significant improvement (n = 6, pViewShow abstract... The first attempts by Paul Erlich to create a magic bullet date back to the second half of the 1970s [4,5]: liposomes were conjugated with antibodies to specific receptors on the cell surface. It was expected that that such antibody-directed liposomes should selectively bind to target cells. ...From liposomes of the 1970s to 21st century nanobiotechnologyArticleFull-text availableJan 2008V. I. Shvets Alexander KaplunYu. M. Krasnopol’skiiV P ChekhoninThe review is devoted to actual problems of studying liposomes and other lipid nanoparticles that, being loaded with activesubstances, can be widely used in biomedical applications.ViewShow abstract... Amphiphilicity is the main advantages of liposomes in comparison to the other encapsulation systems [5]. These small size carriers also have suitable biocompatibility and low toxicity as well as commercial availability, easy preparation method (even in scaled up process), with high encapsulation efficiency [30][31][32][33][34]. Liposomes play a significant role in increasing the therapeutic index and reducing the side effects of drugs by sustained release of encapsulated core material [22]. ...Process Variables and Design of Experiments in Liposome and Nanoliposome ResearchArticleFull-text availableOct 2016MINI-REV MED CHEM Alaleh Zoghi Kianoush Khosravi Abdelwahab OmriLiposomes vesicles consisting of one or more phospholipid bilayers are microcarriers used in numerous scientific disciplines. During the last decade, nanostructured liposomes, or nanoliposomes, have been utilized in biomedical investigations due to their unique characteristics including nanoscale size, sustained release, biocompatibility, and biodegradability. The extensive literature covering the field of liposomology is an indication of increasing interests and applications in many areas, especially as carriers of active substances in nanomedicine, agriculture, food technology, and cosmetics. Nanoliposomes application as drug carriers resulted in more effective treatment of such diseases as cancers, atherosclerosis, infectious diseases and ocular disorders. In this communication we will introduce commonly used methods in liposomal preparation, identify the research and therapeutic field that utilize liposomes, and discuss the common process variables in liposome encapsulations. We will also review different screening methods and full and fractional factorial designs that impact independent variables in certain applications and the end-user response. We will review such key factors as encapsulation efficiency, loading capacity, particles’ biologics, structural and physicochemical properties, and lipid composition in an effort to provide a comprehensive guide for liposomologists in different field of interest.ViewShow abstract... Shortly after liposomes were first described, their promise as selective delivery agents was considered. To this end, Gregoriadis et al. associated molecular probes to drug-containing liposomes and found that probes (Immunoglobulin G s (IgGs) raised against different types of cells) could mediate selective cellular uptake [125]. In the early 1980s, Leserman et al. coupled monoclonal antibodies to liposome surfaces, successfully demonstrating cell-specific liposome interaction [126]. ...What Drives Innovation: The Canadian Touch on Liposomal TherapeuticsArticleFull-text availableMar 2019 Ada LeungCarolyn AmadorLin Chuan WangMarcel B. BallyLiposomes are considered one of the most successful drug delivery systems (DDS) given their established utility and success in the clinic. In the past 40–50 years, Canadian scientists have made ground-breaking discoveries, many of which were successfully translated to the clinic, leading to the formation of biotech companies, the creation of research tools, such as the Lipex Extruder and the NanoAssemblr™, as well as contributing significantly to the development of pharmaceutical products, such as Abelcet®, MyoCet®, Marqibo®, Vyxeos®, and Onpattro™, which are making positive impacts on patients’ health. This review highlights the Canadian contribution to the development of these and other important liposomal technologies that have touched patients. In this review, we try to address the question of what drives innovation: Is it the individual, the teams, the funding, and/or an entrepreneurial spirit that leads to success? From this perspective, it is possible to define how innovation will translate to meaningful commercial ventures and products with impact in the future. We begin with a brief history followed by descriptions of drug delivery technologies influenced by Canadian researchers. We will discuss recent advances in liposomal technologies, including the Metaplex technology from the author’s lab. The latter exemplifies how a nanotechnology platform can be designed based on multidisciplinary groups with expertise in coordination chemistry, nanomedicines, disease, and business to create new therapeutics that can effect better outcomes in patient populations. We conclude that the team is central to the effort; arguing if the team is entrepreneurial and well positioned, the funds needed will be found, but likely not solely in Canada.ViewShow abstract... These unique properties allowed A.D. Bangham to formulate the first preparation of liposomes with encapsulated materials in 1965 [34]. Since then, scientists have concentrated their efforts to take advantage of the characteristics of liposomes to understand the biophysical properties of membranes, study lipid interactions and to create efficient drug delivery systems35363738. The evolution of this concept led Yavlovich et al. [30] to design an innovative liposome formulation for potential use as an efficient drug release system in appropriate organs and at the appropriate times. ...Quantitative Analysis of Phospholipids Using Nanostructured Laser Desorption Ionization TargetsArticleFull-text availableFeb 2011 Simona ColantonioJohn T Simpson Robert J Fisher Robert BlumenthalSince its introduction as an ionization technique in mass spectrometry, matrix-assisted laser desorption ionization (MALDI) has been applied to a wide range of applications. Quantitative small molecule analysis by MALDI, however, is limited due to the presence of intense signals from the matrix coupled with non-homogeneous surfaces. The surface used in nano-structured laser desorption ionization (NALDI) eliminates the need for a matrix and the resulting interferences, and allows for quantitative analysis of small molecules. This study was designed to analyze and quantitate phospholipid components of liposomes. Here we have developed an assay to quantitate the DPPC and DC(8,9)PC in liposomes by NALDI following various treatments. To test our method we chose to analyze a liposome system composed of DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine) and DC(8,9)PC (1,2-bis(tricosa-10,12-diynoyl)-sn-glycero-3-phosphocholine), as DC(8,9)PC is known to undergo cross-linking upon treatment with UV (254 nm) and this reaction converts the monomer into a polymer. First, calibration curves for pure lipids (DPPC and DC(8,9)PC) were created using DMPC (1,2-dimyristoyl-sn-glycero-3-phosphocholine) as an internal standard. The calibration curve for both DPPC and DC(8,9)PC showed an R(2) of 0.992, obtained using the intensity ratio of analyte and internal standard. Next, DPPC:DC(8,9)PC liposomes were treated with UV radiation (254 nm). Following this treatment, lipids were extracted from the liposomes and analyzed. The analysis of the lipids before and after UV exposure confirmed a decrease in the signal of DC(8,9)PC of about 90%. In contrast, there was no reduction in DPPC signal.ViewShow abstract... The efficacy of liposomes as drug delivery systems would be increased dramatically if it were possible to deliver their contents selectively to particular cells or anatomical sites. Several types of liposomal formulations have been explored; such as those bearing carbohydrate determinants (lecithins), monoclonal antibodies, glycoproteins and antigens with a view of targeting the liposomes to selective tissues or anatomical sites [3,4]. However, most of these formulations have failed to show any remarkable therapeutic efficacy because of several reasons such as antigenicity of the ligands, inability of the drug to reach the appropriate cellular compartment in active form and the presence of the endothelial or other histological barrier between the liposomes and its cellular binding site. ...ENHANCED CELL KILLING BY METHOTREXATE ENCAPSULATED IN FOLATE TARGETED THERMOSENSITIVE LIPOSOMESArticleFull-text availableMay 2004 Mohamed H. GaberThe exploitation of folate receptor as Trojan horse to deliver folate-targeted liposomes bearing diverse cargo represents a novel therapeutic strategy to target folate receptor-expressing cells. In this paper, thermosensitive liposomes made of synthetic lipids (distearolphosphatidylcholine, DSPC and dipalmitoylphosphatidylcholine, DPPC) showing gel to liquid phase transition at 41º C, were used for encapsulation of methotrexate. The liposomes were prepared by thin film hydration method, the liposome binding constant K b for the drug was measured using a spectroscopic assay and was found to be 57.18 (mg/ml) –1. We have studied the liposome-mediated delivery of methotrexate to breast tumor cells in vitro, the cell sensitivity study was performed at normal physiological temperature (37º C) as well as hyperthermia increased temperature of 42º C. Moreover, a targeting moiety was used by modifying the liposome surface with folate using polyethyleneglycol (PEG) as a spacer. The ability of methotrexate to inhibit tumor cell growth is increased dramatically when encapsulated in targeted (folated) thermosensitive liposomes, but decreased when encapsulated in liposomes deficient folate. The index of cell Killing expressed as IC 50 was reduced dramatically from 7 µg/ml to 0.864 µg/ml upon using folate as a targeting moiety. Hyperthermia was not effective when used with non-specific targeted liposomes. However, the cytotoxicity of the drug increased dramatically upon heating folate targeted thermosensitive liposomes (the IC 50 was reduced to 0.34 µg /ml).ViewShow abstract... For this reason, substances that prolonged liposome blood circulation times which could evade rapid uptake by the MPS were discovered (Allen and Chonn 1987;Gabizon and Papahadjopoulos 1988), culminating in the development of PEG-coated, sterically stabilized liposomes (Papahadjopoulos et al. 1991;Senior et al. 1991;Lasic and Martin 1995). Many other approaches have been attempted to achieve targetable properties, including noncovalent association of cell specific antibodies with liposomes (Gregoriadis and