Liposomal drug delivery systems: from concept to clinical applications

Harnessing photochemical internalization with dual degradable nanoparticles for combinatorial photo-chemotherapy

Light-controlled drug delivery systems constitute an appealing means to direct and confine drug release spatiotemporally at the site of interest with high specificity. However, the utilization of light-activatable systems is hampered by the lack of suitable drug carriers that respond sharply to visible light stimuli at clinically relevant wavelengths. Here, a new class of self-assembling, photo- and pH-degradable polymers of the polyacetal family is reported, which is combined with photochemical internalization to control the intracellular trafficking and release of anticancer compounds. The polymers are synthesized by simple and scalable chemistries and exhibit remarkably low photolysis rates at tunable wavelengths over a large range of the spectrum up to the visible and near infrared regime. The combinational pH and light mediated degradation facilitates increased therapeutic potency and specificity against model cancer cell lines in vitro. Increased cell death is achieved by the synergistic activity of nanoparticle-loaded anticancer compounds and reactive oxygen species accumulation in the cytosol by simultaneous activation of porphyrin molecules and particle photolysis.

Porphyrin-phospholipid liposomes permeabilized by near-infrared light

The delivery of therapeutic compounds to target tissues is a central challenge in treating disease. Externally controlled drug release systems hold potential to selectively enhance localized delivery. Here we describe liposomes doped with porphyrin–phospholipid that are permeabilized directly by near-infrared light. Molecular dynamics simulations identified a novel light-absorbing monomer esterified from clinically approved components predicted and experimentally demonstrated to give rise to a more stable porphyrin bilayer. Light-induced membrane permeabilization is enabled with liposomal inclusion of 10 molar % porphyrin–phospholipid and occurs in the absence of bulk or nanoscale heating. Liposomes reseal following laser exposure and permeability is modulated by varying porphyrin–phospholipid doping, irradiation intensity or irradiation duration. Porphyrin–phospholipid liposomes demonstrate spatial control of release of entrapped gentamicin and temporal control of release of entrapped fluorophores following intratumoral injection. Following systemic administration, laser irradiation enhances deposition of actively loaded doxorubicin in mouse xenografts, enabling an effective single-treatment antitumour therapy.

The delivery of therapeutics using an external trigger is an attractive route for the improvement of targeted disease treatment. Here, the authors have discovered a porphyrin–phospholipid liposome for light-controlled membrane permeabilization and use the system to deliver an anticancer drug in vivo.

Characterization and cytotoxicity studies on liposome-hydrophobic magnetite hybrid colloids

The aim of this study was to highlight the main features of magnetoliposomes prepared by TLE, using hydrophobic magnetite, and stabilized with oleic acid, instead of using the usual hydrophilic magnetite surrounded by sodium citrate. These biocompatible magnetoliposomes (MLs) were prepared with the purpose of producing a magnetic carrier capable of loading either hydrophilic or lipophilic drugs. The effect of different liposome/magnetite weight ratios on the stability of magnetoliposomes was evaluated by monitoring the mean diameter of the particles, their polydispersity index, and zeta potential over time. The prepared magnetoliposomes showed a high liposome-magnetite association, with magnetoliposomes containing PEG (polyethylene glycol) showing the best magnetite loading values. To verify the position of magnetite nanoparticles in the vesicular structures, the morphological characteristics of the structures were studied using transmission electron microscopy (TEM). TEM studies showed a strong affinity between hydrophobic magnetite nanoparticles, the surrounding oleic acid molecules, and phospholipids. Furthermore, the concentration above which one would expect to find a cytotoxic effect on cells as well as morphological cell-nanoparticle interactions was studied in situ by using the trypan blue dye exclusion assay, and the Prussian Blue modified staining method.

The Theranostic Path to Personalized Nanomedicine

Advances in nanotechnology and chemical engineering have led to the development of many different drug delivery systems. These 1-100(0) nm-sized carrier materials aim to increase drug concentrations at the pathological site, while avoiding their accumulation in healthy non-target tissues, thereby improving the balance between the efficacy and the toxicity of systemic (chemo-) therapeutic interventions. An important advantage of such nanocarrier materials is the ease of incorporating both diagnostic and therapeutic entities within a single formulation, enabling them to be used for theranostic purposes. We here describe the basic principles of using nanomaterials for targeting therapeutic and diagnostic agents to pathological sites, and we discuss how nanotheranostics and image-guided drug delivery can be used to personalize nanomedicine treatments.

Liposomal drug products and recent advances in the synthesis of supercritical fluid-mediated liposomes

Since the pioneering research of Bangham et al. in 1965, liposomes have attracted a large amount of interest as potential carriers of various bioactive molecules for clinical applications. However, scaling-up conventional methods of liposome preparation has been proven to be challenging. Compared with conventional methods, processes that use supercritical fluid (SCF)-CO2 require a reduced amount of organic solvent, are relatively fast and simple to perform, and yield stable and more uniform liposomes. A number of studies have demonstrated that SCF-CO2 methods might be suitable for industrial-scale manufacturing of liposomes. In this review there are two topics being discussed. We provide an overview of liposomal drug products and aim to describe the physicochemical properties of liposomes prepared using various SCF methods. We review all of the available literature on SCF-CO2-based liposomes and focus on the future applications of these innovative technologies in industrial-scale liposome preparation.

