Željka Vanić

Chitosan-coated liposomes for topical vaginal therapy: Assuring localized drug effect

The choice of drug therapy in pregnant patients suffering from vaginal infections is limited by the safety profile of the drug. Assuring the efficient topical therapy to avoid systemic absorption is considered the best therapy option. Chitosan-coated liposomes have been developed and optimized to assure localized therapy of clotrimazole. Chitosan was selected as mucoadhesive polymer both to prolong systems retention at the vaginal site and act on biofilms responsible for high recurrence of infections. Sonicated liposomes were coated with chitosan in three different concentrations, namely 0.1, 0.3 and 0.6% (w/v). Clotrimazole-containing (22 μg/mg lipid) chitosan-coated liposomes were in the size range of 100-200 nm. The in vitro release studies confirmed prolonged release of clotrimazole from both non-coated and chitosan-coated liposomes as compared to control. The ex vivo penetration experiments performed on the pregnant sheep vaginal tissue showed that coated liposomes assured increased clotrimazole tissue retention and reduced its penetration as compared to the control. Mucin studies revealed that the coating with lower chitosan concentration increased the systems mucoadhesive potential, as compared to coating with higher concentrations. These results provide a good platform for further in vivo animal studies on mucoadhesive liposomes destined to localized vaginal therapy.

In vitro skin models as a tool in optimization of drug formulation

(Trans)dermal drug therapy is gaining increasing importance in the modern drug development. To fully utilize the potential of this route, it is important to optimize the delivery of active ingredient/drug into/through the skin. The optimal carrier/vehicle can enhance the desired outcome of the therapy therefore the optimization of skin formulations is often included in the early stages of the product development. A rational approach in designing and optimizing skin formulations requires well-defined skin models, able to identify and evaluate the intrinsic properties of the formulation. Most of the current optimization relies on the use of suitable ex vivo animal/human models. However, increasing restrictions in use and handling of animals and human skin stimulated the search for suitable artificial skin models. This review attempts to provide an unbiased overview of the most commonly used models, with emphasis on their limitations and advantages. The choice of the most applicable in vitro model for the particular purpose should be based on the interplay between the availability, easiness of the use, cost and the respective limitations.

Novel vaginal drug delivery system: deformable propylene glycol liposomes-in-hydrogel

Abstract Deformable propylene glycol-containing liposomes (DPGLs) incorporating metronidazole or clotrimazole were prepared and evaluated as an efficient drug delivery system to improve the treatment of vaginal microbial infections. The liposome formulations were optimized based on sufficient trapping efficiencies for both drugs and membrane elasticity as a prerequisite for successful permeability and therapy. An appropriate viscosity for vaginal administration was achieved by incorporating the liposomes into Carbopol hydrogel. DPGLs were able to penetrate through the hydrogel network more rapidly than conventional liposomes. In vitro studies of drug release from the liposomal hydrogel under conditions simulating human treatment confirmed sustained and diffusion-based drug release. Characterization of the rheological and textural properties of the DPGL-containing liposomal hydrogels demonstrated that the incorporation of DPGLs alone had no significant influence on mechanical properties of hydrogels compared to controls. These results support the great potential of DPGL-in-hydrogel as an efficient delivery system for the controlled and sustained release of antimicrobial drugs in the vagina.

Characterization of various deformable liposomes with metronidazole.

Objective: The aim of this study was to investigate various deformable liposomes for their potential application for the vaginal administration of metronidazole. Materials and methods: Deformable liposomes composed of egg phosphatidylcholine (EPC) and various surfactants [sodium deoxycholate (SDCh), Tween 80 or Span 80] and conventional liposomes consisting of EPC and egg phosphatidylglycerol-sodium (EPG-Na) were prepared with and without metronidazole. Additionally, a freeze-thaw method was applied to both classes of vesicles (liposomes) containing the drug to improve its trapping capacity. All of the liposomes prepared were characterized and compared in terms of size, polydispersity, zeta potential, entrapment efficiency and their permeability on a Caco-2 cell monolayer. Results and discussion: Conventional liposomes, both with and without metronidazole, were larger than the deformable vesicles. The presence of ethanol in the preparations of the elastic EPC/SDCh and EPC/Tween 80 liposomes was found to affect the particle size in terms of reducing this parameter. Different types of vesicles were compared for their trapping efficiency of metronidazole and the highest entrapment was observed with conventional liposomes. However, deformable EPC/SDCh liposomes were found to enhance the permeability of metronidazole more effectively than the conventional liposomes based on the in vitro model of the epithelial barrier. Conclusion: These preliminary data indicate that EPC/SDCh liposomes may have a promising future in vaginal delivery of metronidazole. Therefore, additional investigations on elastic vesicles and their incorporation in a suitable vehicle should be considered to further evaluate their applicability in vaginal drug delivery.

Fusogenic activity of PEGylated pH-sensitive liposomes

The aim of this study was to investigate the fusogenic properties of poly(ethylene glycol) (PEG)ylated dioleoylphosphatidylethanolamine/cholesteryl hemisuccinate (DOPE/CHEMS) liposomes. These pH-sensitive liposomes were prepared by incorporating two different PEG lipids: Distearoylphosphatidylethanolamine (DSPE)-PEG2000 was mixed with the liposomal lipids using the conventional method, whereas sterol-PEG1100 was inserted into the outer monolayer of preformed vesicles. Both types of PEGylated liposomes were characterized and compared for their entrapment efficiency, zeta potential and size, and were tested in vitro for pH sensitivity by means of proton-induced leakage and membrane fusion activity. To mimic the routes of intracellular delivery, fusion between pH-sensitive liposomes and liposomes designed to simulate the endosomal membrane was studied. Our investigations confirmed that DOPE/CHEMS liposomes were capable of rapidly releasing calcein and of fusing upon acidification. However, after incorporation of DSPE-PEG2000 or sterol-PEG1100 into the membrane, pH sensitivity was significantly reduced; as the mol ratio of PEG-lipid was increased, the ability to fuse was decreased. Comparison between two different PEGylated pH-sensitive liposomes showed that only vesicles containing 0.6 mol% sterol-PEG1100 in the outer monolayer were still capable of fusing with the endosome-like liposomes and showing leakage of calcein at pH 5.5.

