Cyclodextrin-Mediated Drug Release from Liposomes Dispersed Within a Bioadhesive Gel

Bioavailability enhancement of voriconazole using liposomal pastilles: Formulation and experimental design investigation

Oral mucosa offers several advantages in the delivery of therapeutic molecules. It avoids presystemic metabolism, Nanoencapsulation techniques might be applied to conquer physical, chemical challenges and enhance drug penetration, formulation performance, prolonging drug residence time, and improving sensorial feeling. The present investigation is aimed to formulate liposomal pastilles with high bioavailability. Voriconazole Liposomes (VL) were produced by utilizing varied ratios of soya lecithin (SL) and cholesterol (CH) by solvent Injection method. RSM is utilized to identify the optimized formulation, as this design provides a thorough understanding of a process and also has great utilization in originating the robustness of the product. The main impact and interaction terms of the formulation variables were assessed quantitatively utilizing a mathematical-statistical approach indicating that both independent variables have significant ('P' value < 0.05) effects on particle size ('P' value: 0.0142), percentage entrapment efficiency ('P' value: 0.0120), percentage drug release through the dialysis membrane ('P' value: 0.0105), percentage drug release through porcine buccal mucosa ('P' value: 0.0171) and percentage zone of inhibition ('P' value: 0.0305). Optimal liposomal encapsulated in noticed in 15:10 lecithin: cholesterol concentration (VLP-6). Higher Lecithin and Cholesterol quantity in the liposome formulations resulted in lower drug entrapment efficiency and drug release when compared with middle levels of lecithin and cholesterol content formulation. The pastilles were prepared from the optimized liposomal formulation with a modified method reported in British Pharmaceutical Codex, 1907. These liposomal pastilles were subjected to evaluation of physicochemical parameters, In vitro drug release studies, stability studies, and In vivo bioavailability studies in comparison with pure voriconazole pastilles (PVP). The statistical data analysis results indicated that there was a significant difference in T_max, K_a, t_{1/2 abs}, t_{1/2 elim,} AUC_0-24, AUC_0-∞, AUMC_0-24 and AUMC_0-∞, values among PVP and VLP-6. There was no significant difference in C_max, K_el, MRT_0-24 and MRT_0-∞values among pure voriconazole pastilles and optimized liposomal formulation.

Aptamer-guided siRNA-loaded nanomedicines for systemic gene silencing in CD-44 expressing murine triple-negative breast cancer model

In this study, we describe a liposome-based siRNA delivery system with a core composed of siRNA:protamine complex and a shell designed for the active targeting of CD44-expressing cells using for the first time the anti-CD44 aptamer (named Apt1) as targeting ligand. Among all functions, CD44 is the most common cancer stem cell surface biomarker and is found overexpressed in many tumors making this an attractive receptor for therapeutic targeting. This unique non-cationic system was evaluated for the silencing of the reporter gene of luciferase (luc2) in a triple-negative breast cancer model in vitro and in vivo. We show the possibility of conjugating an aptamer to siRNA-containing liposomes for an efficient gene silencing in CD44-expressing tumor cells in vivo, in the perspective of silencing disease-related genes in tumors.

Supramolecular cyclodextrin-based drug nanocarriers

Supramolecular systems formed by the binding of several cyclodextrins (CDs) to polymers or lipids, either via non-covalent or covalent links, open a wide range of possibilities for the delivery of active substances. CDs can perform as multifunctionalizable cores to which very diverse (macro)molecules and drugs can be conjugated. Grafting with amphiphilic molecules can lead to nanoassemblies exhibiting a variety of architectures. CDs can also polymerize with other CDs or can be used to functionalize preexisting polymers to form polymers/networks with enhanced capability to form inclusion complexes. Alternatively, CDs can be exploited as transient cross-linkers to form poly(pseudo)rotaxane-based networks or zipper-like assemblies. Combination of mutifunctionality and complexation ability of CDs has been shown to be useful to develop depot-like formulations and colloidal nanocarriers with improved performances regarding easiness of administration, protection of the encapsulated substances, control of the delivery rate, and cell interactions. The aim of this review is to provide an overall view of the diversity of designs of CD-based supramolecular nanosystems with a special focus on the advances materialized in the last five years, including clinical trials.