Characterizing EPR-mediated passive drug targeting using contrast-enhanced functional ultrasound imaging

The Enhanced Permeability and Retention (EPR) effect is extensively used in drug delivery research. Taking into account that EPR is a highly variable phenomenon, we have here set out to evaluate if contrast-enhanced functional ultrasound (ceUS) imaging can be employed to characterize EPR-mediated passive drug targeting to tumors. Using standard fluorescence molecular tomography (FMT) and two different protocols for hybrid computed tomography-fluorescence molecular tomography (CT-FMT), the tumor accumulation of a ~10 nm-sized near-infrared-fluorophore-labeled polymeric drug carrier (pHPMA-Dy750) was evaluated in CT26 tumor-bearing mice. In the same set of animals, two different ceUS techniques (2D MIOT and 3D B-mode imaging) were employed to assess tumor vascularization. Subsequently, the degree of tumor vascularization was correlated with the degree of EPR-mediated drug targeting. Depending on the optical imaging protocol used, the tumor accumulation of the polymeric drug carrier ranged from 5 to 12% of the injected dose. The degree of tumor vascularization, determined using ceUS, varied from 4 to 11%. For both hybrid CT-FMT protocols, a good correlation between the degree of tumor vascularization and the degree of tumor accumulation was observed, within the case of reconstructed CT-FMT, correlation coefficients of ~0.8 and p-values of <0.02. These findings indicate that ceUS can be used to characterize and predict EPR, and potentially also to pre-select patients likely to respond to passively tumor-targeted nanomedicine treatments.

Nano-enabled drug delivery: a research profile

Nano-enabled drug delivery (NEDD) systems are rapidly emerging as a key area for nanotechnology application. Understanding the status and developmental prospects of this area around the world is important to determine research priorities, and to evaluate and direct progress. Global research publication and patent databases provide a reservoir of information that can be tapped to provide intelligence for such needs. Here, we present a process to allow for extraction of NEDD-related information from these databases by involving topical experts. This process incorporates in-depth analysis of NEDD literature review papers to identify key subsystems and major topics. We then use these to structure global analysis of NEDD research topical trends and collaborative patterns, inform future innovation directions.

FROM THE CLINICAL EDITOR

This paper describes the process of how to derive nano-enabled drug delivery-related information from global research and patent databases in an effort to perform comprehensive global analysis of research trends and directions, along with collaborative patterns.

Liposomal delivery and polyethylene glycol-liposomal oxaliplatin for the treatment of colorectal cancer (Review)

Oxaliplatin is effective for the treatment of advanced colorectal cancer; however, its application is restricted due to its dose-limiting toxicity. Liposomes are sphere-shaped vesicles consisting of one or more phospholipid bilayers. Liposomes as drug carriers are characterized by delayed release, lesion targeting and may be used as a drug-delivery system to decrease the side effects of cytotoxic drugs. Active targeting modification of liposomes may change the biological distribution of the anticancer agents, reduce or reverse multidrug resistance of tumor cells and enhance the effects of anticancer therapy. Based on the characteristics mentioned above, the aim of the present review was to demonstrate that polyethylene glycol-liposomes containing oxaliplatin may offer advantages for the treatment of colorectal cancer in clinical practice.

Complexes between anionic liposomes and spherical polycationic brushes. An assembly of assemblies

This paper has at its objective the assembling of liposomal assemblies onto nanoparticles. In this manner, one generates nanoparticles with a high loading capacity. Thus, spherical spherical polycationic "brushes" (SPBs) were synthesized by graft polymerizing a cationic monomer, (trimethylammonium)ethylmethacrylate chloride, onto the surface of monodisperse polystyrene particles, ca. 100 nm in diameter. These particles were complexed with small unilamellar anionic liposomes, 40-60 nm in diameter, composed of egg lecithin (EL) and anionic phosphatidylserine (PS(1-)) in PS(1-)/EL ratios from 0.10 to 0.54, a key parameter designated as ν. These complexes were then characterized according to electrophoretic mobility, dynamic light scattering, conductivity, fluorescence, and cryogenic transmission electron microscopy, with the following main conclusions: (a) All added liposomes are totally associated with SPBs up to a certain saturation concentration (specific for each ν value). (b) The number of liposomes per SPB particle varies from 40 (ν = 0.1) to 14 (ν = 0.5). (c) At sufficiently high liposome concentrations, the SPBs experience an overall change from positive to negative charge. (d) SPB complexes tend to aggregate when their initial positive charge has been precisely neutralized by the anionic liposomes. Aggregation is impeded by either positive charge at lower lipid concentrations, or negative charge at higher lipid concentrations. (e) The liposomes remain intact (i.e., do not leak) when associated with SPBs, at ν ≤ 0.5. (f) Complete SPB/liposome dissociation occurs at external [NaCl] = 0.3 M for ν = 0.1 and at 0.6 M for ν = 0.5. Liposomes with ν = 0.54 do not dissociate from the SPBs even in NaCl solutions up to 1.0 M. (g) Complexation of the PS(1-)/EL liposomes to the SPBs induces flip-flop of PS(1-) from the inner leaflet to the outer leaflet. (h) The differences in the ability of PS(1-) (a cylindrical lipid) and CL(2-) (a conical lipid) to create membranes defects are attributed to geometric factors.

