Liposomal Drug Delivery Systems Research Articles

A dual-mediated liposomal drug delivery system targeting the brain: rational construction, integrity evaluation across the blood-brain barrier, and the transporting mechanism to glioma cells.

As the global population ages, cancer rates increase worldwide, and degenerative diseases of the central nervous system (CNS), brain tumors, and inflammation threaten human health more frequently. We designed a dual-mediated (receptor-mediated and adsorption-mediated) liposome, named transferrin–cell penetrating peptide–sterically stabilized liposome (TF-CPP-SSL), to improve therapy for gliomas through combining molecular recognition of transferrin receptors (TF-Rs) on the blood–brain barrier (BBB) and glioma cells with the internalization and lysosomal escaping ability of CPP. Based on the systematic investigation of structure–activity relations on the cellular level, we constructed TF-CPP-SSL rationally by conjugating TF and CPP moieties to the liposomes via PEG3.4K and PEG2.0K, respectively, and found the optimum densities of TF and CPP were 1.8% and 4%, respectively. These liposomes had the highest targeting efficacy for brain microvascular endothelial cell and C6 cell uptake but avoided capture by normal cells. Fluorescence resonance energy transfer technology and coculture models of BBB and glioma C6 cells indicated that TF-CPP-SSL was transported across the BBB without drug leakage, liposome breakup, or cleavage of ligand. TF-CPP-SSL offered advantages for crossing the BBB and entering into glioma C6 cells. Real-time confocal viewing revealed that TF-CPP-SSL was entrapped in endosomes of glioma C6 cells and then escaped from lysosomes successfully to release the liposomal contents into the cytosol. Entrapped contents, such as doxorubicin, could then enter the nucleus to exert pharmacological effects.

Nanoliposomal artemisinin for the treatment of murine visceral leishmaniasis

Visceral leishmaniasis (VL) is a fatal, vector-borne disease caused by the intracellular protozoa of the genus Leishmania. Most of the therapeutics for VL are toxic, expensive, or ineffective. Sesquiterpenes are a new class of drugs with proven antimicrobial and antiviral activities. Artemisinin is a sesquiterpene lactone with potent antileishmanial activity, but with limited access to infected cells, being a highly lipophilic molecule. Association of artemisinin with liposome is a desirable strategy to circumvent the problem of poor accessibility, thereby improving its efficacy, as demonstrated in a murine model of experimental VL. Nanoliposomal artemisinin (NLA) was prepared by thin-film hydration method and optimized using Box–Behnken design with a mean particle diameter of 83±16 nm, polydispersity index of 0.2±0.03, zeta potential of −27.4±5.7 mV, and drug loading of 33.2%±2.1%. Morphological study of these nanoliposomes by microscopy showed a smooth and spherical surface. The mechanism of release of artemisinin from the liposomes followed the Higuchi model in vitro. NLA was free from concomitant signs of toxicity, both ex vivo in murine macrophages and in vivo in healthy BALB/c mice. NLA significantly denigrated the intracellular infection of Leishmania donovani amastigotes and the number of infected macrophages ex vivo with an IC50 of 6.0±1.4 µg/mL and 5.1±0.9 µg/mL, respectively. Following treatment in a murine model of VL, NLA demonstrated superior efficacy compared to artemisinin with a percentage inhibition of 82.4%±3.8% in the liver and 77.6%±5.5% in spleen at the highest dose of 20 mg/kg body weight with modulation of cell-mediated immunity towards protective Th1 type. This study is the first report on the use of a liposomal drug delivery system for artemisinin as a promising alternative intervention against VL.

Peptide-22 and Cyclic RGD Functionalized Liposomes for Glioma Targeting Drug Delivery Overcoming BBB and BBTB.

