Franca Ferrari

Characterization of chitosan hydrochloride–mucin interaction by means of viscosimetric and turbidimetric measurements

In the present work the interaction between chitosan hydrochloride (HCS) and two different types of mucin - one obtained from bovine submaxillary glands and the other from porcine stomach - was investigated. Two hydration media were tested: distilled water and 0. 1 M HCl. Intrinsic viscosity, which provides information about polymeric chain conformation, was assessed in both media for HCS and bovine submaxillary mucin. Changes in the specific viscosity of HCS-mucin mixtures were observed as a function of the polymer:mucin weight ratio. The formation of interaction products was indicated by a minimum in the specific viscosity. Such a minimum occurred at different polymer:mucin weight ratios depending on the hydration medium and mucin type. This suggested a different stoichiometry of interaction. Turbidimetric measurements were also effected in order to evidentiate the eventual precipitation of the polymer-mucin interaction products. While in distilled water the precipitation of the interaction product did occur, in acidic medium, although a minimum in specific viscosity was observed, no precipitate was formed. The two techniques employed, viscosimetric and turbidimetric, allowed us to investigate for both mucins the influence of hydration medium on the formation of the HCS-mucin interaction products and to conclude that a slightly acid-neutral pH favours the interaction between HCS and mucins.

Cyclosporine A loaded SLNs: evaluation of cellular uptake and corneal cytotoxicity.

Cyclosporine A (CsA) loaded solid lipid nanoparticles (SLNs) for topical ophthalmic applications were prepared by high shear homogenization and ultrasound method using Compritol 888 ATO, Poloxamer 188 and Tween 80, to investigate the cellular uptake of rabbit corneal epithelial cells (RCE) and to evaluate the cytotoxicity. The size of the optimized formulation was 225.9+/-5.5 nm with a polydispersity index of 0.253+/-0.05. The zeta potential and entrapment efficiency was detected as -16.9+/-0.7 mV and 95.6%, respectively. The CsA release was found to be enzyme (lipase/co-lipase complex) dependent. SLNs were sterilized at 110 and 121 degrees C. The cytotoxicity was evaluated in vitro by means of RCE cells and was higher at 121 degrees C sterilization temperature, probably due to a supposed leakage of Tween 80 following lipid re-crystallization. The permeation and penetration of CsA across/into the corneal cells were evaluated using in vitro and ex vivo experiments. The cellular uptake was investigated by replacing CsA with the fluorescent dye Rhodamine B. The penetration enhancement properties were supported by confocal laser scanning microscopy analysis. The internalization of SLNs in cornea and in RCE cell lines was confirmed, pointing out the possibility of CsA targeting to the cornea.

Buccal Delivery of Acyclovir from Films Based on Chitosan and Polyacrylic Acid

The aim of the present work was to investigate the possibility of achieving buccal delivery of a problematic drug, acyclovir, from films based on chitosan hydrochloride (HCS) and polyacrylic acid sodium salt (PAA). At first, the ionic interaction between HCS and PAA in distilled water was investigated by means of rheological and turbidimetric analysis. Films containing 1 mg/cm2 of acyclovir and based on pure HCS and on HCS and PAA mixed in different ratios were prepared by casting technique. The films were subjected to hydration, rheological, mucoadhesion, drug release, “wash away,” and permeation/penetration measurements. A commercial cream containing acyclovir and an aqueous acyclovir suspension were used as references. The addition of PAA to HCS produced a decrease in film hydration. Films based on HCS/PAA weight ratio close to interaction product stoichiometry were characterized by higher rigidity and better “wash away” properties with respect to the other films and the reference formulation. The worst mucoadhesive properties were shown by films based on mixing ratios close to interaction product stoichiometry. The addition of PAA to HCS produced a lowering in drug release profile. All the films examined promoted the permeation of acyclovir across porcine cheek epithelium when compared with acyclovir suspension and the commercial cream. The penetration enhancement properties were affected by the mixing ratio of the two polymers. The film based on 1/1.3 HCS/PAA weight ratio, besides possessing the best resilience properties on the mucosa, was also characterized by the highest permeation profile and, therefore, represents a promising formulation for buccal delivery of acyclovir.