A porphodimethene chemical inhibitor of uroporphyrinogen decarboxylase

Uroporphyrinogen decarboxylase (UROD) catalyzes the conversion of uroporphyrinogen to coproporphyrinogen during heme biosynthesis. This enzyme was recently identified as a potential anticancer target; its inhibition leads to an increase in reactive oxygen species, likely mediated by the Fenton reaction, thereby decreasing cancer cell viability and working in cooperation with radiation and/or cisplatin. Because there is no known chemical UROD inhibitor suitable for use in translational studies, we aimed to design, synthesize, and characterize such a compound. Initial in silico-based design and docking analyses identified a potential porphyrin analogue that was subsequently synthesized. This species, a porphodimethene (named PI-16), was found to inhibit UROD in an enzymatic assay (IC50 = 9.9 µM), but did not affect porphobilinogen deaminase (at 62.5 µM), thereby exhibiting specificity. In cellular assays, PI-16 reduced the viability of FaDu and ME-180 cancer cells with half maximal effective concentrations of 22.7 µM and 26.9 µM, respectively, and only minimally affected normal oral epithelial (NOE) cells. PI-16 also combined effectively with radiation and cisplatin, with potent synergy being observed in the case of cisplatin in FaDu cells (Chou-Talalay combination index <1). This work presents the first known synthetic UROD inhibitor, and sets the foundation for the design, synthesis, and characterization of higher affinity and more effective UROD inhibitors.

Niosomes from 80s to present: the state of the art

Efficient and safe drug delivery has always been a challenge in medicine. The use of nanotechnology, such as the development of nanocarriers for drug delivery, has received great attention owing to the potential that nanocarriers can theoretically act as "magic bullets" and selectively target affected organs and cells while sparing normal tissues. During the last decades the formulation of surfactant vesicles, as a tool to improve drug delivery, brought an ever increasing interest among the scientists working in the area of drug delivery systems. Niosomes are self assembled vesicular nanocarriers obtained by hydration of synthetic surfactants and appropriate amounts of cholesterol or other amphiphilic molecules. Just like liposomes, niosomes can be unilamellar or multilamellar, are suitable as carriers of both hydrophilic and lipophilic drugs and are able to deliver drugs to the target site. Furthermore, niosomal vesicles, that are usually non-toxic, require less production costs and are stable over a longer period of time in different conditions, so overcoming some drawbacks of liposomes. The niosome properties are specifically dictated by size, shape, and surface chemistry which are able to modify the drug's intrinsic pharmacokinetics and eventual drug targeting to the areas of pathology. This up-to-date review deals with composition, preparation, characterization/evaluation, advantages, disadvantages and application of niosomes.

Synthetic studies on heterocyclic natural products

This paper highlights ongoing efforts toward Erythrina alkaloids, himandrine, tetrodotoxin, and thiopeptide antibiotics such as nosiheptide and describes representative spinoffs in biomedicine that emanated from the author’s research in synthetic organic chemistry.

"Single-single" amphiphilic janus dendrimers self-assemble into uniform dendrimersomes with predictable size

An accelerated modular synthesis of six libraries containing 29 amphiphilic Janus dendrimers, employed to discover and predict functions via primary structures, is reported. These dendrimers were constructed from a single hydrophobic and a single hydrophilic dendron, interconnected with l-Ala to form two constitutional isomeric libraries, with Gly to produce one library, and with l-propanediol ester to generate two additional constitutional isomeric libraries. They are denoted "single-single" amphiphilic Janus dendrimers. Assemblies obtained by injection of their ethanol solution into water were analyzed by dynamic light scattering and cryogenic transmission electron microscopy. A diversity of complex structures including soft and hard dendrimersomes, cubosomes, solid lamellae, and rod-like micelles were obtained in water. It was discovered that the "single-single" amphiphilic Janus dendrimers containing three triethylene glycol groups in the hydrophilic dendron favored the formation of dendrimersomes. Assemblies in bulk analyzed by differential scanning calorimetry and powder X-ray diffraction revealed that the amphiphilic Janus dendrimers with melting point or glass transition below room temperature self-assemble into soft dendrimersomes in water, while those with higher temperature transitions produce hard assemblies. In the range of concentrations where their size distribution is narrow, the diameter of the dendrimersomes is predictable by the d-spacing of their assemblies in bulk. These results suggested the synthesis of Library 6 containing two simpler constitutional isomeric benzyl ester based amphiphilic Janus dendrimers that self-assemble in water into soft dendrimersomes and multidendrimersome dendrimersomes with predictable dimensions.

Liposomal co-delivery of omacetaxine mepesuccinate and doxorubicin for synergistic potentiation of antitumor activity

PURPOSE

Anticancer chemotherapy usually involves the administration of several anticancer drugs that differ in their action mechanisms. Here, we aimed to test whether the combination of omacetaxine mepesuccinate (OMT) and doxorubicin (DOX) could show synergism, and whether the liposomal co-delivery of these two drugs could enhance their antitumor effects in cervical carcinoma model.

METHOD

OMT-loaded liposomes (OL) were prepared by loading the drug in the lipid bilayers. OL were then electrostatically complexed with DOX, yielding double-loaded liposomes (DOL). DOX-loaded liposomes (DL) were formulated by electrostatic interaction with negatively charged empty liposomes (EL). The combination index (CI) values were calculated to evaluate the synergism of two drugs. In vitro antitumor effects against HeLa cells were measured using CCK-8, calcein staining, and crystal violet staining. In vivo antitumor effects of various liposomes were tested using HeLa cell-bearing mice.