Chemotherapy outcomes for the treatment of glioma remain unsatisfied due to the inefficient drug transport across BBB/BBTB and poor drug accumulation in the tumor site. Nanocarriers functionalized with different targeting ligands are considered as one of the most promising alternatives. However, few studies were reported to compare the targeting efficiency of the ligands and develop nanoparticles to realize BBB/BBTB crossing and brain tumor targeting simultaneously. In this study, six peptide-based ligands (Angiopep-2, T7, Peptide-22, c(RGDfK), D-SP5 and Pep-1), widely used for brain delivery, were selected to decorate liposomes, respectively, so as to compare their targeting ability to BBB or BBTB. Based on the in vitro cellular uptake results on BCECs and HUVECs, Peptide-22 and c(RGDfK) were picked to construct a BBB/BBTB dual-crossing, glioma-targeting liposomal drug delivery system c(RGDfK)/Pep-22-DOX-LP. In vitro cellular uptake demonstrated that the synergetic effect of c(RGDfK) and Peptide-22 could significantly increase the internalization of liposomes on U87 cells. In vivo imaging further verified that c(RGDfK)/Pep-22-LP exhibited higher brain tumor distribution than single ligand modified liposomes. The median survival time of glioma-bearing mice treated with c(RGDfK)/Pep-22-DOX-LP (39.5 days) was significantly prolonged than those treated with free doxorubicin or other controls. In conclusion, the c(RGDfK) and Peptide-22 dual-modified liposome was constructed based on the targeting ability screening of various ligands. The system could effectively overcome BBB/BBTB barriers, target to tumor cells and inhibit the growth of glioma, which proved its potential for improving the efficacy of chemotherapeutics for glioma therapy.

Innovations in Liposomal DDS Technology and Its Application for the Treatment of Various Diseases.

Liposomes have been widely used as drug carriers in the field of drug delivery systems (DDS), and they are thought to be ideal nano-capsules for targeting DDS after being injected into the bloodstream. In general, DDS drugs meet the needs of aged and super-aged societies, since the administration route of drugs can be changed, the medication frequency reduced, the adverse effects of drugs suppressed, and so on. In fact, a number of liposomal drugs have been launched and used worldwide including liposomal anticancer drugs, and these drugs have appeared on the market owing to various innovations in liposomal DDS technologies. The accumulation of long-circulating liposomes in cancer tissue is driven by the enhanced permeability and retention (EPR) effect. In this review, liposome-based targeting DDS for cancer therapy is briefly discussed. Since cancer angiogenic vessels are the ideal target of drug carriers after their injection and are critical for cancer growth, damaging of these neovessels has been an approach for eradicating cancer cells. Also, the usage of liposomal DDS for the treatment of ischemic stroke is possible, since we observed that PEGylated liposomes accumulate in the site of cerebral ischemia in transient middle cerebral artery occlusion (t-MCAO) model rats. Interestingly, liposomes carrying neuroprotectants partly suppress ischemia/reperfusion injury of these model rats, suggesting that the EPR effect also works in ischemic diseases by causing an increase in the permeability of the blood vessel endothelium. The potential of liposomal DDS against life-threatening diseases might thus be attractive for supporting long-lived societies.

Evaluation of liposomal carnosine in adjuvant arthritis.

Liposomal carnosine could overcome the problems associated with direct application of this peptide. Anti-inflammatory and antioxidant effects of liposomal and non-liposomal carnosine in adjuvant arthritis were compared. The experiments were done on healthy animals, untreated arthritic animals, arthritic animals with oral administration of carnosine, and with subcutaneous administration of liposomal carnosine, both administered in the same daily dose of 150 mg/kg b.w. during 28 days. Carnosine reduced hind paw volume on day 28. Both forms markedly decreased interleukin-1β, matrix metalloproteinase-9 and monocyte chemoattractant protein-1 (MCP-1) in plasma on day 14. Only liposomal carnosine reduced significantly MCP-1. Malondialdehyde, 4-hydroxynonenal, resistance to Fe2+-induced oxidation and protein carbonyls were significantly corrected after administration of any form of carnosine. Liposomal carnosine corrected more effectively the oxidative stress in plasma than did carnosine. In brain tissue, our results showed protective ability of both forms of carnosine against oxidation of proteins and lipids. They also corrected the resistance to Fe2+-induced oxidation in arthritic animals. We found that only liposomal carnosine decreased the mRNA expression of inducible nitric oxide synthase in cartilage tissue. It can be concluded that the liposomal drug-delivery system is improving the pharmacological properties of carnosine administered in arthritis.