Effect of liposomes on rheological and syringeability properties of hyaluronic acid hydrogels intended for local injection of drugs

The aim of this work was to thoroughly study the effect of liposomes on the rheological and the syringeability properties of hyaluronic acid (HA) hydrogels intended for the local administration of drugs by injection. Whatever the characteristics of the liposomes added (neutral, positively or negatively charged, with a corona of polyethylene glycol chains, size), the viscosity and the elasticity of HA gels increased in a lipid concentration-dependent manner. Indeed, liposomes strengthened the network formed by HA chains due to their interactions with this polymer. The nature and the resulting effects of these interactions depended on liposome composition and concentration. The highest viscosity and elasticity were observed with liposomes covered by polyethylene glycol chains while neutral liposomes displayed the lowest effect. Despite their high viscosity at rest, all the formulations remained easily injectable through needles commonly used for local injections thanks to the shear-thinning behavior of HA gels. The present study demonstrates that rheological and syringeability tests are both necessary to elucidate the behavior of such systems during and post injection. In conclusion, HA liposomal gels appear to be a promising and versatile formulation platform for a wide range of applications in local drug delivery when an injection is required.

Characterization and release studies of liposomal gels containing glutathione/cyclodextrins complexes potentially useful for cutaneous administration

The aim of this work is to develop and characterize a formulation intended for the cutaneous administration of glutathione (γ-glutamylcysteinylglycine, GSH), potentially useful for cellular defense against UV-induced damage. For this purpose, liposomes containing GSH or GSH/cyclodextrins(CDs) inclusion complexes as well as liposomes dispersed within a hydrophilic gel, were evaluated. These formulations were designed in order to obtain a system combining the advantages of liposomes as vehicles for topical drug delivery with those of CDs as penetration enhancers. The studied CDs were the natural (β-CD) and chemically modified (i.e., HP-β-CD and CH3 -β-CD) cyclodextrins. The prepared liposomes showed homogeneous size distribution, mean diameter in the range 622-1435 nm, small positive charge (+3.1 to +6.6 mV), and encapsulation efficiency of the peptide in the range 13.6%-23.7%. Release studies showed that the presence of the oligosaccharide may influence to some extent the amount of drug released, whereas stability studies clearly point out that the incorporation in a hydrophilic gel of 2-hydroxyethylcellulose insures a stable formulation maintaining unchanged the characteristics of liposomal vesicles.

A hybrid hydrogel biomaterial by nanogel engineering: bottom-up design with nanogel and liposome building blocks to develop a multidrug delivery system

New hybrid poly(ethylene glycol) (PEG) hydrogels crosslinked with both nanogels and nanogel-coated liposome complexes are obtained by Michael addition of the acryloyl group of a cholesterol-bearing pullulan (CHP) nanogel to the thiol group of pentaerythritol tetra(mercaptoethyl) polyoxyethylene. The nanogel-coated liposome complex is stably retained after gelation and the complexes are well dispersed in the hybrid gel. Microrheological measurements show that the strength and gelation time of the hybrid hydrogel can be controlled by changing the liposome:nanogel ratio. The hydrogel is gradually degraded by hydrolysis under physiological conditions. In this process, the nanogel is released first, followed by the nanogel-coated liposomes. Hybrid hydrogels that can incorporate various molecules into the nanogel and liposomes, and release them in a two-step controllable manner, represent a new functional scaffold capable of delivering multiple drugs, proteins or DNA.