RESULTS

Combination of DOX and OMT had ratio-dependent synergistic activities, with very strong synergism observed at a molar ratio of 4:1 (DOX:OMT). The sizes of EL, DL, OL, and DOL did not significantly differ, but the zeta potentials of DL and DOL were slightly higher than those of OL and EL. In vitro, DOL showed higher antitumor activity than OL, DL or EL in cervical carcinoma HeLa cells. In vivo, unlike other liposomes, DOL reduced the tumor growths by 98.6% and 97.3% relative to the untreated control on day 15 and 25 after the cessation of treatment, respectively.

CONCLUSIONS

These results suggest that liposomal co-delivery of DOX and OMT could synergistically potentiate antitumor effects.

Targeting of BRAF resistant melanoma via extracellular matrix metalloproteinase inducer receptor

BACKGROUND

The BRAF inhibitor vemurafenib (PLX) has shown promise in treating metastatic melanoma, but most patients develop resistance to treatment after 6 mo. We identified a transmembrane protein, extracellular matrix metalloproteinase inducer (EMMPRIN) as a cell surface receptor highly expressed by PLX-resistant melanoma. Using an S100A9 ligand, we created an EMMPRIN targeted probe and liposome that binds to melanoma cells in vivo, thus designing a novel drug delivery vehicle.

METHODS

PLX-resistant cells were established through continuous treatment with PLX-4032 over the course of 1 y. Both PLX-resistant and sensitive melanoma cell lines were evaluated for the expression of unique cell surface proteins, which identified EMMPRIN as an overexpressed protein in PLX0-resistant cells and S100A9 is a ligand for EMMPRIN. To design a probe for EMMPRIN, S100A9 ligand was conjugated to a CF-750 near-infrared (NIR) dye. EMMPRIN targeted liposomes were created to encapsulate CF-750 NIR dye. Liposomes were characterized by scanning electron microscopy, flow cytometry, and in vivo analysis. A2058PLX and A2058 cells were subcutaneously injected into athymic mice. S100A9 liposomes were intravenously injected and tumor accumulation was evaluated using NIR fluorescent imaging.

RESULTS

Western blot and flow cytometry demonstrated that PLX sensitive and resistant A2058 and A375 melanoma cells highly express EMMPRIN. S100A9 liposomes were 200 nm diameter and uniformly sized. Flow cytometry demonstrated 100X more intracellular dye uptake by A2058 cells treated with S100A9 liposomes compared with untargeted liposomes. In vivo accumulation of S100A9 liposomes within subcutaneous A2058 and A2058PLX tumors was observed from 6-48 h, with A2058PLX accumulating significantly higher levels (P = 0.001626).

CONCLUSIONS

EMMPRIN-targeted liposomes via an S100A9 ligand are a novel, targeted delivery system which could provide improved EMMPRIN specific drug delivery to a tumor.

In vitro interaction of polyelectrolyte nanocapsules with model cells

The nanocapsules based on a liquid core with polyelectrolyte shells prepared by the technique of sequential adsorption of polyelectrolytes (LbL) were investigated to verify capsules bioacceptance. Using AOT (docusate sodium salt) as emulsifier, we obtained liquid cores, stabilized by the interfacial complex AOT/PLL (poly-l-lysine hydrobromide). These liquid cores were encapsulated by sequential adsorption of polyelectrolytes using biocompatible polyanion PGA (poly-l-glutamic acid sodium salt) and biocompatible polycation PLL. The average size of the formed capsules was 60-80 nm. The influence of a number of polyelectrolytes layer in the shell (thickness of polyelectrolytes shell), surface charge, and capsule doses on cell viability was studied in a cellular coculture assay. In order to improve nanocapsules biocompatibility, the PEG-ylated external layers were prepared using PGA-g-PEG (PGA grafted by PEG poly(ethylene glycol)). For the most toxic nanocapsules (with only one polycation layer) about 90% of cells could survive when the concentration of nanocapsules was below 0.2 × 10(6) per one cell. That suggests that they use as a delivery vehicles is quite safe for living cells. Analysis of internalization of AOT(PLL/PGA)4-g-PEG in HEK 293 cells indicates that tested nanocapsules can easily penetrate cells membrane.

Pharmacokinetics, tumor accumulation and antitumor activity of nanoliposomal irinotecan following systemic treatment of intracranial tumors

AIM

We sought to evaluate nanoliposomal irinotecan as an intravenous treatment in an orthotopic brain tumor model.

MATERIALS & METHODS

Nanoliposomal irinotecan was administered intravenously in the intracranial U87MG brain tumor model in mice, and irinotecan and SN-38 levels were analyzed in malignant and normal tissues. Therapy studies were performed in comparison to free irinotecan and control treatments.

RESULTS

Tissue analysis demonstrated favorable properties for nanoliposomal irinotecan, including a 10.9-fold increase in tumor AUC for drug compared with free irinotecan and 35-fold selectivity for tumor versus normal tissue exposure. As a therapy for orthotopic brain tumors, nanoliposomal irinotecan showed a mean survival time of 54.2 versus 29.5 days for free irinotecan. A total of 33% of the animals receiving nanoliposomal irinotecan showed no residual tumor by study end compared with no survivors in the other groups.

CONCLUSION

Nanoliposomal irinotecan administered systemically provides significant pharmacologic advantages and may be an efficacious therapy for brain tumors.