Vaginal Delivery of Benzydamine Hydrochloride through Liposomes Dispersed in Mucoadhesive Gels.

Liposomal vaginal drug delivery systems are important strategy in the treatment of both topical and systemic diseases. The aim of this study was to develop a vaginal delivery system for benzydamine hydrochloride (BNZ) loaded liposomes dispersed into mucoadhesive gels. The delivery system was also designed for a once a day dosage and to obtain controlled release of the BNZ. For this purpose BNZ containing gel formulations using hydroxypropyl methylcellulose (HPMC) K100M and Carbopol® 974P, which are composed of polymers that show promising potential as mucoadhesive vaginal delivery systems, were developed. In addition, a BNZ containing liposome formulation was developed for vaginal administration. To improve the vaginal retention time, liposome was incorporated in HPMC K100M and Carbopol® 974P gel formulations. This system is called lipogel. The developed BNZ liposomes have a slightly negative zeta potential (-1.50±0.16 mV), a 2.25±0.009 µm particle size and a 34% entrapment efficiency. These gels and lipogels have appropriate pH, viscosity, textural properties and mucoadhesive value for vaginal administration. Lipogels were found to be the best formulations for in vitro diffusion and ex vivo mucoadhesion. The work of mucoadhesion obtained from liposomes was in the range of 0.027±0.045 and 0.030±0.017 mJ/cm2, while the value obtained from lipogels was between 0.176±0.037 and 0.243±0.53 mJ/cm2. N1 and N2 lipogel formulations diffused 57 and 67% of BNZ respectively at the end of 24 h. Moreover, a higher mucoadhesion, which increases drug residence time in comparison to liposomes, could improve BNZ efficacy. In conclusion, BNZ mucoadhesive vaginal lipogel formulations can be promising alternatives to traditional dosage forms for vaginal topical therapy.

Examination the Properties of Lipopeptide Liposomes Modified by Glycoconjugates

Development of transport systems possessing definite physicochemical and biological properties aimed at the targeted delivery of biologically active compounds remains nowadays among urgent problems of the medicine. In this work we made physical chemical and biological tests liposomal drug delivery systems modified with glycolipids for target properties.

Liposomal Drug Delivery System for Cancer Therapy: Advancement and Patents.

In this review article, authors reviewed about the liposomes which are amongst various drug delivering systems for the delivery of the therapeutic agents at the target site. Advances in liposomal drug delivery systems for the cancer therapy have enhanced the therapeutic levels of the anticancer moieties. Liposomes show promising action on the tumor by incorporating less amount of drug at the target site, with minimum toxic effect and maximum therapeutic effect and thereby enhancing the bioavailability. Liposome-based drug delivery systems provide the potential to elevate the effect of drug concentration in tumor cells. Manuscript briefly describes the role of liposomes in cancer therapy and various patents based on the same.