ESR technique for noninvasive way to quantify cyclodextrins effect on cell membranes

A new way to study the action of cyclodextrin was developed to quantify the damage caused on cell membrane and lipid bilayer. The Electron Spin Resonance (ESR) spectroscopy was used to study the action of Randomly methylated-beta-cyclodextrin (Rameb) on living cells (HCT-116). The relative anisotropy observed in ESR spectrum of nitroxide spin probe (5-DSA and cholestane) is directly related to the rotational mobility of the probe, which can be further correlated with the microviscosity. The use of ESR probes clearly shows a close correlation between cholesterol contained in cells and cellular membrane microviscosity. This study also demonstrates the Rameb ability to extract cholesterol and phospholipids in time- and dose-dependent ways. In addition, ESR spectra enabled to establish that cholesterol is extracted from lipid rafts to form stable aggregates. The present work supports that ESR is an easy, reproducible and noninvasive technique to study the effect of cyclodextrins on cell membranes.

Complex hydrogel systems composed of polymers, liposomes, and cyclodextrins: implications of composition on rheological properties and aging

Rheological properties of complex hydrogels containing different amounts of liposomes and/or cyclodextrin (CD) were evaluated. Sonicated unilamellar vesicles (SUV) were loaded in a hydrogel composed of Carbopol 974 NF and hydroxyethylcellulose (Natrosol 250 HX). Phosphatidylcholine (PC) and hydrogenated-PC (HPC) liposomes, both mixed with cholesterol in a 2:1 lipid/chol mol ratio, were used. In some cases, hydroxypropyl-beta-cyclodextrin was also added (100 or 400 mg/mL). Gels were incubated at 40 degrees C/75% humidity for 7 days or 1 month to evaluate the effect of aging on their rheological properties. FTIR and DSC studies were performed to investigate possible interactions between the polymers and CD molecules at different CD concentrations. Static and dynamic rheological measurements were carried out. All gels had shear-thinning behavior (fitted well by the Cross model) with the exception of gels containing high concentrations of CD that were transformed into nonflowing elastic sticky solids, especially after aging. The more pronounced elastic behavior of gels containing 400 mg/mL CD is reflected by the higher values of relaxation strengths over all relaxation times. Complete interaction between polymers and CD, in the high-CD-content gels, as proven by FTIR and DSC studies, explains the dominating contribution of CD on gel characteristics. The addition of liposomes to such CD-containing gels has a substantial effect on their rheological properties, which are dependent on the liposome type (HPC/chol liposomes > PC/chol) and the lipid/CD ratio. This is explained by the "neutralization" of some CD molecules that prefer to interact with chol molecules that they extract from the lipid membranes. Gels with a high CD concentration (400 mg/mL) are almost insensitive to aging, whereas all other gels become slightly more elastic and less viscous as aging proceeds.

Physicochemical characterization of bioactive polyacrylic acid organogels as potential antimicrobial implants for the buccal cavity

This study describes the formulation and physicochemical characterization of poly(acrylic acid) (PAA) organogels, designed as bioactive implants for improved treatment of infectious diseases of the oral cavity. Organogels were formulated containing a range of concentrations of PAA (3-10% w/w) and metronidazole (2 or 5% w/w, representing a model antimicrobial agent) in different nonaqueous solvents, namely, glycerol (Gly), polyethylene glycol (PEG 400), or propylene glycol (PG). Characterization of the organogels was performed using flow rheometry, compressional analysis, oscillatory rheometry, in vitro mucoadhesion, moisture uptake, and drug release, methods that provide information pertaining to the nonclinical and clinical use of these systems. Increasing the concentration of PAA significantly increased the consistency, compressibility, storage modulus, loss modulus, dynamic viscosity, mucoadhesion, and the rate of drug release. These observations may be accredited to enhanced molecular polymer entanglement. In addition, the choice of solvent directly affected the physicochemical parameters of the organogels, with noticeable differences observed between the three solvents examined. These differences were accredited to the nature of the interaction of PAA with each solvent and, importantly, the density of the resultant physical cross-links. Good correlation was observed between the viscoelastic properties and drug release, with the exception of glycerol-based formulations containing 5 and 10% w/w PAA. This disparity was due to excessive swelling during the dissolution analysis. Ideally, formulations should exhibit controlled drug release, high viscoelasticity, and mucoadhesion, but should flow under minimal stresses. Based on these criteria, PEG 400-based organogels composed of 5% or 10% w/w PAA exhibited suitable physicochemical properties and are suggested to be a potentially interesting strategy for use as bioactive implants designed for use in the oral cavity.