Application of liposomes in treatment of rheumatoid arthritis: quo vadis

The most common treatments for rheumatoid arthritis include nonsteroidal anti-inflammatory drugs (NSAIDs), corticosteroids, disease modifying antirheumatic drugs (DMARDs), and some biological agents. However, none of the treatments available is able to achieve the ultimate goal of treatment, that is, drug-free remission. This limitation has shifted the focus of treatment to delivery strategies with an ability to deliver the drugs into the synovial cavity in the proper dosage while mitigating side effects to other tissues. A number of approaches like microemulsions, microspheres, liposomes, microballoons, cocrystals, nanoemulsions, dendrimers, microsponges, and so forth, have been used for intrasynovial delivery of these drugs. Amongst these, liposomes have proven to be very effective for retaining the drug in the synovial cavity by virtue of their size and chemical composition. The fast clearance of intra-synovially administered drugs can be overcome by use of liposomes leading to increased uptake of drugs by the target synovial cells, which in turn reduces the exposure of nontarget sites and eliminates most of the undesirable effects associated with therapy. This review focuses on the use of liposomes in treatment of rheumatoid arthritis and summarizes data relating to the liposome formulations of various drugs. It also discusses emerging trends of this promising technology.

Effective interaction between small unilamellar vesicles as probed by coarse-grained molecular dynamics simulations

A series of molecular dynamics (MD) simulations has been undertaken to investigate the effective interaction between vesicles including PC (phosphatidylcholine) and PE (phosphatidylethanolamine) lipids using the Shinoda–DeVane–Klein coarse-grained force field. No signatures of fusion were detected during MD simulations employing two apposed unilamellar vesicles, each composed of 1512 lipid molecules. Association free energy of the two stable vesicles depends on the lipid composition. The two PC vesicles exhibit a purely repulsive interaction with each other, whereas two PE vesicles show a free energy gain at the contact. A mixed PC/PE (1:1) vesicle shows a higher flexibility having a lower energy barrier on the deformation, which is caused by lipid sorting within each leaflet of the membranes. With a preformed channel or stalk between proximal membranes, PE molecules contribute to stabilize the stalk. The results suggest that the lipid components forming the membrane with a negative spontaneous curvature contribute to stabilize the stalk between two vesicles in contact.

Guiding principles in the design of ligand-targeted nanomedicines

Medicines for the treatment of most human pathologies are encumbered by unwanted side effects that arise from the deposition of an effective drug into the wrong tissues. The logical remedy for these undesirable properties involves selective targeting of the therapeutic agent to pathologic cells, thereby avoiding collateral toxicity to healthy cells. Since significant advantages can also accrue by incorporating a therapeutic or imaging agent into a nanoparticle, many laboratories are now combining both benefits into a single formulation. This review will focus on the major guiding principles in the design of ligand-targeted nanoparticles, including optimization of their chemical and physical properties, selection of the ideal targeting ligand, engineering of the appropriate surface passivation and linker strategies to achieve selective delivery of the entrapped cargo to the desired diseased cell.

Comparison of in vitro dialysis release methods of loperamide-encapsulated liposomal gel for topical drug delivery

Background

The purpose of this study was to determine the most appropriate dialysis equilibrium method to assess liposomal gel formulations containing hydrophobic drugs, to give the most accurate indication of drug release.

Methods

Loperamide hydrochloride-encapsulated liposomes, composed of L-α-phosphatidylcholine and cholesterol (molar ratio of 2:1), were prepared according to the method of dried lipid film hydration. The liposomes were incorporated into a carbopol gel (0.5%, weight/weight). The release of the drug from the nanoparticles was assessed using a number of variations of the dialysis technique, taking into account solubility parameters and formulation. Method 1 (below saturation point) and Method 2 (above saturation point) used a dilution method to evaluate how drug concentration and solubility affects the in vitro drug-release profile of loperamide hydrochloride, while Methods 3 (below saturation point) and 4 (above saturation point) evaluated how drug concentration and the gel base affect the release profile.

Results

In Method 1, the liposomes showed a rapid release of just over 60% in the first 3 hours and then a slower, sustained release to just over 70% at 24 hours. Method 2 showed a gradual, sustained release profile with the liposomes with 55% release at 24 hours. In Method 3, the liposomes showed a rapid burst release of 98% at 2 hours. In Method 4, the liposomal gel had a rapid release of 60% within 3 hours and then a more gradual, sustained release with 86% release at 24 hours. The free drug suspension in Methods 2 and 4 showed a limited release across the dialysis membrane, in comparison to Methods 1 and 3, which showed a complete release in a timely manner.

Conclusion

This study has demonstrated that the actual method used for equilibrium dialysis plays a significant role in determining the true characteristics of a topical nanoformulation, with Method 3 providing the most accurate indication of the release of a hydrophobic drug from a topical liposomal formulation.

Liposomal co-delivery of daptomycin and clarithromycin at an optimized ratio for treatment of methicillin-resistant Staphylococcus aureus infection

CONTEXT

Pathogen evolution currently outpaces novel drug development, and because development of new antibiotics is pending, combination therapy with existing drugs may provide effective alternative treatments.

OBJECTIVE

The present study was aimed at evaluating the concurrent use of two antibiotics, daptomycin and clarithromycin, against methicillin-resistant Staphylococcus aureus (MRSA) infections.

MATERIALS AND METHODS

Polyeythylene glycol (PEGylated liposomes loaded with daptomycin, clarithromycin, or both (PL[CD]) at an optimized mass ratio of 1:32 were generated and characterized using dynamic light scattering and electron microscopy. In vitro and in vivo approaches were used to compare liposome effects on MRSA.