Study of the pH-sensitive mechanism of tumor-targeting liposomes

Currently, the phosphatidylethanolamine-based, pH-sensitive, liposome drug-delivery system has been widely developed for efficient, targeted cancer therapy. However, the mechanism of pH sensitivity was unclear; it is a main obstacle in controlling the preparation of pH-sensitive liposomes (PSLs).Therefore, our research is aimed at clarifying the pH-response mechanism of the various molecules that compose liposomes. We chose the small pH-sensitive molecules oleic acid (OA), linoleic acid (LA) and cholesteryl hemisuccinate (CHEMS) and the fundamental lipids cholesterol and phosphatidylethanolamine (PE) as test molecules. The PSLs were prepared using the thin-film hydration method and characterized in detail at various pH values (pH 5.0, 6.0 and 7.4), including particle size, ζ-potential, drug encapsulation efficiency and drug loading. The surface structure was observed by transmission electron microscopy (TEM), and the electrical conductivity of the liposome dispersion was also tested. The calorimetric analysis was conducted by Nano-differential scanning calorimetry (Nano-DSC). The in vitro drug release profile showed that PSLs exhibit good pH sensitivity. At neutral pH, the particle size was approximately 150nm, and it dramatically increased at pH 5.0. The ζ-potential increased as the pH decreased. The Nano-DSC results showed that cholesterol and CHEMS can both increase the stability and phase transfer temperature of PSLs. Conductivity increased to a maximum at pH 5.0 and was rather low at pH 7.4. In conclusion, results show that the three kinds of liposomes have pH responsive release characteristics in acidic pH. The OA-PSLs have a pH sensitive point of 5. Since CHEMS has a cholesterol-like structure, it can stabilizes the phospholipid bilayer under neutral conditions as shown in the Nano-DSC data, and because it has a special steroidal rigid structure, it exhibits better pH response characteristics under acidic conditions.

Liposomal drug delivery systems for targeted cancer therapy: is active targeting the best choice?

Liposomes are biodegradable and biocompatible self-forming spherical lipid bilayer vesicles. They can encapsulate and deliver one or more hydrophobic and hydrophilic therapeutic agents with poor therapeutic indices to tumor sites. Properties such as lipid bilayer fluidity, charge, size and surface hydration can be modified to extend liposome circulation time in the bloodstream and enhance efficacy. The focus of this review is on ligand-conjugated liposomes and their potential application in tumor-targeted delivery. Ligand-conjugated liposomes are designed to target receptors which are overexpressed on tumor cells to decrease drugs side effects by enhancing their selective delivery to tumor site. Despite the extensive research in this area, no small molecule ligand-conjugated liposome has been approved up to date for cancer therapy.

VEGF- and VEGFR2-Targeted Liposomes for Cisplatin Delivery to Glioma Cells

Targeted delivery of anticancer drugs to brain tumors, especially glioblastoma multiforme, which is the most frequent and aggressive type, is one of the important objectives in nanomedicine. Vascular endothelial growth factor (VEGF) and its receptor type II (VEGFR2) are promising targets because they are overexpressed by not only core tumor cells but also by migrated glioma cells, which are responsible for resistance and rapid progression of brain tumors. The purpose of the present study was to develop the liposomal drug delivery system combining enhanced loading capacity of cisplatin and high binding affinity to glioma cells. This was achieved by using of highly soluble cisplatin analogue, cis-diamminedinitratoplatinum(II), and antibodies against the native form of VEGF or VEGFR2 conjugated to liposome surface. The developed drug delivery system revealed sustained drug release profile, high affinity to antigens, and increased uptake by glioma C6 and U-87 MG cells. Pharmacokinetic study on glioma C6-bearing rats revealed prolonged blood circulation time of the liposomal formulation. The above features enabled the present drug delivery system to overcome both poor pharmacokinetics typical for platinum formulations and low loading capacity typical for conventional liposomal cisplatin formulations.

Theoretical Assessment of Fluorinated Phospholipids in the Design of Liposomal Drug-Delivery Systems.