Influence of mucin type on polymer-mucin rheological interactions

There are numerous in vitro methods with which to investigate the mucoadhesive properties of polymers. One recent method is based on the measurement of rheological interactions between polymer and mucin, which implies the use of mucins isolated from the mucous tissue. The extraction and purification of glycoprotein fraction, which is responsible for rheological interaction, can modify the native structure of mucin or spoil it with exogenous substances. Therefore the particulars of the mucin employed (origin, purification grade, the effect of further treatments such as freezing or freeze-drying) are likely to be critical for the interaction. The aim of this work was to compare some commercial mucins of differing origin and grade of purification for their rheological interaction with well-known mucoadhesive polymers (polyacrylic acid and sodium carboxymethylcellulose). For polyacrylic acid, which is sensitive to ions, we found rheological interaction to be strongly influenced by mucin type. The removal of ions, with dialysis, improved the interaction. For sodium carboxymethylcellulose, which is less sensitive to ions, rheological interaction proved to be less dependent on mucin type and improved upon glycoprotein solubilization.

Mucoadhesive and thermogelling systems for vaginal drug delivery.

This review focuses on two formulation approaches, mucoadhesion and thermogelling, intended for prolonging residence time on vaginal mucosa of medical devices or drug delivery systems, thus improving their efficacy. The review, after a brief description of the vaginal environment and, in particular, of the vaginal secretions that strongly affect in vivo performance of vaginal formulations, deals with the above delivery systems. As for mucoadhesive systems, conventional formulations (gels, tablets, suppositories and emulsions) and novel drug delivery systems (micro-, nano-particles) intended for vaginal administration to achieve either local or systemic effect are reviewed. As for thermogelling systems, poly(ethylene oxide-propylene oxide-ethylene oxide) copolymer-based and chitosan-based formulations are discussed as thermogelling systems. The methods employed for functional characterization of both mucoadhesive and thermogelling drug delivery systems are also briefly described.

Mucoadhesive and penetration enhancement properties of three grades of hyaluronic acid using porcine buccal and vaginal tissue, Caco‐2 cell lines, and rat jejunum

The influence of the molecular weight on mucoadhesive and penetration enhancement properties of three grades of hyaluronic acid (1878, 693 and 202 kDa) has been evaluated. The mucoadhesive properties were investigated using buccal and vaginal porcine mucosa by means of a tensile stress method and using rat jejunum by means of an inclined plane method. The mucoadhesive performances observed using animal tissues were compared with the mucoadhesive properties observed using submaxillary or gastric mucin dispersions. The penetration enhancement properties were investigated using porcine buccal epithelium membrane or vaginal tissue and a cell monolayer (Caco‐2 cell line). Chitosan hydrochloride, already described as a penetration enhancer towards buccal and vaginal mucosae and Caco‐2 cell monolayers, was used as reference. Aciclovir (acyclovir), a poorly soluble and absorbable drug, commonly used in the treatment of Herpes simplex virus (type I and II), was used as the model drug. Unlike chitosan hydrochloride, which does not show any mucoadhesive potential at pH close to neutrality (buccal and intestinal), all hyaluronic acid grades show mucoadhesive properties in all the environments considered (buccal, vaginal and intestinal). In all cases, a decrease in molecular weight of hyaluronic acid produced an increase in the mucoadhesive performance. The hyaluronic acid with the lowest molecular weight (202 kD) exhibited the best penetration enhancement properties, that, depending on the substrate under consideration, was either comparable with or even better than chitosan hydrochloride. Therefore, this grade would be the most promising for buccal, vaginal and intestinal delivery of aciclovir.