Liposomes for (trans)dermal drug delivery: the skin-PVPA as a novel in vitro stratum corneum model in formulation development

Abstract Penetration potential of vesicles destined for trans(dermal) administration remains to be of great interests both in respect to drug therapy and cosmetic treatment. This study investigated the applicability of the phospholipid vesicle-based permeation assay (PVPA) as a novel in vitro skin barrier model for screening purposes in preformulation studies. Various classes of liposomes containing hydrophilic model drug were examined, including conventional liposomes (CLs), deformable liposomes (DLs) and propylene glycol liposomes (PGLs). The size, surface charge, membrane deformability and entrapment efficiency were found to be affected by the vesicle lipid concentration, the presence of the surfactant and propylene glycol. All liposomes exhibited prolonged drug release profiles with an initial burst effect followed by a slower release phase. The permeation of the drug from all of the tested liposomes, as assessed with the mimicked stratum corneum – PVPA model, was significantly enhanced as compared to the permeability of the drug in solution form. Although the DLs and the PGLs exhibited almost the same membrane elasticity, the permeability of the drug delivered by PGLs was higher (6.2 × 10−6 cm/s) than DLs (5.5 × 10−6 cm/s). Therefore, this study confirmed both the potential of liposomes as vesicles in trans(dermal) delivery and potential of the newly developed skin-PVPA for the screening and optimization of liposomes at the early preformulation stage.

Mucosal nanosystems for improved topical drug delivery: vaginal route of administration

This review represents an attempt to summarize the current developments in the area of mucosal drug delivery destined for localized effects, address the challenges and comment on the potentials this therapy approach offers. Among different mucosal drug delivery systems currently available in the pipelines of pharmaceutical development, we have focused on the delivery systems in nanosize range, as they offer certain advantages which will be herewith discussed in more details. According to their surface properties, mucosal nanosystems are generally classified as conventional (non-mucoadhesive), mucoadhesive and mucus-penetrating nanosystems, while on the structural basis they are often classified as lipid- and polymer-based nanoparticles. Particular emphasis was put on nanosystems for topical vaginal therapy. Most of the presented nanosystems are destined for improved treatment of vaginitis and prevention of sexually transmitted viral diseases.

Tablets of pre-liposomes govern in situ formation of liposomes: Concept and potential of the novel drug delivery system

The purpose of this study was to develop a novel drug delivery system for challenging drugs with potential for scale-up manufacturing and controlled release of incorporated drug. Pre-liposomes powder containing metronidazole, lecithin and mannitol, prepared by spray-drying, was mixed with different tableting excipients (microcrystalline cellulose, lactose monohydrate, mannitol, dibasic calcium phosphate, pregelatinized starch, pectin or chitosan) and compressed into tablets. The delivery system was characterized with respect to (i) dry powder characteristics, (ii) mechanical tablet properties and drug release, and (iii) liposomal characteristics. The pre-liposomes powder was free-flowing, and tablets of similarly high qualities as tablets made of physical mixtures were prepared with all excipients. Liposomes were formed in situ upon tablet disintegration, dissolution or erosion depending on the type of tablet excipient used. The liposomal characteristics and drug release were found to depend on the tablet excipient. The new delivery system offers a unique synergy between the ability of liposomes to encapsulate and protect drugs and increased stability provided by compressed formulations. It can be adjusted for drug administration via various routes, e.g. oral, buccal and vaginal.

An overview of in vitro dissolution/release methods for novel mucosal drug delivery systems

HighlightsMucosal delivery systems differ in physicochemical and release characteristics.Versatile in vitro release methods are currently used for their characterisation.Compendial methods are used as a first approach whenever applicable.Novel biorelevant methods are needed for the prediction of performance in vivo. ABSTRACT In vitro dissolution/release tests are an important tool in the drug product development phase as well as in its quality control and the regulatory approval process. Mucosal drug delivery systems are aimed to provide both local and systemic drug action via mucosal surfaces of the body and exhibit significant differences in formulation design, as well as in their physicochemical and release characteristics. Therefore it is not possible to devise a single test system which would be suitable for release testing of such complex dosage forms. This article is aimed to provide a comprehensive review of both compendial and noncompendial methods used for in vitro dissolution/release testing of novel mucosal drug delivery systems aimed for ocular, nasal, oromucosal, vaginal and rectal administration.

Lipid-Based Nanopharmaceuticals in Antimicrobial Therapy

Nanotechnology and its direct application in medicine offer a platform for advanced therapeutic strategies against infections. The small size of nanosystems (nanocarriers) distinguishes their features from other delivery systems since nanocarriers may penetrate biological membranes, improve drug bioavailability, assure cellular internalization and often achieve targeted delivery of various drugs, including antimicrobials. Lipid-based nanosystems, in addition to their confirmed biodegradability and biocompatibility, allow fusion with infectious microbes, facilitating the release of the drug intracellularly. This chapter summarizes the most studied lipid-based nanocarriers, their applications via various routes of drug administration, their advantages in comparison to other drug dosage forms and delivery systems, the toxicity issues and current limitations. Based on authors’ experience in the research related to therapy of vaginal and skin infections, those routes are discussed in more details. The promising lines in lipid-based nanopharmaceutical research are highlighted.