Fluorinated phospholipid analogues are investigated as potential substrates for phospholipase A2 (PLA2) using classical molecular dynamics simulations and quantum mechanics/density functional theory calculations. The fluorinated phospholipid analogues are α-fluoro (HF-ProAEL) and α,α-difluoro (F2-ProAEL) conjugates of (R)-1-O-hexadecyl-2-palmitoyl-sn-glycero-3-phoshocholineglycerol (ProAEL). Our results provide a theoretical assessment of the potential usefulness of these fluorinated lipids in the rational design of liposomal drug-delivery systems. The α-fluorine-substituted phospholipid analogues are found to be substrates for secretory PLA2, with sufficient accessibility of water to the active site to allow for enzymatic hydrolysis. Because of the inherently less stable nature of HF-ProAEL and F2-ProAEL when compared to that of ProAEL, the hydrolytic reaction is predicted to occur at a progressively faster rate; the more electronegative substituent at the α-position effectively lowers the energy barrier for hydrolysis. We conclude that the partially fluorinated phospholipid analogues facilitate rational design of liposomal vesicles of phospholipid mixtures with desirable physicochemical properties and that are still subjects for important and pharmaceutically proven drug-delivery mechanisms.

In vitro toxicity of cationic micelles and liposomes in cultured human hepatocyte (HepG2) and lung epithelial (A549) cell lines

The aim of this study was to compare the effects of cationic micelle and liposome drug delivery systems on liver and lung cells in a toxicological in vitro screening model, with observations on cytotoxicity and genotoxicity. A screening battery was established for assessment of a broad range of parameters related to adverse effects. Clear concentration response effects were observed related to impairment of mitochondrial function, membrane integrity and oxidative stress markers, but no effect was observed on genotoxicity. The adverse effects were highest for the liposomes. The High Content Screening seems optimal for initial screening of adverse effects, and combined with standard cytotoxicity measurements initial screening can be performed for predictive toxicological screening.

Cholesteryl to improve the cellular uptake of polymersomes within HeLa cells

The need to develop a greater understanding of drug delivery systems has arisen through the development of alternative biological based therapeutics. Drug delivery systems need to adapt and respond to this increasing demand for cellular transportation of highly charged species. Polymersomal drug delivery systems have displayed great potential and versatility for such a task. In this manuscript we present the synthesis, characterisation and biological evaluation of six amphiphilic random co polymers with varying amounts of cholesteryl (0⿿39%wt) before the subsequent formation into polymersomes. The polymersomes were then analysed for size, zeta potential, encapsulation efficiency, release kinetics and cellular uptake. Results confirmed that the polymersome containing 12%wt cholesteryl polymer displayed a ten-fold increase in cellular uptake of Fitc-CM-dextran when compared to un-encapsulated drug, crossing the cellular membrane via endocytosis. The size of these vehicles ranged between 100 and 500nm, zeta potential was shown to be neutral at ⿿0.82mV ±0.2 with encapsulation efficiencies in the region of 60%. The ease of adaptability and preparation of such systems renders them a viable alternative to liposomal drug delivery systems.

Abstract 3907: Enhanced chemotherapeutic effect with matrix metalloproteinase sensitive liposomes