On the employment of lambda carrageenan in a matrix system. III. Optimization of a lambda carrageenan-HPMC hydrophilic matrix

The lambda carrageenan/HPMC ratio in matrix tablets has been optimized in order to obtain pH-independent release profiles of chlorpheniramine maleate, a freely soluble drug. Release profiles in acidic (pH1.2) and neutral (pH 6.8) media were fitted according to the Weibull and the power law models. Model independent parameters(t50% and the percentage of drug released after 2 h) were also calculated. The Weibull parameters were found suitable to describe the dependence of the release profiles on matrix composition. Preparation and testing of the optimized formulation showed linear and pH-independent release profiles lasting about 24 h, in good accordance with the values predicted by the optimization procedure.

Chitosan and its salts for mucosal and transmucosal delivery

This review considers the application of chitosan and its salts in the delivery of drugs intended to act locally towards diseases of the mucosa itself (mucosal delivery), and to undergo systemic absorption by means of transmucosal routes (transmucosal delivery). Those chitosan properties that are particularly useful in mucosal and transmucosal delivery have been reviewed, such as mucoadhesion, penetration enhancement and peptidase inhibition behaviour. Chitosan bioactive properties have also been considered, such as anti-infective, haemostatic, wound healing and immune-stimulating activity. Chitosan is available with a wide range of molecular mass and deacetylation degree: the influence of these properties on polymer performance and solubility has been taken into account. As solubility in particular can strongly limit the results obtained at pH values close to neutrality, particular attention has been paid to chitosan salts and derivatives with modified solubility. Thanks to the presence of positively charged amino groups of the polymer, a subject of increasing interest is the exploitation of its interaction with acidic molecules having potential synergistic behaviour towards bioactive properties, or even with acidic drugs. The aim of the review is to describe not only some properties of chitosan, but also the way they can be modified by the acidic moiety.

The Surface Roughness of Lactose Particles Can Be Modulated by Wet- Smoothing Using a High-Shear Mixer

The surface morphology of α-lactose monohydrate particles was modified by a new wet-smoothing process performed in a high-shear mixer using solvents. Successive steps of wetting and drying of lactose powders during rolling in the mixers cylindrical bowl were performed. Smoothed particles were tested for size distribution, flow, and packing. The wet-smoothing process flattened the surface and rounded the edges of lactose particles. In comparison with original lactose, an improvement of powder packing and flow properties was evidenced. When the process was performed in the presence of a ternary agent such as magnesium stearate, the smoothing was improved. The evolution of rugosity during the smoothing process was assessed through a fractal descriptor of SEM picture. Atomic force microscopy and surface area measurements quantified the surface rugosity. A very significant reduction of the rugosity, more remarkable in the presence of magnesium stearate, was measured. This new process of powder wet-smoothing allows the preparation of lactose particles with different degrees of smoothed surface for the control of flow and packing properties and particle-particle interactions.

Characterization of a diltiazem-lambda carrageenan complex

In the present paper the interaction between lambda carrageenan, a natural sulphated polysaccharide, and diltiazem HCl, a Ca channel blocking agent, was studied. Dialysis equilibria were performed to quantify the binding capacity of lambda carrageenan for diltiazem. The relevance of the interaction to hydrophilic matrix systems was confirmed: a relationship was found between the binding capacity and the release profiles of matrix tablets containing a fixed amount of drug and different percentages of lambda carrageenan. Dialysis equilibria in buffered media showed that the interaction is quite insensitive to the pH of the medium (in the range 1.8-6.8), while it is reduced by increasing ionic strength; this behaviour is in line with the importance of ionic bonds in diltiazem-carrageenan interaction. On the basis of the calculated binding capacity, the complex was prepared, dried and milled. A preliminary characterization of the diltiazem-carrageenan complex in the solid state was effected by means of X-ray and DSC analysis. The amount of drug going into solution from the complex was not significantly affected by the pH of the medium (in the range 1.8-6.8), while it was increased by increasing ionic strength.