Neerunjun 1975), coating of liposomes with heat aggregated immunoglobulins M (IgM) (Weissmann et al. 1975), and covalent attachment of poly and MAb to the liposomes, which selectively deliver the drug to the desired sites of action (Koning et al. 2002;Moribe and Maruyama 2002). Liposomal targeting through the integration of specific ligands and a mechanism of controlled drug release result in the accumulation of the drug at the site of action. ...Novel Drug Delivery Systems for Antifungal CompoundsChapterFull-text availableJun 2010 Qamar ZiaMohammad Farzuddin Mairaj Ahmed Ansari Mohammad OwaisDevelopment of new approaches for treatment of invasive fungal infections encompasses new delivery systems for approved and investigational compounds. Novel delivery systems consisting of cyclodextrins (CDs), cochleates, nanoparticles, and long-circulating (\"stealth”) liposomes modulate the pharmacokinetics of existing drugs, and may also be useful to enhance the delivery of antifungal agents to sites of infection. Among several promising new drug-delivery systems, liposomes represent an advanced technology for site-directed delivery of active molecules. Research on liposome technology has progressed from conventional vesicles (\"first-generation liposomes”) to \"second-generation liposomes,” in which long-circulating liposomes are obtained by modifying the surface of liposomes using several molecules, such as glycolipids, sialic acid, or synthetic polymer poly-(ethylene glycol) (PEG), resulting in prolonged reticulo-endothelial system uptake and serum half-life, thus increasing the therapeutic efficacy of drugs. At present, several formulations for amphotericin B are in clinical use for fungal infections in Europe and the United States. Nanoformulations have also been applied as drug delivery systems (DDSs), with great success. Finally, progress in the design of DDSs has led to the development of carriers targeted to specific tissues and cells. Efforts are now going on to improve their stability in the biological environment, to mediate the biodistribution of active compounds, and to improve drug loading, targeting, transport, release, and interaction with biological barriers. This chapter discusses the state of the art in the field of DDSs, used for control of systemic fungal infections.ViewShow abstract... 19,20 Since their inception, liposomes have been explored as carriers for delivering drugs and pharmaceuticals. [21][22][23][24][25][26] Currently, a number of liposome formulations are in clinical use to combat cancer and infectious diseases, while others await clinical trial outcomes. Historically, the important milestones that led to the research and development of clinically suitable liposome formulations can be summed up in two major technological achievements: (i) inclusion of PEGylated lipids in the liposomes bypass reticulo-endothelial system, resulting in significant drugs accumulation in the tumors 27,28 ; and (ii) the strategic development of a remote drug-loading process is based on the ammonium sulfate gradient method to achieve significant high quantities of drugs in the interior of the liposomes. ...PEG2000-DPSE-coated quercetin nanoparticles remarkably enhanced anticancer effects through induced programed cell death on C6 glioma cellsArticleNov 2013J Biomed Mater Res Gang WangJunjie WangJie Luo Jiang ShanqingIn this study, PEGylated nanoparticles quercetin drug delivery vehicles were investigated as carriers for anticancer drugs induced programed cell death (PCD). PEG2000-DPSE-coated quercetin nanoparticles were prepared and tumor cell killing efficacy was studied on glioma C6 cells and assayed for cell survival, apoptosis, or necrosis. The levels of ROS production and mitochondrial membrane potential (ΔΨm) were determined. Western blot assayed p53, p-p53, cytochrome C, and caspase proteins expression were also studied. Results indicate that PEG2000-DPSE-QUE-NPS showed dose-dependent cytotoxicity to C6 glioma cells and enhanced ROS accumulation induced upregulation of p53 protein, which was accompanied with an increase in cytochrome c and caspase-3 protein levels. These results support the hypothesis that quercetin nanoparticles-coated PEG2000-DPSE remarkably enhanced anticancer effect of induced programed cell death on C6 glioma cells. Overall, PEG2000-DPSE-coated quercetin nanoparticles showed promising potential as a drug carrier for cancer therapy. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2013.ViewShow abstractP5B-5 Echogenic Liposomes in High-Frequency Ultrasound ImagingConference PaperDec 2007Sheng-Chieh Lu Ja-an Annie HoChih-Kuang YehThe goal of this study is to estimate the acoustic properties of our self-made echogenic liposomes including effective working time, resonance frequency, nonlinear scattering and fragmentation using a 25-MHz high-frequency ultrasonic imaging system. Our self-made echogenic liposomes were also prepared based on the film hydration method and their average size was 1600 nm. We found that 0.3 mL buffer volume at 7 centigrade temperature mixing with dry 0.25 mg liposomes powder at 120 seconds vibration duration are the optimal conditions for ultrasound imaging. The effective working time of the echogenic liposomes was approximately 10 minutes. The resonance frequency range is from 7 to 11 MHz. As transmitting 10 MHz pulses, nonlinear scattering of echogenic liposomes can be observed and the inducing harmonic components intensities increase with increasing the acoustic pressure. Fragmentation phenomenon occurs in 10-cycle 2.25 MHz driven pulses with 0.15 MPa. Potential applications of the echogenic liposomes include the high-frequency nonlinear imaging in small animals and configured as targeted agents.ViewShow abstractPoloxamer sorption on liposomes: comparison with polystyrene latex and influence on solute effluxArticleDec 1988INT J PHARMACEUTM. Jamshaid Stephen FarrP. KearneyI.W. KellawayThe adsorption characteristics of several polyoxyethylene-polyoxypropylene (POE-POP) block copolymers (Synperonics) were studied on both polystyrene microspheres and small unilamellar vesicles (SUVs) composed of egg phosphatidylcholine (egg PC). Photon correlation spectroscopy (PCS) was used to monitor the increase in hydrodynamic radius following polymer sorption. Apparent adsorbed layer thickness (δ) of all POE-POP block copolymers was shown to be Langmurian. This δ increased non-linearly with the molecular weight of the polymer. Adsorption of Synperonic F108 occurred rapidly onto latex particles with no subsequent change of hydrodynamic radius on storage. For SUVs, δ was significantly less (P 0.05) than that measured for the same polymer with polystyrene microspheres, which may indicate a degree of bilayer penetration by the polymers. The efflux rate of entrapped 6-carboxyfluorescein (6-CF) was considerably lower for SUVs prepared from egg PC and cholesterol (1 : 1 molar ratio) than for those prepared from egg PC alone when suspended in Synperonic F108. Retention of 6-CF was higher for multilamellar vesicles (MLVs) than for SUVs when incubated in the same polymer solution.ViewShow abstractTargeting of antiviral drugs to the liver using glycoprotein carriersArticleApr 1994ADV DRUG DELIVER REVL FiumeC BusiGiuseppina Di StefanoA MattioliIn order to improve the efficacy and to reduce the side-effects of antiviral drugs in the treatment of chronic hepatitis B, a lysosomotropic approach through covalent linkage of the drugs to appropriate glycoproteins was adopted. Antiviral nucleoside analogs were coupled to asialofetuin and to lactosaminated albumin (L-SA) (two galactosyl-terminating glycoproteins). The conjugates were selectively taken up by liver cells where they released the drugs in a pharmacologically active form. L-SA conjugates showed the advantage of being non-immunogenic when prepared with homologous albumin and injected intravenously. The majority of the experiments reported in this article were performed employing a conjugate of L-SA with ara-AMP, a drug active against hepatitis B virus (HBV). The results of animal studies warranted a 7-day administration of L-HSA-ara-AMP to patients with chronic hepatitis B. Conjugated ara-AMP was shown to inhibit HBV growth at a dose 3–6 times lower than that of the free drug.ViewShow abstractMagnetic Microspheres: Synthesis of a Novel Parenteral Drug CarrierArticleFeb 1979J Pharmaceut SciKenneth J. WidderGeorge FlouretAndrew E. SenyeiThe synthesis and characterization of a novel parenteral drug carrier capable of area specific localization by magnetic means are described. The carrier consists of human serum albumin microspheres, average of 1 μm in diameter, in which a magnetizable material (magnetite) and a prototype drug (doxorubicin) are entrapped. Stabilization of the microsphere matrix by formaldehyde, 2,3-butanedione, and heat conferred equal stability to the matrix but differentially affected the in vitro drug release rate. Released doxorubicin was chemically identical to the starting material.ViewShow abstractFolate-mediated tumor cell targeting of liposome-entrapped doxorubicin in vitroArticleMar 1995Biochim Biophys Acta Robert J Lee Philip LowReceptors for the vitamin folic acid are frequently overexpressed on epithelial cancer cells. To examine whether this overexpression might be exploited to specifically deliver liposome-encapsulated drug molecules in vitro, folate-targeted liposomes were prepared by incorporating 0.1 mol% of a folate-polyethyleneglycol-distearoylphosphatidylethanolamine (folate-PEG-DSPE) construct into the lipid bilayer, and were loaded with doxorubicin (DOX), an anti-cancer drug. Uptake of folate-PEG-liposomal DOX by KB cells was 45-fold higher than that of non-targeted liposomal DOX, and 1.6-times higher than that of free DOX, while the cytotoxicity was 86 and 2.7-times higher, respectively. Folate-targeting is fully compatible with PEG-coating of the liposomes, since incorporation of 4 mol% PEG2000-DSPE does not reduce the uptake or cytotoxicity of folate-PEG-liposomal DOX. Uptake of folate-PEG-liposomes was inhibited by 1 mM free folic acid but was unaffected by physiological concentrations of folate. In HeLa/W138 co-cultures, folate-PEG-liposomes encapsulating calcein, a fluorescent dye, were found to be almost exclusively internalized by the HeLa cells which overexpress the folate receptors. We suggest that folate targeting constitutes a possible mechanism for improving the specificity of PEG-coated liposomes for cancer cells.ViewShow abstractLiposome technology for cardiovascular disease treatment and diagnosisArticleFeb 2012Kristen Bowey Jean-François Tanguay MdMaryam TabrizianIntroduction: Over the past several decades, liposomes have been used in a variety of applications, from delivery vehicles to