RESULTS

PL[CD] were stable, with a mean (± SD) vesicle diameter of 98.2 ± 2.21 nm and encapsulation efficiency of 94.71 ± 1.37% (daptomycin) and 92.94 ± 1.21% (clarithromycin). Compared with daptomycin-only liposomes, PL[CD] showed significantly enhanced anti-MRSA activity in vitro and significantly reduced MRSA bacterial load and increased host survival in vivo.

DISCUSSION

Co-delivery of daptomycin with clarithromycin produced significant anti-MRSA activity in the presence of only one-thirtieth of the concentration required in liposomes containing daptomycin only.

CONCLUSION

These findings suggested that concurrent liposomal delivery of daptomycin and clarithromycin has the potential to be an effective and less toxic treatment for MRSA infections.

Sustained drug release in nanomedicine: a long-acting nanocarrier-based formulation for glaucoma

Therapeutic nanomedicine has concentrated mostly on anticancer therapy by making use of the nanosize for targeted therapy. Such nanocarriers are not expected to have sustained release of the bioactive molecule beyond a few days. There are other conditions where patients can benefit from sustained duration of action following a single instillation, but achieving this has been difficult in nanosized carriers. An important prerequisite for sustained delivery over several months is to have sufficiently high drug loading, without disruption or changes to the shape of the nanocarriers. Here we report on successful development of a drug-encapsulated nanocarrier for reducing intraocular pressure in a diseased nonhuman primate model and explain why it has been possible to achieve sustained action in vivo. The drug is a prostaglandin derivative, latanoprost, while the carrier is a nanosized unilamellar vesicle. The mechanistic details of this unique drug-nanocarrier combination were elucidated by isothermal titration calorimetry. We show, using Cryo-TEM and dynamic light scattering, that the spherical shape of the liposomes is conserved even at the highest loading of latanoprost and that specific molecular interactions between the drug and the lipid are the reasons behind improved stability and sustained release. The in vivo results clearly attest to sustained efficacy of lowering the intraocular pressure for 120 days, making this an excellent candidate to be the first truly sustained-release nanomedicine product. The mechanistic details we have uncovered should enable development of similar systems for other conditions where sustained release from nanocarriers is desired.

Nano-engineered erythrocyte ghosts as inhalational carriers for delivery of fasudil: preparation and characterization

PURPOSE

Nanoerythrosomes (NERs), an engineered derivative of erythrocytes, have long been used as drug delivery carriers. These cell based carriers are biocompatible and biodegradable, and they exhibit efficient drug loading, targeting specificity and prolonged biological half-life. In this study, we have evaluated the feasibility of NERs as inhalable carriers for delivery of fasudil, an investigational drug for the treatment of pulmonary arterial hypertension.

METHODS

We prepared NERs by hypotonic lysis of erythrocytes derived from rat blood followed by extrusion through polycarbonate membranes. The formulations were optimized and characterized for size, morphology, entrapment efficiency, stability, cellular uptake and in-vitro release profiles followed by monitoring of drug absorption and safety evaluation after intratracheal administration of fasudil-loaded NERs into rats.

RESULTS

NERs were spherical in shape with an average size of 154.1 ± 1.31 nm and the drug loading efficiency was 48.76 ± 2.18%. Formulations were stable when stored at 4°C for 3 weeks. When incubated with rat pulmonary arterial smooth muscle cells (PASM), a significant amount of NERs was taken up by PASM cells. The drug encapsulated in NERs inhibited the rho-kinase activity upto 50%, which was comparable with the plain fasudil. A ~6-8 fold increase in the half-life of fasudil was observed when encapsulated in NERs.

CONCLUSION

This study suggests that nanoerythrosomes can be used as cell derived carriers for inhalational delivery of fasudil.

Targeted liposomal drug delivery systems for the treatment of B cell malignancies

Nanoparticulate systems have demonstrated significant potential for overcoming the limitations of non-specific adverse effects related to chemotherapy. The treatment of blood malignancies employing targeted particulate drug delivery systems presents unique challenges and considerable research has been focused towards the development of targeted liposomal formulations for B cell malignancies. These formulations are aimed at achieving selectivity towards the malignant cells by targeting several cell surface markers which are over-expressed in that specific malignancy. CD19, CD20, CD22 and CD74 are few of such markers of which CD19, CD22 and CD74 are internalizing and CD20 is non-internalizing. Systems which have been developed to target both types of these cell surface markers are discussed. Specifically, the efficacy and development of targeted liposomes is considered. A number of studies have demonstrated the advantages of targeted liposomal systems encapsulating doxorubicin or vincristine. However, liposomal encapsulation of newer anti-neoplastic agents such as AD 198 which are superior to doxorubicin should be considered.