Abstract Introduction: Drug bioavailability following intra-tumoral accumulation is a major challenge in existing drug delivery systems. A site-specific trigger for obtaining drug release specifically in tumor tissue would overcome this problem and enhance the antitumor effect of the carried drug. Our aim was to develop a new drug delivery platform based on liposomes that are sensitive to matrix metalloproteinases (MMPs). Methods: In the present work, we have designed a matrix metalloproteinase (MMP)-sensitive liposomal drug delivery system encapsulating oxaliplatin, which by tumor-specific enzymatic dePEGylation allows for controlling the precision of drug release. The dePEGylation is provided by a cholesterol-anchored PEGylated lipopeptide containing a short peptide sequence cleavable by MMP-2 and MMP-9. These MMP-sensitive liposomes are designed to make a charge-reversal transformation upon encountering MMPs in the tumor environment. The surface charge of the liposome turns from slightly negative to positive, resulting in cationic liposomes. In vitro cellular uptake of the liposomes was assessed using flow cytometry and ICP-MS, and further confirmed by confocal microscopy in CT26 and HT1080 cell lines. In vivo studies was evaluated in a syngeneic murine model of MMP-positive CT26 colon cancer. Results: We successfully formulated MMP-sensitive, oxaliplatin encapsulated liposomes and characterized their zeta potential, size, stability and encapsulation efficiency. The results showed uniformly dispersed particles, and the charge-reversal properties were confirmed as the surface charge changed from slightly negative to distinct positive upon enzymatic cleavage generating cationic liposomes. These MMP-sensitive liposomes were evaluated in vitro and in vivo with a high correlation. In vivo studies showed a prolonged circulation profile with minimal leakage, and similar accumulation in tumors as conventional Stealth liposomes. Efficacy experiment in the same model demonstrated significantly improved antitumor activity relative to free oxaliplatin, and with a superior effect compared to the conventional Stealth liposomes. Conclusion: With this study, we establish a promising liposomal drug delivery platform for the carriage and release of numerous anticancer drugs into the microenvironment of an MMP-positive tumor. Citation Format: Rikke Y. Brogaard, Rasmus Eliasen, Fredrik Melander, Anders E. Hansen, Andreas Kjær, Thomas Lars Andresen. Enhanced chemotherapeutic effect with matrix metalloproteinase sensitive liposomes. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3907.

Needle-free jet injection of intact phospholipid vesicles across the skin: a feasibility study.

Needle-free liquid jet injectors are devices developed for the delivery of pharmaceutical solutions through the skin. In this paper, we investigated for the first time the ability of these devices to deliver intact lipid vesicles. Diclofenac sodium loaded phospholipid vesicles of two types, namely liposomes and transfersomes, were prepared and fully characterized. The lipid vesicles were delivered through a skin specimen using a jet injector and the collected samples were analyzed to assess vesicle structural integrity, drug retention and release kinetics after the injection. In this regard, data concerning size, size distribution, surface charge of vesicles and bilayer integrity and thickness, before and after the injections, were measured by dynamic light scattering experiments, cryo-electron microscopy, and X-ray scattering techniques. Finally, the effect of vesicle fast jet injection through the skin on drug release kinetics was checked by in vitro experiments. The retention of the morphological, physico-chemical, and technological features after injection, proved the integrity of vesicles after skin crossing as a high-speed liquid jet. The delivery of undamaged vesicular carriers beneath the skin is of utmost importance to create a controlled release drug depot in the hypoderm, which may be beneficial for several localized therapies. Overall results reported in this paper may broaden the range of application of liquid jet injectors to lipid vesicle based formulations thus combining beneficial performance of painless devices with those of liposomal drug delivery systems.

Design and syntheses of mono and multivalent mannosyl-lipoconjugates for targeted liposomal drug delivery

Multivalent mannosyl-lipoconjugates may be of interest for glycosylation of liposomes and targeted drug delivery because the mannose specifically binds to C-type lectin receptors on the particular cells. In this paper syntheses of two types of novel O-mannosides are presented. Conjugates 1 and 2 with a COOH- and NH2-functionalized spacer and the connection to a lysine and FmocNH-PEG-COOH, are described. The coupling reactions of prepared intermediates 6 and 4 with a PEGylated-DSPE or palmitic acid, respectively, are presented. Compounds 5, mono-, 8, di- and 12, tetravalent mannosyl-lipoconjugates, were synthesized. The synthesized compounds were incorporated into liposomes and liposomal preparations featuring exposed mannose units were characterized. Carbohydrate liposomal quartz crystal microbalance based assay has been established for studying carbohydrate⿿lectin binding. It was demonstrated that liposomes with incorporated mannosyl-lipoconjugates were effectively recognized by Con A and have great potential to be used for targeted liposomal drug delivery systems.