cell membrane models. In terms of pharmaceutical use, they can offer control over the release of active agents encapsulated into their lipid bilayer or aqueous core, while providing protection from degradation in the body. In addition, liposomes are versatile carriers, because targeting moieties can be conjugated on the surface to enhance delivery efficiency. It is for these reasons that liposomes have been applied as carriers for a multitude of drugs and genetic material, and as contrast agents, aimed to treat and diagnose cardiovascular diseases.Areas covered: This review details advancements in liposome technology used in the field of cardiovascular medicine. In particular, the application of liposomes to cardiovascular disease treatment and diagnosis, with a focus on delivering drugs, genetic material and improving cardiovascular imaging, will be explored. Advances in targeting liposomes to the vasculature will also be detailed.Expert opinion: Liposomes may provide the means to deliver drugs and other pharmaceutical agents for cardiovascular applications; however, there is still a vast amount of research and clinical trials that must be performed before a formulation is brought to market. Advancements in targeting abilities within the body, as well as the introduction of theranostic liposomes, capable of both delivering treating and imaging cardiac diseases, may be expected in the future of this burgeoning field.ViewShow abstractThe interaction of liposomes with cells: The relation of cell specific toxicity to lipid compositionArticleDec 1980Eur J CancDerek LaytonG A Luckenbach Reinhard AndreesenP G MunderLiposomes, which have been proposed as agent carriers, can themselves produce a wide variety of effects on the viability of co-incubated cells.In this study we show that the lipid composition of empty liposomes produced varied effects on the viability, as measured by [3H]-thymidine incorporation, of leukemic cells and fibroblasts. Certain liposomal compositions, particularly those involving stearylamine, were highly toxic to both cell types.It is evident from this investigation that caution must be exercised in the choice of lipid composition if the effect of the liposomes is not to conceal that of the drug, or carried agent, either on the target cells in terms of therapeutic effect, or on normal cells in terms of toxicity.Normal lysophosphatides, having an acyl bond in sn-1, can be metabolised by both normal and leukemic cells; however the replacement of the acyl by an alkyl bond in a lysophosphatide requires an O-alkyl cleavage enzyme to be metabolised. Such an enzyme is present in a multifunctional oxygenase in normal cells but appears to be absent or inoperative in certain tumor cells.Coincubation of alkyl lysophosphatide containing liposomes is shown to produce selective destruction of L1210 leukemic cells; in addition the liposomal form of such analogs is suggested as being more effective against leukemic cells and less toxic to normal cells than when used in the free form.ViewShow abstractA newly developed immunoliposome/Man egg phosphatidylcholine liposome coated with pullulan bearing both a cholesterol moiety and an IgM fragmentArticleMay 1987Biochim Biophys ActaJunzo SunamotoToshinori SatoMasaki HirotaKohei HaraAn improved methodology for providing a more stable and targetable drug carrier has been developed. This method involves the synthesis of a newly designed immunoliposome by coating the outermost surface of large oligolamellar vesicles of egg phosphatidylcholine with the polysaccharide pullulan, modified to carry both cholesterol, as the hydrophobic anchor, and the monoclonal antibody fragment (anti-sialosyl LewisX, IgMs) as the sensory device. Compared with the binding of pullulan-coated liposomes, that of this immunoliposome to specific cells in vitro was significantly increased by factors of 447 to PC-9 and 295 to KATO-III, but only by a factor of 148 to the less specific cell, 3LL. This strong and specific binding of the immunoliposome to the cell surface of PC-9 was also confirmed by a fluorescence-microscopic investigation using the immunoliposome, which bore the hydrophobic fluorescent probe, terbium trisacetylacetonate, in the liposomal membrane.ViewShow abstractLipid-Based Nanocarriers for CNS-Targeted Drug DeliveryArticleFull-text availableApr 2012Maria-Rita MicheliRodolfo Bova Alessandro Magini Carla EmilianiNanotechnology exerts an increasing impact on the development of more effective tools for the diagnosis and treatment of human diseases. This applies in particular to central nervous system (CNS) disorders. Development of therapeutics for CNS is, in fact, one of the most challenging areas in drug development, mainly due to the presence of the blood-brain barrier (BBB) which separates the blood from the cerebral parenchyma thus limiting the brain uptake of the vast majority of neurotherapeutic agents. Among the several strategies which have been developed over the last years in order to overcome this problem, nanotechnology-based approaches have gained increasing attention as the most promising strategies for CNS targeted drug delivery. Nanocarriers offer several advantages such as the possibility to maintain drug levels in a therapeutically desirable range, as well as the increase of half-lives, solubility, stability and permeability of drugs. Furthermore, the system can be designed in such a way as to release the drug in a controlled way or in a triggered way. This review focuses on lipid-based nanocarriers and more specifically on liposomes, lipid-core micelles, and lipid nanocapsules, and provides an update on their composition and use, including recent patents in the field.ViewShow abstractBiopolymer albumin for diagnosis and in drug deliveryArticleMar 2003Drug Dev Res Gayathri Vishwanath PatilThis article reviews the developmental stages and strategies used to assess the biomedical utility of biopolymer albumin from the 1970s to early 2002. The basic method and mechanism(s) of preparation of albumin microspheres and subsequent modifications made to overcome the drawbacks of earlier approaches and the need for further developments are discussed, as are the processing parameters and the level of various ingredients affecting the physicochemical properties of the albumin microspheres. Different equations proposed by various investigators to modulate in vitro release kinetics are reviewed. The microscopic structural and surface properties, the chemical modification of the biopolymer (e.g., cationization, tagging with amino acids and sugar moieties) for tissue specificity or to influence the release profile and biodegradation are discussed. An array of potential diagnostic applications and the use of albumin microspheres as a drug delivery system are reviewed. Drug Dev. Res. 58:219–247, 2003.© 2003 Wiley-Liss, Inc.ViewShow abstractKinetic and Thermodynamic Approaches to the Drug Targeting PhenomenaArticleJul 2011Curr Drug Discov Tech Igor Meerovich Alexander Koshkaryev Vladimir P TorchilinThe effectiveness of many promising drug candidates (e.g. anticancer agents) awaits the development of drug forms capable of delivery of their drug load specifically to particular sites of an organism or a cell. To make universal and efficient drug carriers, administered drug-loaded vehicles should be able to reach the pathologic zone, recognize and bind their targets at a therapeutic concentration before clearance from the organism. Numerous methods have been developed to couple drug vehicles with active targeting substances - including monoclonal antibodies and substrates or ligands for pathologic cell receptors. Other approaches have included the use of such factors as decreased pH and elevated activity of enzymes in tumor tissues and the hypoxic environment inside the tumor core. This review makes an attempt to analyze the main factors that influence targeting on the kinetic or thermodynamic level that may provide the basis for a strategy to develop and improve drug delivery systems.ViewShow abstractInteraction of antibody-bearing small unilamellar liposomes with antigen-coated cells. The effect of antibody and antigen concentration on the liposomal and cell surface respectivelyArticleFull-text availableNov 1981BIOCHEM J Gregory GregoriadisAnne MeehanHuman blood lymphocytes were coated with increasing amounts of human kappa chain (2-85mug/10(7) cells) through the linking reagent CrCl(3). These cells were then exposed to small unilamellar liposomes composed of egg phosphatidylcholine, cholesterol and phosphatidic acid (molar proportions 7:7:1) containing carboxyfluorescein and/or (111)In-labelled bleomycin and bearing (131)I-labelled affinity chromatography-purified or non-purified anti-(kappa-chain) immunoglobulin G (IgG) [see the preceding paper, Gregoriadis, Meehan Mah (1981) Biochem. J.200, 203-210]. In some experiments liposomes contained [(14)C]phosphatidylcholine. (1) Lymphocytes (10(7)) coated with 2-85mug of kappa chain and exposed to liposomes devoid of IgG or bearing non-purified anti-(kappa chain) IgG bound only a small proportion of the liposomal markers. Even with liposomes bearing the purified anti-(kappa chain) IgG, uptake of the labels improved only slightly for cells coated with up to 10mug of kappa chain. However, with higher concentrations of the antigen on the cell surface, binding was improved considerably to reach values of 31% ((111)In-labelled bleomycin) and 43% ((131)I-labelled IgG) of added liposomes for cells coated with 85mug of kappa chain. (2) Lymphocytes coated with kappa chain were exposed to liposomes bearing increasing amounts (0-180mug/0.9mg of egg phosphatidylcholine) of purified anti-(kappa chain) IgG. It was found that under the present conditions, binding of all three markers ((111)In-labelled bleomycin, (131)I-labelled IgG and [(14)C]phosphatidylcholine) was directly proportional to the concentration of IgG on the liposomal surface. However, uptake values remained unchanged above 90mug of IgG. (3) Antibody-mediated uptake of liposomes by cells coated with the corresponding antigen without loss of their metabolic activities may provide a method of efficient targeting.ViewShow abstractStructural stability and binding properties of soluble and membrane-anchored recombinant antibodiesArticleJan 2001Kaija AlfthanAntibody engineering and advances in microbial expression systems have enabled production of small, active antibody fragments. However, the functional expression yields of these recombinant antibodies vary widely. The results described in this thesis elucidate factors influencing the expression of stable and active antibody fragments in bacteria. The model antibody used throughout this study was a mouse monoclonal antibody binding to 2-phenyloxazolone (Ox). It was shown that the first constant domain of the heavy chain (CH1) has a remarkable effect on secretion of functional and stable Fab fragments. Comparison of the production of the Ox IgG1 and Ox IgG3 subclass Fab fragments in bacteria demonstrated the superiority of the Ox IgG1 Fab compared to the Ox IgG3 Fab. In addition to its effect on secretion, the CH1 domain contributes to the thermal stability of the antibody fragments. To study the effect of a linker peptide on both proteolytic stability and binding activity of single-c hain antibodies, six different Ox scFv derivatives and an Ox Fy fragment with no joining peptide between the variable domains were constructed. It was shown that joining of the variable domains with a linker peptide improved hapten binding properties compared to the Ox Fv fragment, but may expose the fragment to proteolytic degradation. Truncation of the linker peptide to less than 12 amino acids induced formation of dimers or multimers. The binding affinities determined for the monomeric Ox scFv and Ox IgG1 Fab fragments using the BIAcore biosensor and fluorescence quenching methods were close to each other and comparable to that of the parental monoclonal antibody. In addition to studies with soluble antibody fragments, this work was extended to cover characterization of antibody fragments displayed on liposomes and on the surface of baculovirus. Immunoliposomes have potential applications both in therapy and in immunodiagnostics. In this work liposomes displaying antibodies were generated by incorporation of purified lipid-tagged Ox scFvs expressed in E. coli into phospholipid liposomes. It was demonstrated that the biosynthetically lipid-tagged Ox scFv molecules can be immobilized in a functional, stable and oriented manner onto liposomal membranes, resulting in immunoliposomes showing specific hapten binding. BIAcore analysis of the immunoliposomes revealed very slow dissociation from the Ox surface, which is in good agreement with the predicted multivalent nature of the immunoliposomes. The baculoviral display approach holds a promise as a candidate for a eukaryotic display system. In this work single-chain antibodies were used as a model to investigate functional expression of foreign proteins on the surface of baculovirus. Viral vectors displaying cell targeting moieties such as single-chain antibodies have aroused interest as gene transfer vehicles. Two Ox scFv derivatives and a human scFv specific for carcinoembryonic antigen (CEA) were fused to the major envelope protein (gp64) of the Autographa califo rnica nuclear polyhedrosis virus (AcNPV). It was shown that the two single-chain antibodies which contained a (GGGGS)3 linker peptide were incorporated into the budded virus particles and expressed as functional hapten/antigen binding fragments on the viral surface. In the case of the third scFv containing a natural linker peptide derived from a fungal cellulase, less efficient incorporation into the virus particles was observed.ViewShow abstract Smart Liposomal Nanocontainers in Biology and MedicineArticleFull-text availableJul 2010Biochemistry Yury S. TarahovskyThe perspectives of using liposomes for delivery of drugs to desired parts of the human body have been intensively investigated for more than 30 years. During this time many inventions have been suggested and different kinds of liposomal devices developed, and a number of them have reached the stages of preclinical or clinical trials. The latest techniques can be used to develop biocompatible nano-sized liposomal containers having some abilities of artificial intellect, such as the presence of sensory and responsive units. However, only a few have been clinically approved. Further improvements in this area depend on our knowledge of the interactions of drugs with the lipid bilayer of liposomes. Further studies on liposomal transport through the human body, their targeting of cells requiring therapeutic treatment, and finally, the development of techniques for controlled drug delivery to desired acceptors on cell surfaces or in cytoplasm are still required.ViewShow abstractNanoimaging and neurological surgeryArticleNov 2010Ion Dan GrosuMadalina Alexandra Toms Steven A TomsOver 32 million surgical procedures are performed in the United States each year. Increasingly, image guidance is used in order to aid in the surgical localization of pathology, minimization of incisions, and improvement of surgical intervention outcomes. A variety of imaging modalities using different portions of the electromagnetic spectrum are used in neurological surgery. These include wavelengths used in ultrasonography, optical, infrared, ionizing radiation, and magnetic resonance. The use of currently available image-guidance tools for neurological surgery is reviewed. Advances in nanoparticulates and their integration into the neurosurgical operating room environment are discussed. WIREs Nanomed Nanobiotechnol 2010 2 601–617For further resources related to this article, please visit the WIREs websiteThe authors have nothing to disclose.ViewShow abstractThermochemotherapy: Synergism Between Hyperthermia and Liposomal Bleomycin in Mice Bearing Melanoma B16F1ArticleFull-text availableJan 2000J PHARM PHARMACOL Sandip Tiwari Nayanabhirama Udupa Satish Bola Sadashiva Rao Puja DeviThis study was aimed at enhancing the antitumour efficacy of bleomycin by encapsulating it in temperature-sensitive liposomes and using it in combination with localized hyperthermia of tumours for targeted delivery.Large unilammelar vesicles (LUV) made of synthetic lipids (disteroyl phosphatidylcholine and dipalmitoyl phosphatidylcholine) showing gel-to-liquid phase transition at 41°C, were used to encapsulate bleomycin. Comparison of LUV when incubated in saline at various temperatures revealed that maximum drug release (80%) occurred at 42°C compared with less than 5% release at 37°C. Better stability during storage was also observed with thermosensitive bleomycin liposomes. When administered intravenously to C57BL/6J mice bearing melanoma B16F1 tumour at 10 mg kg−1 dose, liposomal bleomycin in combination with hyperthermia (43°C, 30 min or 1 h) exhibited improved anticancer activity as evident by the enhanced volume doubling time and growth delay compared with animals treated with an equivalent dose of free bleomycin with or without hyperthermia.The results suggest that hyperthermia in combination with bleomycin encapsulated in temperature sensitive liposomes may be a useful targeted drug delivery system for more effective management of melanoma B16F1.ViewShow abstractDrug-containing lipid vesicles render drug-resistant tumour cells sensitive to actinomycin DArticleJun 1976George PosteDemetrios PapahadjopoulosDEVELOPMENT of cellular resistance to actinomycin D (AD) has been reported in tumour cell populations in vivo1,2 and in vitro3–6. Such cells have a lower capacity than normal to incorporate AD3,6–8, prompting suggestions that the AD-resistant phenotype is determined by changes in plasma membrane function that reduce cellular permeability to this drug. Support for this proposed mechanism of drug resistance has been provided by experiments showing that treatment of AD-resistant cells with membrane-active detergents, to increase plasma membrane permeability, enhances AD uptake by resistant cells and reduces the concentration of AD required to inhibit cell growth8,9. This approach, while instructive, has the disadvantage that the detergent causes significant alteration in cell viability and also impairs cell growth8. We now report a new method for enhancing drug uptake by permeability restriction, drug-resistant cells which uses lipid vesicles as carrier agents to introduce AD directly into cells. As reported elsewhere10,11, negatively-charged lipid vesicles composed of lipids or lipid mixtures that are \"fluid” at 37 °C are incorporated into cultured cells by fusion with the cellular plasma membrane. Entrapment of drugs inside such vesicles and subsequent fusion of the vesicles with cells offers a potential method for bypassing the plasma membrane transport barrier to introduce drugs directly into the intracellular compartment. Since vesicles are not cytotoxic10–12, their use as drug carriers allows direct evaluation of the cellular response to the introduced drug, free from the complications8,9,13 associated with the use of detergents. The results presented here indicate that uptake of vesicles containing AD by AD-resistant cells produces inhibition of cellular RNA synthesis and cell growth at AD concentrations that have no effect on cells when added as free drug to the culture medium.ViewShow abstractLiposomes as lysosomotropic carriersArticleDec 2006Ann New York Acad SciChristian de DuveAndré TrouetDanielle Deprez‐de CampeneereRoger BaurainViewHepatocyte targeting using pegylated asialofetuin-conjugated liposomesArticleDec 2013J Drug Target Pascal Detampel Dominik Witzigmann Stephan Krahenbuhl Jörg HuwylerAbstract Background and purpose: The hepatocyte asialoglycoprotein receptor mediates uptake of desiaylated glycoproteins by receptor-mediated endocytosis. This work explores a hepatocyte-specific targeting strategy using asialofetuin (AF) covalently coupled to pegylated liposomes. Methods: AF was conjugated to the distal end of polyethylene glycol-functionalized phospholipids. Chemical modification of AF did not interfere with its receptor interaction. AF-liposomes had a size of less than 130 nm, were judged to be monodisperse and were labelled with fluorescent organic dyes or loaded with quantum dots. Results: In vitro, binding and cellular uptake of fluorescent AF-liposomes by HepG2 hepatocellular carcinoma cells were reduced at low temperature and could be competitively inhibited by an excess of unbound AF. Hepatocyte-specific targeting and internalization of AF-liposomes in vivo was confirmed in the rat and could be competitively inhibited by co-injection of unbound AF. In contrast, non-pegylated liposomes accumulated in cells of the reticuloendothelial system such as hepatic Kupffer cells and spleen after intravenous administration. Conclusion: We conclude that the use of AF-conjugated, pegylated liposomes is a promising strategy to avoid the reticuloendothelial system and specifically target hepatocytes via the asialoglycoprotein receptor in vitro as well as in vivo.ViewShow abstractEnhancement of antitumor effect on urological cancer in vitro and in vivo by drugs entrapped in liposomeArticleJan 1983Jpn J UrolMasaaki TachibanaNobuhiro DeguchiMasamichi HagiwaraHiroshi TazakiLiposome is a bilayered phospholipid vesicles, and was originally developed as a model for biomem-branes. Liposome has attracted attention in recent years as a potential carrier of anticancer