Kawthar Bouchemal

Dehydration, dissolution, and melting of cyclodextrin crystals.

Cyclodextrins are a family of oligosaccharides with a toroid shape that exhibit a unique ability of entrapping guest molecules in their internal cavity. Water is the primary guest molecule and is omnipresent in the crystalline phases stabilizing the overall architecture. Despite the presence of water molecules inside the cavity, cyclodextrins provide a hydrophobic environment where poorly soluble molecules can easily fit. In this investigation we put in evidence different types of water in the hydrated α-, β-, and γ-cyclodextrin crystals. Thermogravimetric measurements identify various binding sites of water and highlight the difference between the crystals equilibrated under various humid atmospheres. We establish by microcalorimetry the limit of solubility versus temperature and measure for the first time the melting temperatures of the hydrated crystals. Dissolution and melting enthalpies are derived and the solubility curves are compared to existing literature. The specific features of each cyclodextrin are underlined.

In situ forming pluronic® F127/chitosan hydrogel limits metronidazole transmucosal absorption

Graphical abstract Figure. No caption available. Abstract The objective of this work is to design topically‐applied thermosensitive and mucoadhesive hydrogel containing metronidazole (MTZ) for the treatment of Trichomonas vaginalis infections. Hydrogel composed of pluronic® F127 (20 wt%), chitosan (1 wt%) and metronidazole MTZ (0.7 wt%) mixture showed its ability to decrease by a factor 4 MTZ flux and apparent permeability absorption through vaginal mucosa. The impact of hydrogel on transmucosal penetration of MTZ was evaluated ex vivo on excised porcine vaginal mucosa mounted on Franz diffusion cell. The anti‐T. vaginalis activity of MTZ formulated into F127/chitosan hydrogel was preserved since the viability curve evaluated in vitro was similar to MTZ solution.

Gelation and micellization behaviors of pluronic® F127 hydrogel containing poly(isobutylcyanoacrylate) nanoparticles specifically designed for mucosal application

The aim of this investigation is to combine the advantages of pluronic(®) F127 hydrogels and nanoparticles composed of poly(isobutylcyanoacrylate) (PIBCA) core coated with a mixture of chitosan and thiolated chitosan to design novel multifunctional formulation for mucosal application. Nanoparticles offer the advantage of being mucoadhesive while pluronic(®) F127 hydrogel allowed prolonged contact time onto mucosal surfaces. This work highlights an unprecedented comprehensive study on the effect of nanoparticles on gelation and micellization behaviors of pluronic(®) F127 using rheology and micro-calorimetry experiments. Results showed that presence of nanoparticles induced (i) smaller crystal peak of F127, (ii) a decrease of the enthalpy of F127 micellization and (iii) a non-reversibility of micelle formation (during heating ramp) and micelle melting (during cooling ramp). Together, these findings suggest that a part of F127 was not able to associate into micelles and the formation of mixed micelles containing F127 unimers and PIBCA/(chitosan/thiolated chitosan) copolymer and/or PIBCA homopolymer was suspected. The interaction of F127 unimers with nanoparticles resulted from their physical de-structuration as revealed by nanoparticle size measurement. In addition, we found that short polymerization duration of one hour induced more pronounced nanoparticle de-structuration. Twenty-four hour-polymerization of isobutylcyanoacrylate in the presence of chitosan and thiolated chitosan led to more stable nanoparticles when mixed with pluronic(®) F127.

Auto-associative heparin nanoassemblies: a biomimetic platform against the heparan sulfate-dependent viruses HSV-1, HSV-2, HPV-16 and RSV.

A new, simple and green method was developed for the manufacturing of heparin nanoassemblies active against the heparan sulfate-dependent viruses HSV-1, HSV-2, HPV-16 and RSV. These nanoassemblies were obtained by the auto-association of O-palmitoyl-heparin and α-cyclodextrin in water. The synthesized O-palmitoyl-heparin derivatives mixed with α-cyclodextrin resulted in the formation of crystalline hexagonal nanoassemblies as observed by transmission electron microscopy. The nanoassembly mean hydrodynamic diameters were modulated from 340 to 659 nm depending on the type and the initial concentration of O-palmitoyl-heparin or α-cyclodextrin. The antiviral activity of the nanoassemblies was not affected by the concentration of the components. However, the method of the synthesis of O-palmitoyl-heparin affected the antiviral activity of the formulations. We showed that reduced antiviral activity is correlated with lower sulfation degree and anticoagulant activity.

Cyclodextrin-mediated self-associating chitosan micro-platelets act as a drug booster against Candida glabrata mucosal infection in immunocompetent mice

This study reports design and evaluation of chitosan-based microparticle activity against Candida glabrata in vitro and in vivo in immunocompetent mice model artificially maintained in oestrus state. Because their flattened shape, chitosan microparticles are called here micro-platelets. They were obtained by self-association of oleoyl chitosan and α-cyclodextrin in water. A mixture of amphotericin B-deoxycholate (Fungizone®, AmB-DOC) and chitosan micro-platelets gelified with pluronic® F127 (20wt%) completely cured C. glabrata vaginal infection. Colony factor unit counting and mycological analysis of mice vaginal mucosa after Grocott-Gomori methenamine-silver staining confirmed the absence of C. glabrata. Furthermore, in vitro evaluations revealed that IC50 and MIC90 of AmB-DOC were decreased 1.8 and 1.4-times respectively when associated with chitosan micro-platelets. Neither native chitosan nor oleoyl chitosan allowed improvement in AmB-DOC anti-C. glabrata activity. This work demonstrates for the first time that a simple mixing of chitosan micro-platelets with AmB-DOC enhanced its anti-C. glabrata activity.