Liposomal drug delivery system

Lipid-based self-assembling vesicles were first described in 1961 and reported in 1964 by Dr. Alec D. Bangham (Bangham and Horne in J Mol Biol 8:660–668, 1964) at the Babraham Institute in Cambridge, UK, in which he wrote: “It is probable that at equilibrium each and every lipid bilayer forms an unbroken membrane-there being no exposed hydrocarbon/water interface-from which it follows that every aqueous compartment would be discrete and isolated from its neighbor, including a complete separation of the outermost compartment of the whole structure from the continuous phase in which it is suspended”. It is thermodynamically possible for each lipid bilayer to form a discrete membrane, separating the vesicle from the continuous aqueous phase in which it is suspended. These “unbroken membranes” were called as “liquid crystal” or “smectic mesophase”, “Bangasomes” after the name of Dr. Bangham, and finally “liposomes”. The word “liposome” derives from two Greek words of “lipo-meaning fat” and “soma-meaning body”. In the earlier days, these artificial vesicles (or liposomes) were used for the study of cell physiology such as ion (or drug) permeability, membrane fusion, membrane-bound enzyme properties or as a membrane model. More recently, much attention was brought to the uses of liposomes in medical fields as drug delivery systems and the first article of this kind was published in 1971 in FEBS Letters by Dr. George Gregoriadis and his co-workers, where amyloglucosidase and albumin were entrapped into liposome for the purpose of enzyme replacement therapy (Gregoriadis et al. in FEBS Lett 14(2):95–99, 1971). Since then, tremendous amounts of papers were published on the uses of liposomes as a drug delivery system (DDS). So, this mini-review is mainly focused on the use of liposome as DDS.

Photothermally Triggered Lipid Bilayer Phase Transition and Drug Release from Gold Nanorod and Indocyanine Green Encapsulated Liposomes.

In light-activated liposomal drug delivery systems (DDSs), the light sensitivity can be obtained by a photothermal agent that converts light energy into heat. Excess heat increases the drug permeability of the lipid bilayer, and drug is released as a result. In this work, two near-IR responsive photothermal agents in a model drug delivery system are studied: either gold nanorods (GNRs) encapsulated inside the liposomes or indocyanine green (ICG) embedded into the lipid bilayer. The liposome system is exposed to light, and the heating effect is studied with fluorescent thermometers: laurdan and CdSe quantum dots (QDs). Both photothermal agents are shown to convert light into heat in an extent to cause a phase transition in the surrounding lipid bilayer. This phase transition is also proven with laurdan generalized polarization (GP). In addition to the heating results, we show that the model drug (calcein) is released from the liposomal cavity with both photothermal agents when the light power is sufficient to cause a phase transition in the lipid bilayer.

Neuroprotection against cerebral ischemia/reperfusion injury by intravenous administration of liposomal fasudil

Fasudil, a Rho-kinase inhibitor, is a promising neuroprotectant against ischemic stroke; however, its low bioavailability is an obstacle to be overcome. Our previous study revealed that the liposomal drug delivery system is a hopeful strategy to increase the therapeutic efficacy of neuroprotectants. In the present study, the usefulness of intravenously administered liposomal fasudil for cerebral ischemia/reperfusion (I/R) injury treatment was examined in transient middle cerebral artery occlusion (t-MCAO) rats. The results showed that PEGylated liposomes of approximately 100nm in diameter accumulated more extensively in the I/R region compared with those of over 200nm. Confocal images showed that fluorescence-labeled liposomal fasudil was widely distributed in the I/R region, and was not noticeably taken up by microglia, which are well-known resident macrophages in the brain, and neuronal cells. These data indicated that liposomal fasudil mainly exerted its pharmacological activity by releasing fasudil from the liposomes in the I/R region. Moreover, liposomal fasudil effectively suppressed neutrophil invasion and brain cell damage in the t-MCAO rats, resulting in amelioration of their motor function deficits. These findings demonstrated both the importance of particle size for neuroprotectant delivery and the effectiveness of liposomal fasudil for the treatment of cerebral I/R injury.