drugs thereby enhancing the therapeutic effect. This study was designed to clarify the following problems associated with clinical application of liposome in future.1) The influence of liposome-entrapped anticancer drugs on cytotoxic activity in in vitro system.2) The effect of liposome-entrapped anticancer drugs in the host tissues.3) The in vivo therapeutic efficacy of liposome-entrapped bleomycin in the treatment of testicular tumor transplanted in nude mice.For cytotoxicity test, KU-2 cells, dervived from human renal cell carcinoma were used. Effect of free and liposome-entrapped bleomycin on the growth of KU-2 cells was determined. Enhanced effect was noted in the latter group. Also effect of free and liposome-entrapped bleomycin on the cell cycle traverse of KU-2 cells was determined by means of flow microfluorometry. Obvious effects of G2-block was noted in liposome-entrapped bleomycin.Therapeutic effect of free and liposome-entrapped bleomycin on the testicular tumor bearing nude mice (KUNU-1) was examined. Antitumor effects of bleomycin was enhanced by entrapment of bleomycin into liposome, mean growth rates of the tumor by administration of free and liposome-entrapped bleomycin at day 5 were 91.1±8% and 76.1±14%, respectively.Bleomycin, either free or liposome-entrapped, was injected into the peritoneal cavity of KUNU-1 mice in a dose of 5mg. When liposome-entrapped bleomycin was given, increase in the concentration of bleomycin was sixfold in the spleen; threefold in the liver; twofold in the kidney and one and half fold in the lung.These results indicate that liposome entrapment modified the pharmacokinetics and enhanced the anticancer activity of the drug mediated by slow delivery rather than providing selective cytotoxic effect of the drug to tumors.ViewShow abstractTargeting of drugs with liposomesChapterJan 1983 Gregory GregoriadisAt least two options are open to us in pursuing optimal drug action (Gregoriadis, 1981a). In the first, creation of specialised molecules, a therapeutically profitable target-drug relationship is usually far from ideal and undesirable side effects are almost always present. In the second, drug molecules that are not necessarily target specific are transported by a carrier to the area of action and subsequently allowed to perform their task. Transport by the carrier should be effected in isolation from the biological space existing between the site of application and the site of action as this would be useful in cases where drugs are either prone to premature excretion and inactivation or detrimental to the non-target space in the host. The carrier itself should be non-toxic, biodegradable and of the appropriate shape and size so as to enable accommodation of a wide variety of therapeutic agents. It should preferably ignore or be ignored by irrelevant (normal) areas and have a pronounced affinity for, and access to the target site within which there should be a mechanism for the release of agents from the carrier. The latter, having accomplished its function, should then be disposed of.ViewShow abstractRecent advances in oral drug delivery systemsChapterDec 2013 Tolulope Omolola Ajala Olufunke D. Akin‐Ajani Oluwatoyin OdekuViewAntibody-Mediated Targeting of LiposomesChapterJan 1982John N WeinsteinLee Leserman Pierre Alfred Henkart Robert BlumenthalWe have studied a number of permutations on the use of antibody and antigen for targeting liposomes in vitro. Our first strategy was to make liposomes with lipid bearing the dinitrophenyl (DNP) hapten. These liposomes bound specifically to cells in three experimental configurations: (i) with TNP-modified human peripheral blood lymphocytes as targets and sheep IgG anti-TNP as cross-linking agent; (ii) with murine myeloma MOPC 315 cells (which bear an IgA with high affinity for nitrophenyl haptens) as target, using endogeneous surface immunoglobulin on the cells as a point of attachment; (iii) with Fc-receptor bearing cells as targets and rabbit anti-TNP as an opsonizing agent. We monitored the interactions by encapsulating carboxyfluorescein and/or methotrexate in the liposomes, and in some experiments by incorporating 14C-dipalmitoyl phosphatidylcholine or a fluorescent marker in the lipid. In each study large numbers of liposomes could be bound specifically to the target cells, but they were internalized in significant numbers only in (iii) when cells capable of Fc-mediated endocytosis were used. The most striking internalization was found with the mouse macrophage line P388D1. Encapsulated methotrexate had a several-fold greater effect on the metabolism of P388D1 (as assayed by 3H-deoxyuridine uptake) than did an equivalent amount of methotrexate free in solution. This finding indicated that an appropriately chosen drug can escape the phagosomal system to exert its effect in the cytoplasm.ViewShow abstractDevelopment of Liposomes as an Efficient Carrier System: New Methodology for Cell Targeting and Intracellular Delivery of Drugs and DNAChapterJan 1982F. MartinRobert M. StraubingerDemetrios PapahadjopoulosTimothy D. HeathLiposomes are a valuable carrier system for enhancing the pharmacological activity of drugs and the functional incorporation of macromolecules into cells. During the last few years, we have concentrated on developing new liposome methodology designed to optimize their properties as a carrier system. We will describe some of these procedures related to the following specific topics: (1) efficiency of encapsulation: the reverse phase evaporation method produces large unilamellar vesicles (0.2–0.4 μdiameter) encapsulating approximately 50% of the initial aqueous phase. This procedure is particularly valuable for the encapsulation of large macromolecules such as RNA and DNA which can be entrapped with very high efficiency and no appreciable degradation. (2) control of vesicle size: extrusion of liposomes through nucleopore membranes produces vesicles which conform to the membrane pore diameter without loss of material. This allows the preparation of reasonably homogeneous populations of unilamellar vesicles in the range of 0.1–0.2 μ in diameter. (3) control of liposome permeability: minimizing permeability by increasing the cholesterol content increases dramatically in vivo anti-tumour effects. This has been tested with Ara-C containing vesicles against L1210 leukemia in mice. (4) intracellular delivery of macromolecules: the infectivity of liposome-encapsulated SV40 DNA is enhanced up to 1000-fold over free DNA and is dependent on the vesicle lipid compositions and the incubation conditions. The highest infectivity is achieved with vesicles composed of phosphatidylserine and cholesterol (1:1 mole ratio) in the presence of chloroquine, and in conjunction with a short post-incubation treatment with high concentrations of glycerol. Under these conditions, the infectivity of SV40 DNA (3 x 105 pfu/ g DNA) is comparable or greater than can be obtained using the Ca3(PO4)2techniques for DNA delivery. (5) targeting to specific cells: the covalent attachment of cell specific F(ab’)2 and Fab’ fragments of IgG to the liposome surface induces nearly quantitative uptake of liposomes by target cells. These new procedures increase by 100-fold the uptake of liposomes and their contents by the target cells. Current studies involve monoclonal antibodies against a variety of human and murine antigenic determinants.ViewShow abstractCo-Encapsulating the Fusogenic Peptide INF7 and Molecular Imaging Probes in Liposomes Increases Intracellular Signal and Probe RetentionArticleFull-text availableMar 2015PLOS ONE Scott R BurksEric A. Legenzov Erik Martin Joseph KaoLiposomes are promising vehicles to deliver diagnostic and therapeutic agents to cells in vivo. After uptake into cells by endocytosis, liposomes are degraded in the endolysosomal system. Consequently, the encapsulated cargo molecules frequently remain sequestered in endosomal compartments; this limits their usefulness in many applications (e.g. gene delivery). To overcome this, various fusogenic peptides have been developed to facilitate delivery of liposomally-encapsulated molecules into the cytosol. One such peptide is the pH-sensitive influenza-derived peptide INF7. Liposomal delivery of imaging agents is an attractive approach for enabling cell imaging and cell tracking in vivo, but can be hampered by inadequate intracellular accumulation and retention of probes caused by exocytosis (and possible degradation) of endosome-entrapped probes. Such signal loss could be minimized by facilitating escape of probe molecules from endolysosomal compartments into the cytosol. We investigated the ability of co-encapsulated INF7 to release liposomally-delivered rhodamine fluorophores into the cytosol after endosomal acidification/maturation. We co-encapsulated INF7 and fluorescent rhodamine derivatives having vastly different transport properties to show that after endocytosis by CV1 cells, the INF7 peptide is activated by acidic endosomal pH and facilitates efficient release of the fluorescent tracers into the cytosol. Furthermore, we show that INF7-facilitated escape from endosomes markedly enhanced retention of tracers that cannot be actively extruded from the cytosol. Minimizing loss of intracellular probes improves cellular imaging by increasing the signal-to-noise ratio of images and lengthening the time window that imaging can be performed. In particular, this will enhance in vivo electron paramagnetic resonance imaging, an emergent magnetic resonance imaging modality requires exogenous paramagnetic imaging agents and is highly promising for cellular and molecular imaging.ViewShow abstractQuantitative In Vivo Assessment of Tumour Vasculature- Targeted LiposomesArticleFull-text available Michael DunneViewProceedings Articles: \"… Twinkling guide stars to throngs of acolytes desirous of your membranous semi-barriers. Precursors of bion, potential drug carriers …”ArticleJan 1995J LIPOSOME RES Gregory GregoriadisLiposomes have played a pivotal role in our efforts to improve drug action in therapeutics. Thanks to the input of an ever increasing number of individuals with diverse interests and from a variety of backgrounds, the system has evolved laterally from a powerful tool for the study of cell membrane biophysics to life saving constructs. Its odyssey, from initial enthusiasm, through milestones of ideas and concepts, alternating troughs of optimism and pessimism and predictable bouts of assaults or applause, continues, but Ithaka is no longer ellusive. My contribution to \"Nostalgia” will, as the title(l) above suggests, deal with early events in the voyage.ViewShow abstractLiposomes for drug delivery: developments and possibilitiesArticleFeb 2011MRPharmS Lecturer KEVIN M. G. TAYLOR PhD Duncan Q M CraigThe ability to target a drug specifically to its site of action has long been a goal in therapeuties. Liposomes (phospholipid vesicles) have been investigated as a means of achieving such selectivity and of prolonging the duration of drug activity. With reference to current and future clinical applications, this article outlines why liposomes are appropriate vehicles for drug delivery and describes the possible further development of liposome‐based pharmaceutical formulations. 