Ultrasound-mediated destruction of LHRHa-targeted and paclitaxel-loaded lipid microbubbles induces proliferation inhibition and apoptosis in ovarian cancer cells

Although paclitaxel (PTX) is used with platinum as the first line chemotherapy regimen for ovarian cancer, its clinical efficacy is often limited by severe adverse effects. Ultrasound-targeted microbubble destruction (UTMD) technique holds a great promise in minimizing the side effects and maximizing the therapeutic efficacy. However, the technique typically uses nontargeted microbubbles with suboptimal efficiency. We synthesized targeted and PTX-loaded microbubbles (MBs) for UTMD mediated chemotherapy in ovarian cancer cells. PTX-loaded lipid MBs were coated with a luteinizing hormone-releasing hormone analogue (LHRHa) through a biotin-avidin linkage to target the ovarian cancer A2780/DDP cells that express the LHRH receptor. In the cell culture studies, PTX-loaded and LHRHa-targeted MBs (TPLMBs) in combination with ultrasound (300 kHz, 0.5 W/cm(2), 30 s) demonstrated antiproliferative activities of 41.30 ± 3.93%, 67.76 ± 2.45%, and 75.93 ± 2.81% at 24, 48, and 72 h after the treatment, respectively. The cell apoptosis ratio at 24 h after the treatment is 32.6 ± 0.79%, which is significantly higher than other treatment groups such as PTX only and no-targeted PTX-loaded MBs (NPLMBs) with or without ultrasound mediation. Our experiment verifies the hypothesis that ultrasound mediation of ovarian cancer-targeted and drug-loaded MBs will enhance the PTX therapeutic efficiency.

Photostability of barnidipine in combined cyclodextrin-in-liposome matrices

Background: The improvement of barnidipine photostability was investigated in cyclodextrin or liposome matrices and in appropriate combinations of these matrices. These supramolecular systems allowed the preparation of liquid formulations, as an alternative to the current solid commercial specialties. Materials & methods: Photodegradation stressing tests were performed according to the ICH rules and monitored by derivative spectrophotometry. Optimization was evaluated in terms of drug-inclusion efficiency. Results: The photodegradation rate of barnidipine in ethanol proved rapid (residual percentage of 29.81%) after a radiation exposure of 225 kJ/m2. The residual concentrations detected for liposome and cyclodextrin complexes were 42.90 and 72.03%, respectively. The best results were obtained when the drug–cyclodextrin complex was in turn entrapped in liposomes (residual percentage of 90.78%). Conclusion: The stability of the drug-in-cyclodextrin-in-liposome system increased significantly with a value close to that of solid formulations whose residual percentage was 96.03%.

Free and copolymerized γ-cyclodextrins regulate the performance of dexamethasone-loaded dextran microspheres for bone regeneration

Incorporation of γ-cyclodextrins (γ-CD), as free entities or structural monomers (acrylamidomethyl-γ-cyclodextrin, γ-CD–NMA), into dextran-methacrylate (dextran-MA) photopolymerized spheres modifies the loading and release of an osteogenic agent.

Emerging research and clinical development trends of liposome and lipid nanoparticle drug delivery systems

Liposomes are spherical-enclosed membrane vesicles mainly constructed with lipids. Lipid nanoparticles are loaded with therapeutics and may not contain an enclosed bilayer. The majority of those clinically approved have diameters of 50-300 nm. The growing interest in nanomedicine has fueled lipid-drug and lipid-protein studies, which provide a foundation for developing lipid particles that improve drug potency and reduce off-target effects. Integrating advances in lipid membrane research has enabled therapeutic development. At present, about 600 clinical trials involve lipid particle drug delivery systems. Greater understanding of pharmacokinetics, biodistribution, and disposition of lipid-drug particles facilitated particle surface hydration technology (with polyethylene glycol) to reduce rapid clearance and provide sufficient blood circulation time for drug to reach target tissues and cells. Surface hydration enabled the liposome-encapsulated cancer drug doxorubicin (Doxil) to gain clinical approval in 1995. Fifteen lipidic therapeutics are now clinically approved. Although much research involves attaching lipid particles to ligands selective for occult cells and tissues, preparation procedures are often complex and pose scale-up challenges. With emerging knowledge in drug target and lipid-drug distribution in the body, a systems approach that integrates knowledge to design and scale lipid-drug particles may further advance translation of these systems to improve therapeutic safety and efficacy.

Lumazine synthase protein cage nanoparticles as modular delivery platforms for targeted drug delivery

Lumazine synthase protein cage nanoparticle is developed as a modular delivery nanoplatform that delivers drugs to their target cancer cells.

Photodegradable poly(ester amide)s for indirect light-triggered release of paclitaxel

A photodegradable poly(ester amide) was developed. An amphiphilic graft copolymer derivative with paclitaxel conjugated via ester linkages formed micelles that released paclitaxel in response to UV light.

A molecular level understanding of interaction between FTY720 (Fingolimod hydrochloride) and DMPC multilamellar vesicles

This work focuses on the molecular level understanding of interaction between FTY720 (Fingolimod hydrochloride) and dimyristoylphosphatidylcholine (DMPC) multilamellar vesicles (MLVs) as a drug molecule carrier by investigating the structural changes, solubilisation effect and thermotropic phase behaviour.

Magnetoliposomes: opportunities and challenges

Combining liposomes with magnetic nanoparticles is an intriguing approach to create multifunctional vesicles for medical applications, which range from controlled drug delivery vehicles to diagnostic imaging enhancers. Over the past decade, significant effort has been invested in developing such hybrids – widely known as magnetoliposomes – and has led to numerous new concepts. This review provides an overview on of the current state of the art in this field. The concept of magnetic fluid hyperthermia and stimuli-responsive nanoparticles for drug delivery is briefly recapitulated. The materials needed for these hybrids are addressed as well. The three typically followed approaches to associate magnetic nanoparticles to the liposomes are described and discussed more in detail. The final chapters are dedicated to the analytical methods used to characterize these hybrids and to theoretical considerations relevant for bilayer-embedded nanoparticles.