Strategies for Prevention and Treatment of Trichomonas vaginalis Infections

SUMMARY The last estimated annual incidence of Trichomonas vaginalis worldwide exceeds that of chlamydia and gonorrhea combined. This critical review updates the state of the art on advances in T. vaginalis diagnostics and strategies for treatment and prevention of trichomoniasis. In particular, new data on treatment outcomes for topical administration of formulations are reviewed and discussed.

Cell line-dependent cytotoxicity of poly(isobutylcyanoacrylate) nanoparticles coated with chitosan and thiolated chitosan: Insights from cultured human epithelial HeLa, Caco2/TC7 and HT-29/MTX cells

Nanoparticles composed of poly(isobutylcyanoacrylate) core coated with a mixture of chitosan and thiolated chitosan have already shown promising results in terms of mucoadhesion and permeation enhancement properties of pharmaceutical active drugs delivered via mucosal routes. In the present work, the cytotoxicity of these nanoparticles was first investigated using direct contact assay on undifferentiated human cervix epithelial HeLa cells. The results showed strong toxicity in HeLa cells for the two investigated concentrations 25 and 50 μg/mL. The cytotoxic effect was mainly attributed to the poly(isobutylcyanoacrylate) core since no significant differences in nanoparticle cytotoxicity were reported when nanoparticle shell composition was modified by adding chitosan or thiolated chitosan. In contrast, lower nanoparticle toxicity was reported using human fully-differentiated enterocyte-like Caco-2/TC7, and fully-differentiated mucus-secreting HT-29/MTX cells forming monolayer in culture mimicking an intestinal epithelial barrier. This study demonstrated that the toxicity of poly(isobutylcyanoacrylate) nanoparticles is highly cell line-dependent.

Hexagonal-shaped chondroitin sulfate self-assemblies have exalted anti-HSV-2 activity.

The initial step in mucosal infection by the herpes simplex virus type 2 (HSV-2) requires its binding to certain glycosaminoglycans naturally present on host cell membranes. We took advantage of this interaction to design biomimetic supramolecular hexagonal-shaped nanoassemblies composed of chondroitin sulfate having exalted anti-HSV-2 activity in comparison with native chondroitin sulfate. Nanoassemblies were formed by mixing hydrophobically-modified chondroitin sulfate with α-cyclodextrin in water. Optimization of alkyl chain length grafted on chondroitin sulfate and the ratio between hydrophobically-modified chondroitin sulfate and α-cyclodextrin showed that more cohesive and well-structured nanoassemblies were obtained using higher α-cyclodextrin concentration and longer alkyl chain lengths. A structure-activity relationship was found between anti-HSV-2 activity and the amphiphilic nature of hydrophobically-modified chondroitin sulfate. Also, antiviral activity of hexagonal nanoassemblies against HSV-2 was further improved in comparison with hydrophobically-modified chondroitin sulfate. This work suggests a new biomimetic formulation approach that can be extended to other heparan-sulfate-dependent viruses.

Supramolecular Chitosan Micro-Platelets Synergistically Enhance Anti-Candida albicans Activity of Amphotericin B Using an Immunocompetent Murine Model

PurposeThe aim of this work is to design new chitosan conjugates able to self-organize in aqueous solution in the form of micrometer-size platelets. When mixed with amphotericin B deoxycholate (AmB-DOC), micro-platelets act as a drug booster allowing further improvement in AmB-DOC anti-Candida albicans activity.MethodsMicro-platelets were obtained by mixing oleoyl chitosan and α-cyclodextrin in water. The formulation is specifically-engineered for mucosal application by dispersing chitosan micro-platelets into thermosensitive pluronic® F127 20 wt% hydrogel.ResultsThe formulation completely cured C. albicans vaginal infection in mice and had a superior activity in comparison with AmB-DOC without addition of chitosan micro-platelets. In vitro studies showed that the platelets significantly enhance AmB-DOC antifungal activity since the IC50 and the MIC90 decrease 4.5 and 4.8-times. Calculation of fractional inhibitory concentration index (FICI = 0.198) showed that chitosan micro-platelets act in a synergistic way with AmB-DOC against C. albicans. No synergy is found between spherical nanoparticles composed poly(isobutylcyanoacrylate)/chitosan and AmB-DOC.ConclusionThese results demonstrate for the first time the ability of flattened chitosan micro-platelets to have synergistic activity with AmB-DOC against C. albicans candidiasis and highlight the importance of rheological and mucoadhesive behaviors of hydrogels in the efficacy of the treatment.

Pickering emulsions with α-cyclodextrin inclusions: Structure and thermal stability.

This paper explores structural, interfacial and thermal properties of two types of Pickering emulsions containing α-cyclodextrin inclusion complexes: on one hand, emulsions were obtained between aqueous solutions of α-cyclodextrin and different oils (fatty acids, olive oil, silicone oil) and on the other hand, emulsions were obtained between these oils, water and micro or nano-platelet suspensions with inclusion complexes of hydrophobically-modified polysaccharides. The emulsions exhibit versatile properties according to the molecular architecture of the oils. Experiments were performed by microcalorimetry, X-ray diffraction and confocal microscopy. The aptitude of oil molecules to be threaded in α-cyclodextrin cavity is a determining parameter in emulsification and thermal stability. The heat flow traces and images showed dissolution, cooperative melting and de-threading of inclusion complexes which take place progressively, ending at high temperatures, close or above 100°C. Another important feature observed in the emulsions with micro-platelets is the partial substitution of the guest molecules occurring at room temperature at the oil/water interfaces without dissolution, possibly by a diffusion mechanism of the oil. Accordingly, the dissolution and the cooperative melting temperatures of the inclusion crystals changed, showing marked differences upon the type of guest molecules. The enthalpies of dissolution of crystals were measured and compared with soluble inclusions.