1993 Royal Pharmaceutical Society of Great BritainViewShow abstractPeptide and protein drugs: I. Therapeutic applications, absorption and parenteral administrationArticleSep 1991INT J PHARMACEUTX.H. ZhouA LIWANPOIn this first part of a two-part review of peptide and protein drugs, the pertinent terminology is introduced and the therapeutic applications of those drugs summarised. Their absorption and the methodology commonly used for study on it are discussed. Approaches to optimising delivery of the peptide and protein drugs are highlighted.ViewShow abstractLiquid crystals and emulsions in the formulation of drug carriersArticleMar 2008CR CHIMPatrick Saulnier Nicolas Anton Béatrice Heurtault Jean-Pierre BenoitTargetting an encapsulated drug towards a diseased organ, with the possibility to control its release at the right place and at the right time, is one among numerous questions asked to the new nanotechnologies. We present a partial answer with the example of recently elaborated lipidic nanocapsules. Liquid crystals play a role in the preparation techniques, and possibly in the delivery mechanisms of the active principle in situ. We also know that liquid crystalline behaviours are involved at the membrane level and are essential in the cell machinery. Drug nanocarriers could find their way, as do viruses, in the liquid crystalline context of cell organization.ViewShow abstractIf your bullet s magic, what s your poison?: Antibody-Directed Liposomes, Liposome-Dependent Drugs, and how they were pursued in the Laboratory of Demetrios PapahadjopoulosArticleJan 1995J LIPOSOME RESTimothy D. HeathViewLIPOSOME – A NOVEL COLLOIDAL DRUG DELIVERY SYSTEMArticleFull-text availableJun 2011 Shobhit Kumar Pramod Sharma Mayank Bansal Rishabha MalviyaViewFunctionalization of immunostimulating complexes (ISCOMs) with lipid vinyl sulfones and their application in immunological techniques and therapyArticleFull-text availableDec 2012 Teresa Cruz BustosGloria González-González Julia Morales Sanfrutos Antonio OsunaImmunostimulating complexes (ISCOM)-type nanocapsules have been functionalized with lipid vinyl sulfones that anchor to them via the hydrophobic zone of their structure and can be charged with pharmacologically active molecules or macromolecules. These functionalized nanocapsules can incorporate protein A and bind to G immunoglobulins (IgGs) to make vehicles directed at the surface antigens of infectious agents, tumor cells, or receptor cells and deliver the encapsulated molecules in a highly specific way. They may be of particular use in pharmacological treatments with highly toxic molecules that should not be used in solution whenever it can be avoided. When bound to antibodies they can be used in biological processes that require the delivery or presentation of macromolecules to certain specific cells, in immunization processes for instance, or in diagnostic immunological techniques, as they are able to transport both the secondary antibodies and the reaction labels.We describe the preparation of ISCOMs, the binding to the ISCOMS of newly synthesized compounds composed of chain alkyl vinyl sulfone, and the subsequent binding of the vinyl-sulfone compounds to IgGs. Within this context, a compound deriving from cholesterol functionalized with vinyl sulfone and used together with cholesterol in varying proportions has been linked to the structure of the ISCOMs and bound to protein A-IgG. This functionalization in no way altered the form or structure of the ISCOMs and allowed the nanocapsules carrying the specific IgGs to bind to forms of Trypanosoma cruzi against which antibodies had been developed. The fact that functionalized ISCOMs containing antibodies could deliver actinomycin D directly to the parasite meant that the effective dose of the antibiotic could be reduced very significantly.We have developed ISCOM-type nanocapsules functionalized with lipid vinyl sulfone capable of anchoring to the surface of functional IgGs, which favors the recognition and transport of these nanocapsules precisely to certain kinds of cell.ViewShow abstractTargeting Cancer therapy in Mice by Use of Newly Developed Immunoliposomes Bearing AdriamycinArticleSep 2008J LIPOSOME RES Kiyoyasu FukushimaK HirataniMasaki HirotaJunzo SunamotoAbstract Polysaccharide-coated liposomes have been developed to improve the stability of conventional liposomes against biochemical and physicochemical stimuli. Pullulan (MW 5 × 104) was used as the polysaccharide. the mouse IgM monoclonal antibody (CSLEX 1) recognizes a sialosylated Lex, which is a tumor-specific antigen in athymic mice. the IgM antibody was reduced with cysteine to obtain the subunit (IgMs) that remained biologically active. the IgMs was accumulated in an antigen-positive tumor in vivo. Subsequently, it was conjugated with the pullulan-coated liposome to form an immunoliposome. Tissue distribution studies demonstrated that immunoliposomes were more efficiently targeted to an implanted tumor than to the polysaccharide-coated liposomes. This is accompanied by a drastic decrease in liver uptake of the immunoliposomes. Furthermore, adriamycin-encapsulated immunoliposomes in-hibited the growth of the implanted tumor more effectively than did the simple pulluian-coated liposomes.ViewShow abstractThe Influence of Tiered Layers of Surface-Grafted Poly(ethylene glycol) on Receptor−Ligand-Mediated Adhesion between Phospholipid Monolayer-Stabilized Microbubbles and Coated Glass BeadsArticleJan 2000LANGMUIRDennis H. Kim‡ and Alexander L. Klibanov David NeedhamThe goal of the current study is to measure the strength of specific adhesion between a prototypical phospholipid-stabilized ultrasound contrast agent, the surface of which has been derivatized with a ligand molecule, and a glass bead surface coated with the corresponding receptor. In particular, the role of surface \"architecture” (the size and density of surface-grafted molecules) in mediating adhesion is examined. The ligand surface density on bubble shells is varied by changing the mole ratios of shell components [lipid:poly(ethylene glycol) (PEG)ylated surfactant stabilizer:ligand−lipid] during preparation. Two receptor−ligand systems are tested:  avidin−biotin and antifluorescein−fluorescein. The central investigative method is a novel application of the micromanipulation technique in which an individual microbubble and a glass bead are captured by separate pipets in an aqueous environment and brought into adhesive contact with each other. Aspiration pressure applied by the bead pipet is incrementally increased until the level of force required to detach the bead from the bubble is exerted. The micromanipulation technique offers the advantage that a single adhesion event can be observed under controlled conditions, and the force required to effect bubble detachment is determined from pressure and system geometry. The strength of adhesion is examined as a function of composition and structure of the lipid shell and the receptor−ligand pair. The success of adhesion between surfaces is dependent on the availability of ligand proximal to the steric barrier of surface PEG. If the ligand is attached to the shell via a PEG spacer longer than that of the PEG stabilizer, then adhesion succeeds; if the ligand is not on an extended spacer, adhesion fails. Adhesion strength increases and plateaus with increasing ligand−lipid concentration. Such phenomena must be considered when engineering a targetable stabilized contrast agent.ViewShow abstractEnhancement of Both Intracellular Uptake and Antitumor Action of Cisplatinum on Human Neuroblastoma Cells by Encapsulation in LiposomesArticleAug 2005Canc SciYoshiro KamioHiroshi KatoTeruaki KishikawaRyo TanakaPhospholipid vesicles (phosphatidylcholine: phosphatidylserine: cholesterol=6:2:3 in molar ratio) with a small unilamellar structure were used as drug carriers for introducing cis-diamminedichloroplatinum (CDDP) into human neuroblastoma cells, IMR-32, GOTO, Nagai, and TGW. DNA synthesis of IMR-32 cells among the human neuroblastoma cell lines was inhibited most strongly by CDDP-liposomes. CDDP-liposomes dose-dependently inhibited the DNA synthesis of IMR-32 in a similar fashion to that observed with free CDDP, but the drug concentration required to induce 50% inhibition of DNA synthesis for CDDP-liposomes (IC50: 0.7 μg CDDP/ml) was 1/3 of the IC50 for free CDDP (2.0 μg CDDP/ml). In support of the marked growth-inhibitory action of CDDP-liposomes, the intracellular incorporation rate of CDDP-liposomes was 3-fold higher when liposomes were used as carriers than when free CDDP was directly applied. CDDP-liposomes showed a stronger growth inhibition on IMR-32 cells at a high cell density than at a low density in culture. CDDP-liposomes were rapidly incorporated by IMR-32 cells within 5 min, resulting in the inhibition of DNA synthesis to 40% of the control. Swiss albino mouse 3T3 cells were less inhibited by CDDP-liposomes than by free CDDP, suggesting that encapsulation of CDDP in liposomes decreases cytotoxicity to normal cells.ViewShow abstractLipid-Based Nanoparticles as Pharmaceutical Drug Carriers: From Concepts to ClinicArticleFull-text availableJan 2009 Anu Puri Kristin LoomisBrandon Smith Robert BlumenthalIn recent years, various nanotechnology platforms in the area of medical biology, including both diagnostics and therapy, have gained remarkable attention. Moreover, research and development of engineered multifunctional nanoparticles as pharmaceutical drug carriers have spurred exponential growth in applications to medicine in the last decade. Design principles of these nanoparticles, including nanoemulsions, dendrimers, nano-gold, liposomes, drug-carrier conjugates, antibody-drug complexes, and magnetic nanoparticles, are primarily based on unique assemblies of synthetic, natural, or biological components, including but not limited to synthetic polymers, metal ions, oils, and lipids as their building blocks. However, the potential success of these particles in the clinic relies on consideration of important parameters such as nanoparticle fabrication strategies, their physical properties, drug loading efficiencies, drug release potential, and, most importantly, minimum toxicity of the carrier itself. Among these, lipid-based