Integrity of liposomes in presence of cyclodextrins: Effect of liposome type and lipid composition

Liposome stability during incubation in presence of cyclodextrins (CDs) is studied. Dried-rehydrated vesicle (DRV), multilamellar vesicle (MLV) and small unilamellar vesicle (SUV) calcein-encapsulating liposomes, composed of different lipids are formulated, and retention of calcein is followed during vesicle incubation in hydroxypropyl-beta-CD (HP beta-CD), HP gamma-CD or methyl-beta-CD (Me beta-CD), for 24h. Results demonstrate that liposome integrity in cyclodextrins is affected by lipid composition and type. For the same lipid composition calcein release from vesicles is faster in the order: MLV > DRV > SUV. Me beta-CD influences liposome stability most, compared to the other CD's studied. Vesicles composed of saturated phospholipids were found more stable compared to phosphatidyl-choline (PC) liposomes, suggesting that phospholipid saturation and membrane rigidity influences the interaction between liposomal-lipids and CD molecules. Chol (cholesterol) addition in lipid membrane improves PC-liposome integrity, but has opposite or no effect on liposomes consisting of saturated lipids. Decrease of vesicle dispersion turbidity and size distribution in presence of CD, implies that Me beta-CD induces vesicle disruption and solubilization (to micelles). Turbidity measurements confirm that DRV liposomes are affected more than SUV.

Study of the relationship between lipid binding properties of cyclodextrins and their effect on the integrity of liposomes

It is well known that cyclodextrins are able to extract lipids constituting membranes, increasing their fluidity and permeability. This behaviour towards biological membranes is directly linked to the toxicological effects of methylated cyclodextrins. However, confusion is currently made in the literature between the different methylated cyclodextrin derivatives. Moreover, a new methylated cyclodextrin derivative recently occurred in the market, the Crysmeb. We wanted to compare and understand the effect of the most currently used cyclodextrins on a model membrane. We studied the influence of natural cyclodextrins (betaCD and gammaCD), methylated derivatives (2,6-dimethyl-betaCD (Dimeb), 2,3,6-trimethyl-betaCD (Trimeb) and randomly methylated-betaCD (Rameb), as well as the new derivative Crysmeb), hydroxypropylated derivatives (HPbetaCD of different substitution degrees and HPgammaCD) and the sulfobutylated derivative (SBEbetaCD) on the release of a fluorescent marker encapsulated in the inner cavity of liposomes. It was shown that the observed effect on calcein release can be directly related to the affinity of cyclodextrins for both lipid components of liposomes, cholesterol and phosphatidylcholine. From this relationship, we were able to determine, for each cyclodextrin, a theoretical concentration giving rise to 50% or 100% calcein release. This theoretical concentration was confirmed experimentally. We have also showed that cyclodextrins which provoke calcein release also induce large structure modifications of liposomes.

Multivariate toxicity screening of liposomal formulations on a human buccal cell line

The influence of various formulation factors on the in vitro cellular toxicity of liposomes on human buccal cells (TR146), were studied by using the concept of statistical experimental design and multivariate evaluation. The factors investigated were the type of main phospholipid (egg-PC, DMPC, DPPC), lipid concentration, the type of charge, liposome size, and amount and nature of the charged component (diacyl-PA, diacyl-PG, diacyl-PS, stearylamine (SA), diacyl-TAP) in the liposomes. Both full factorial design and D-optimal designs were created. Several significant main factors and interactions were revealed. Positively charged liposomes were shown to be toxic. The toxicity of negatively charged liposomes was relatively low. Diacyl-TAP was less toxic than SA, and DPPC was less toxic than DMPC. Low level of positively charged component was favourable and essential when using egg-PC as the main lipid. The amount of negatively charged component, the liposome size, and the total lipid concentration did not affect the toxicity within the experimental room. DPPC appeared to be a good candidate when formulating both positively and negatively charged liposomes with low cellular toxicity. The concept of statistical experimental design and multivariate evaluation was shown to be a useful approach in cell toxicity screening studies.