Nanotechnology for in vivo targeted siRNA delivery

Small interfering RNAs (siRNAs) can specifically inhibit gene expression. As a result, they have tremendous scientific and clinical potential. However, the use of these molecules in patients and animal models has been limited by challenges with delivery. Intracellular RNA delivery is difficult; it requires a system that protects the siRNA from degradative nucleases in the bloodstream, minimizes clearance by the reticuloendothelial system, maximizes delivery to the target tissue, and promotes entry into, and out of, an endocytic vesicle. Despite these barriers, recent data suggest that RNA may be targeted to cells of interest in vivo. Herein we outline strategies for targeted siRNA delivery, and describe how these strategies may be improved.

Enhanced localization of anticancer drug in tumor tissue using polyethylenimine-conjugated cationic liposomes

Liposome-based drug delivery systems hold great potential for cancer therapy. However, to enhance the localization of payloads, an efficient method of systemic delivery of liposomes to tumor tissues is required. In this study, we developed cationic liposomes composed of polyethylenimine (PEI)-conjugated distearoylglycerophosphoethanolamine (DSPE) as an enhanced local drug delivery system. The particle size of DSPE-PEI liposomes was 130 ± 10 nm and the zeta potential of liposomes was increased from -25 to 30 mV by the incorporation of cationic PEI onto the liposomal membrane. Intracellular uptake of DSPE-PEI liposomes by tumor cells was 14-fold higher than that of DSPE liposomes. After intratumoral injection of liposomes into tumor-bearing mice, DSPE-PEI liposomes showed higher and sustained localization in tumor tissue compared to DSPE liposomes. Taken together, our findings suggest that DSPE-PEI liposomes have the potential to be used as effective drug carriers for enhanced intracellular uptake and localization of anticancer drugs in tumor tissue through intratumoral injection.

Liposome-like Nanostructures for Drug Delivery

Liposomes are a class of well-established drug carriers that have found numerous therapeutic applications. The success of liposomes, together with recent advancements in nanotechnology, has motivated the development of various novel liposome-like nanostructures with improved drug delivery performance. These nanostructures can be categorized into five major varieties, namely: (1) polymer-stabilized liposomes, (2) nanoparticle-stabilized liposomes, (3) core-shell lipid-polymer hybrid nanoparticles, (4) natural membrane-derived vesicles, and (5) natural membrane coated nanoparticles. They have received significant attention and have become popular drug delivery platforms. Herein, we discuss the unique strengths of these liposome-like platforms in drug delivery, with a particular emphasis on how liposome-inspired novel designs have led to improved therapeutic efficacy, and review recent progress made by each platform in advancing healthcare.

Phototriggerable liposomes: current research and future perspectives

The field of cancer nanomedicine is considered a promising area for improved delivery of bioactive molecules including drugs, pharmaceutical agents and nucleic acids. Among these, drug delivery technology has made discernible progress in recent years and the areas that warrant further focus and consideration towards technological developments have also been recognized. Development of viable methods for on-demand spatial and temporal release of entrapped drugs from the nanocarriers is an arena that is likely to enhance the clinical suitability of drug-loaded nanocarriers. One such approach, which utilizes light as the external stimulus to disrupt and/or destabilize drug-loaded nanoparticles, will be the discussion platform of this article. Although several phototriggerable nanocarriers are currently under development, I will limit this review to the phototriggerable liposomes that have demonstrated promise in the cell culture systems at least (but not the last). The topics covered in this review include (i) a brief summary of various phototriggerable nanocarriers; (ii) an overview of the application of liposomes to deliver payload of photosensitizers and associated technologies; (iii) the design considerations of photoactivable lipid molecules and the chemical considerations and mechanisms of phototriggering of liposomal lipids; (iv) limitations and future directions for in vivo, clinically viable triggered drug delivery approaches and potential novel photoactivation strategies will be discussed.

Influence of Polyethylene Glycol Lipid Desorption Rates on Pharmacokinetics and Pharmacodynamics of siRNA Lipid Nanoparticles

Lipid nanoparticles (LNPs) encapsulating short interfering RNAs that target hepatic genes are advancing through clinical trials, and early results indicate the excellent gene silencing observed in rodents and nonhuman primates also translates to humans. This success has motivated research to identify ways to further advance this delivery platform. Here, we characterize the polyethylene glycol lipid (PEG-lipid) components, which are required to control the self-assembly process during formation of lipid particles, but can negatively affect delivery to hepatocytes and hepatic gene silencing in vivo. The rate of transfer from LNPs to plasma lipoproteins in vivo is measured for three PEG-lipids with dialkyl chains 14, 16, and 18 carbons long. We show that 1.5 mol % PEG-lipid represents a threshold concentration at which the chain length exerts a minimal effect on hepatic gene silencing but can still modify LNPs pharmacokinetics and biodistribution. Increasing the concentration to 2.5 and 3.5 mol % substantially compromises hepatocyte gene knockdown for PEG-lipids with distearyl (C18) chains but has little impact for shorter dimyristyl (C14) chains. These data are discussed with respect to RNA delivery and the different rates at which the steric barrier disassociates from LNPs in vivo.Molecular Therapy-Nucleic Acids (2013) 2, e139; doi:10.1038/mtna.2013.66; published online 17 December 2013.