nanoparticles bear the advantage of being the least toxic for in vivo applications, and significant progress has been made in the area of DNA/RNA and drug delivery using lipid-based nanoassemblies. In this review, we will primarily focus on the recent advances and updates on lipid-based nanoparticles for their projected applications in drug delivery. We begin with a review of current activities in the field of liposomes (the so-called honorary nanoparticles), and challenging issues of targeting and triggering will be discussed in detail. We will further describe nanoparticles derived from a novel class of amphipathic lipids called bolaamphiphiles with unique lipid assembly features that have been recently examined as drug/DNA delivery vehicles. Finally, an overview of an emerging novel class of particles (based on lipid components other than phospholipids), solid lipid nanoparticles and nanostructured lipid carriers will be presented. We conclude with a few examples of clinically successful formulations of currently available lipid-based nanoparticles.ViewShow abstractShow moreA General Method for the Introduction of Enzymes, by Means of Immunoglobulin-Coated Liposomes, into Lysosomes of Deficient CellsArticleFull-text availableFeb 1975P NATL ACAD SCI USA Gerald WeissmannD BloomgardenR KaplanD NaglePhagocytes of the smooth dogfish (Mustelus canis) contain no endogenous peroxidase within their lysosomes and constitute models for cells genetically deficient in lysosomal enzymes such as myeloperoxidase. We have obtained uptake of over 50% of exogenous horseradish peroxidase, provided the enzyme is exhibited to cells after incorporation into liposomes coated with heat-aggregated (62 degrees, 10 min), isologous IgM. Trapping of horseradish peroxidase (EC 1.11.1.7) by liposomes was established by chromatographic resolution (Sephadex G-200; Sepharose 2B and 4B) of free enzyme from that associated with liposomes; liposome-associated horseradish peroxidase, together with trapped markers of the aqueous compartment (glucose, CrO4 equals), were excluded, and free enzyme and markers were retained. Enzyme and marker trapping was not electrostatic, varied with the molar ratio of charged membrane components, and was reversed by detergent lysis (Triton X-100) of liposomes. Uptake at 30 degrees of aggregated IgM-coated liposomes containing trapped horseradish peroxidase exceeded that of free enzyme of 100-fold, and was more efficient than uptake of horseradish peroxidase presented in uncoated liposomes or in liposomes coated with native IgM. After phagocytosis, peroxidase-rich liposomes were localized exclusively in lysosomes of the phagocytes by ultrastructural histochemistry; the enzyme displayed over 50% latency to osmotic lysis. This method may prove to be of general use in the provision of exogenous enzymes to phagocytic cells genetically deficient in lysosomal hydrolases.ViewShow abstractTHE INTERACTION OF CATIONIC LIPOSOMES CONTAINING ENTRAPPED HORSERADISH PEROXIDASE WITH CELLS IN CULTUREArticleNov 1974J CELL BIOLWayne E. MageeCationic liposomes composed of sphingomyelin, cholesterol, and stearylamine were prepared with horseradish peroxidase trapped inside. Stable particles were formed in which 10–12% of the enzymic activity appeared to be located at, or near, the outer surface of the liposome. Adsorption and uptake of liposomes by HeLa cells were followed cytochemically by electron microscopy and quantitated by enzyme assay and by the distribution and fate of particles labeled with [14C]cholesterol and [125I]horseradish peroxidase. The particles were adsorbed by HeLa cells at least 300 times as efficiently as was free horseradish peroxidase. Many of the particles remained at the cell surface, but numerous membrane-bound cytoplasmic inclusions were observed to contain peroxidase-staining material. In addition, many areas of the cell membrane gave a positive staining reaction. It was concluded that many particles (presumably the larger ones) did not gain access to the interior of the cells, many were phagocytized, and some enzyme was transferred to the cell membrane, perhaps as a result of fusion of the liposomal membrane with the cell membrane.ViewShow abstractLiposomes containing chelating agents. Cellular penetration and a possible mechanism of metal removalArticleMay 1975J CELL BIOLY E RahmanB J WrightElectron microscope studies were done on mouse liver, from 5 min to 8 wk after an intravenous injection of liposomes containing ethylenediaminetetraacetic acid (EDTA). Livers of mice receiving an injection of liposomes containing KCL instead of EDTA or an injection of a solution of EDTA were also examined. Liposomes were shown to be phagocytized by hepatocytes as well as by Kupffer cells within minutes after the injection. Initially, there was a close contact between the liposomal membrane and the cellular membrane, followed by an invagination of the latter and the formation of a distinct vesicle surrounding a single liposome or a cluster of several liposomes. No fusion between the liposomal membrane and the cell membrane was observed. Between 15 min and 6 h after liposome injection, the Kupffer cells were found to have an increased number of lysosomes and autophagic vacuoles. Within the latter, morphologically intact liposomes or remnants of liposomes could be seen. At 12 h after injection, a striking increase in macrophages was observed in the liver sinusoids of EDTA-liposome-injected mice, but not in those of KCl-liposome-injected mice. Within the macrophages, remnants of liposomes occasionally could be observed. However, the origin and the physiological role of these cells are unknown. In the hepatocytes, morphological changes were first observed 24 h after injection; there were large numbers of autophagic vacuoles, and some cells showed extensive areas of focal cytoplasmic degeneration. The morphology of the liver cells returned to normal about 7 days after injection. No morphological changes were observed in livers of mice receiving EDTA solution without liposomes. A possible mechanism by which the liposome-encapsulated chelating agents can successfully remove intracellular toxic metals is discussed. The use of liposomes as carriers seems to be a useful tool for intracellular delivery of chelating agents or drugs in general.ViewShow abstractThe effect of particle size and charge on the clearance rates of liposomes and liposome encapsulated drugsArticleMay 1975BIOCHEM BIOPH RES COR L JulianoD StampHeterogeneous populations of liposomes were cleared from the rat bloodstream in a complex manner, with a rapid phase and a slow phase of removal. Small unilamellar vesicles were cleared less rapidly than were large multilamellar ones. Particle charge was also an important determinant of clearance since neutral and positively charged unilamellar liposomes were cleared less rapidly than were unilamellar negatively charged ones. Liposome samples homogeneous in size exhibited simple exponential clearance kinetics rather than the complex kinetics exhibited by heterogeneous samples. A liposome encapsulated drug (3H-colchicine) was cleared from the circulation at a rate corresponding to the removal of the liposomal vesicle, and different from the rate of removal of free drug.ViewShow abstractEntrapment of proteins in liposomes prevents alergic reactions in preimnumized miceArticleOct 1974FEBS LETT Gregory GregoriadisAnthony C. AllisonViewA hypothesis for I-cell disease: Defective hydrolases that do not enter lysosomesArticleDec 1972BIOCHEM BIOPH RES COScot HickmanElizabeth F. NeufeldSkin fibroblasts cultured from patients with I-cell disease (\"I-cells”) are markedly deficient in several lysosomal hydrolases, though these enzymes are found in surrounding medium. This situation is not brought about by increased lysosomal leakage, since I-cells were found as retentive of ingested enzymes (β-glucuronidase and α-L-iduronidase) as cells of other genotypes. On the other hand, hydrolases from I-cell medium were found only one-fifth to one-tenth as effective as their normal counterparts in experiments that involve uptake of the enzymes from the medium: correction of Hurler cells by α-L-iduronidase, correction of β-glucuronidase deficient cells by β-glucuronidase, and direct measurement of uptake of N-acetyl β-glucosaminidase by fibroblasts deficient in that enzyme.We suggest that the packaging of lysosomal enzymes requires their secretion followed by specific recognition and uptake. The I-cell mutation would interfere with this process by altering the recognition site on the hydrolases.ViewShow abstractDistribution and Fate of Synthetic Lipid Vesicles in the Mouse: A Combined Radionuclide and Spin Label StudyArticleOct 1974P NATL ACAD SCI USAI. Ross McDougallJ K DunnickM G McNameeJoseph P. KrissSingle compartmental spherules of various lipid constituents (vesicles), enclosing 99mTcO4⁻ as a radioactive marker, were injected intravenously into C3H mice, and the distribution of radioactivity was studied. About 25% of the administered radioactivity was present in the liver 5 min and 30 min after the injection of vesicles composed of phosphatidylcholine and gangliosides, which were sonicated for 5 min (standard preparation). About 10-20% of the radioactivity remained in the circulation. By use of a nonradioactive spin label (tempocholine) enclosed within vesicles, intact vesicles were demonstrated in the circulation for 46 min after intravenous injection. The distribution of radioactivity from 99mTcO4⁻ inside vesicles is very different from that of free 99mTcO4⁻ or of 99mTc sulfur colloid.Increase in the length of sonication or incorporation of cholesterol into the wall of the vesicles enhanced hepatic levels and reduced blood levels of radioactivity. These same manipulations also slowed the rate of transfer of 99mTcO4⁻ out of vesicles in dialysis experiments in vitro. Addition of phosphatidic acid, phosphatidylethanolamine, or phosphatidylserine to the standard constituents did not greatly alter the distribution of radioactivity in vivo but did increase the number and type of active coupling sites on the outside of the vesicle. The results indicate that vesicles might be valuable as carriers of diagnostic or therapeutic agents.ViewShow abstractLiposomes as immunological adjuvantsArticleDec 1974NATUREAG Allison Gregory GregoriadisADJUVANTS are widely used to increase antibody formation in experimental animals, for example, Freund s incomplete adjuvant, a water-in-oil emulsion containing the antigen, and Freund s complete adjuvant, which is the same but with killed tubercle bacilli. These adjuvants cannot be used in man because the mineral oil base is not degraded and persists at the injection site. Particularly with the complete adjuvant, unacceptable granulomas can be formed. There is real need for a safe and effective adjuvant for use in human immunisation programmes.ViewShow abstractControl of the Rate of Hepatic Uptake and Catabolism of Liposome‐Entrapped Proteins Injected into Rats. Possible Therapeutic ApplicationsArticleSep 1974Eur J Biochem Gregory GregoriadisDiane E. Neerunjun131I- or 125I-labelled albumin and β-fructofuranosidase were entrapped in liposomes composed of phosphatidylcholine, cholesterol and a charged lipid (molar ratio 7:2:1). Investigations on the fate of such liposomes injected into rats revealed the following.1. Initially there is an increased rate of removal from plasma (rapid phase) followed by a decreased one (slow phase). The rate of removal during the rapid phase was highest for negatively charged liposomes and lowest for positively charged liposomes with neutral liposomes in between. Uniform rates of removal, regardless of charge, were obtained during the slow phase.2. The rate of hepatic uptake of such liposomes paralleled that observed for their removal from plasma during the rapid phase.3. Concurrent administration of a large quantity of positively charged liposomes and of a smaller quantity of negatively charged liposomes led to a diminution of the rapid phase of the latter suggesting a common site of uptake for liposomes of either charge.4. Blockade of the reticuloendothelial system with carbon led to an increased hepatic localization of liposomes during the rapid phase suggesting a bimodal uptake of liposomes with both the Kupffer and the liver parenchymal cells involved.5. Cross-linking of liposome-entrapped albumin and β-fructofuranosidase increased the stability of the latter and following injection into rats rendered both proteins less vulnerable to degradation by the liver lysosomal enzymes.6. The possibility of controlling both the rate of removal from plasma and catabolism of liposome-entrapped proteins adds more scope to the use of liposomes in therapy.ViewShow abstractUse of simple concentration gradients for the fractionation of human serum proteins on DEAE-cellulose, with especial reference to the isolation of albumin, prealbumin, haemopexin and transferrinArticleOct 1973J CHROMATOGR AD B RamsdenL N LouisThe possibility of using simple concentration gradients, formed by an automatic gradient former, was explored for the fractionation of human serum. Especial reference was paid to the isolation of albumin, prealbumin, haemopexin and transferrin. Prealbumin was most clearly resolved from albumin by a linear gradient whilst haemopexin and transferrin were partially resolved using a non-linear gradient with a very shallow initial rise in concentration. The disadvantages of the system and how these may be minimized using gamma emitters were pointed out.ViewShow abstractDrug entrapment in liposomesArticleDec 1973FEBS LETT Gregory GregoriadisViewPhospholipid-protein interactions: Membrane permeability correlated with monolayer penetration ArticleJul 1971Biochim Biophys Acta Harold K KimelbergDemetrios PapahadjopoulosThe effectiveness of various soluble proteins in increasing the permeability of phospholipid membranes was found to be directly correlated with their ability to \"penetrate” monomolecular films of the same phospholipids. We propose that the increase in permeability depends on hydrophobic associations of the protein with the phospholipid which are facilitated by initial electrostatic binding.ViewShow abstractEfficient Trace-Labelling of Proteins with IodineArticleAug 1958NATUREA S McFARLANEIN the methods of iodination currently used only the cationic portion of the iodine molecule becomes bound to the ring structure of tyrosine, so that the theoretical efficiency of labelling is 50 per cent. In practice, efficiencies are always lower than this and may be only a few per cent when the ratio of iodine to protein used is less than one atom per molecule. Values greater than 50 per cent can be obtained by adding oxidizing agents to liberate iodine from iodide, but most if not all of these appear to affect adversely the properties of the labelled protein.ViewShow abstractRecommended publicationsDiscover moreArticleHeterogeneity of acid β-galactosidase from rabbit kidneyFebruary 1987 · International Journal of BiochemistryMaría Páez de la Cadena Joel Santiago CabezasM N Pérez-González1. Rabbit kidney acid beta-galactosidase can be resolved into three peaks (named A3, A2 and A1) by gel-filtration chromatography. Their estimated molecular weights were: more than 250,000, 150,000 and 17,000 respectively. 2. The purified acid form appeared as a single band of protein (Mr = 28,000) on electrophoresis in the presence of sodium dodecyl sulphate, suggesting that forms A3 and A2 are ... [Show full abstract] multimeric forms of beta-galactosidase A1. 3. Treatment with neuraminidase from Clostridium perfringens converts form A3 into a more basic form. This phenomenon occurs also when this form is stored for a week at 4 degrees C and parallels its disaggregation. 4. The data suggest that the sialic acids present in the multimeric forms are involved in the aggregation of the acidic form of beta-galactosidase.Read moreArticleDifferences between the N acetyl hexosaminidase isozymes in serum and tissuesFebruary 1974 · Annals of Human Genetics Dallas M Swallow Dennis C StokesG CorneyHarry HarrisThe predominant isozyme of N acetyl β d hexosaminidase (NAGA) found in serum, NAGA A , has been shown to have a faster electrophoretic mobility than NAGA A from extracts of all other tissues and body fluids tested. NAGA A from serum can be converted into a form with B mobility by the action of the enzyme neuraminidase (preparations from Vibrio cholerae obtained from B.D.H. and from ... [Show full abstract] Clostridium perfringens obtained from Sigma) but NAGA A from tissue extracts is in contrast resistant to the action of this enzyme. NAGA A from tissue extracts can however be converted into a form with B mobility by crude preparations of receptor destroying enzyme (R.D.E.). This conversion is shown not to be due to neuraminidase and is apparently non enzymic. The substance concerned is evidently a low molecular weight component of the preparation as demonstrated by dialysis and ultrafiltration experiments. The effect persists after heating the preparation for 30 min. at 100°C., autoclaving it under 18 lb. pressure for 10 min. or boiling for 1 min. in strong acid or alkali. N acetyl hexosaminidase activity was assayed in a series of 87 serum samples from pregnant women and 90 sera taken in the first few days post partum. A progressive rise in average activity through pregnancy was observed and a rapid decline following delivery. Electrophoretic examination of these samples showed that the extra isozyme, P, was present in all of the 74 samples tested (6 - 41 wk gestation). A similar isozyme has also been seen in occasional serum samples from non pregnant individuals but no such band was seen in a large number of extracts from placentas, tissues from fetuses as well as adults, nor in the few samples from three other enzyme sources of pregnant individuals. The possible source of the serum isozymes of N acetyl hexosaminidase, A and P, is discussed. An electrophoretic survey of 1937 placental extracts was made (from Europeans and other ethnic groups) and no genetic variants were found.Read moreArticleDemonstration of a Circulating Factor Regulating Blood Platelet Production using 35S-Sulfate in Rats...October 1970 · Proceedings of The Society for Experimental Biology and MedicineG W CooperB CooperC Y ChangPlatelet counts and 35S-sulfate incorporation were studied in rats and mice following injection of saline or homologous plasma from normal or platelet-depleted animals, Donor rats were treated with antiplatelet serum 5–18 hr before sarcifice, and donor mice were injected with neuraminidase 40 hr before exsanguination. To prevent the injection of platelet antibody, the simulated and control ... [Show full abstract] plasmas were either boiled at acid pH for 10–15 min, or precipitated with goat antirabbit gamma globulin antiserum (GAGGA). The sulfate incorporation into platelets of animals given plasma from depleted donors was significantly increased over control values to levels as high as 116%. These data demonstrated the existence of thrombopoietin control over platelet production. The radiosulfate incorporation method appeared to be more sensitive than assays making use of platelet counts alone.Read moreArticleBacterial and Viral Sialidases: Contribution of the Conserved Active Site Glutamate to CatalysisDecember 2011 · Biochemistry Jefferson ChanJacqueline N WatsonApril Lu[...]Andrew J. BennetMutagenesis of the conserved glutamic acid of influenza type A (E277) and Micromonospora viridifaciens (E260) sialidases was performed to probe the contribution of this strictly conserved residue to catalysis. Kinetic studies of the E260D and E260C M. viridifaciens mutant enzymes reveal that the overall mechanism of action has not changed. That is, the mutants are retaining sialidases in which ... [Show full abstract] glycosylation and deglycosylation are rate-limiting for k(cat)/K(m) and k(cat), respectively. The solvent kinetic isotope effect and proton inventory on k(cat) for the E260C mutant sialidase provide strong evidence that the newly installed cysteine residue provides little catalytic acceleration. The results are consistent with the conserved aspartic acid residue (D92) becoming the key general acid/base residue in the catalytic cycle. In addition, the E277D mutant influenza type A sialidase is catalytically active toward 4-nitrophenyl α-D-sialoside, although no measurable hydrolysis of natural substrates was observed. Thus, mutating the glutamate residue (E277) to an aspartate increases the activation free energy of hydrolysis for natural substrates by 22 kJ/mol.Read moreLooking for the full-text?You can request the full-text of this article directly from the authors on ResearchGate.Request full-textAlready a member? Log in ResearchGate iOS AppGet it from the App Store now.InstallKeep up with your stats and moreAccess scientific knowledge from anywhere orDiscover by subject areaRecruit researchersJoin for freeLoginEmail Tip: Most researchers use their institutional email address as their ResearchGate loginPasswordForgot password? Keep me logged inLog inorContinue with GoogleWelcome back! Please log in.Email · HintTip: Most researchers use their institutional email address as their ResearchGate loginPasswordForgot password? Keep me logged inLog inorContinue with GoogleNo account? Sign upCompanyAbout usNewsCareersSupportHelp CenterBusiness solutionsAdvertisingRecruiting© 2008-2021 ResearchGate GmbH. All rights reserved.TermsPrivacyCopyrightImprint