The texture properties of formulation are an important parameter in optimization of topical formulations. These properties will affect applicability of the formulation at the administration site and therapy outcome. Our aim was to develop a fast and reliable method to characterize texture properties of hydrogels, namely cohesiveness, adhesiveness, and hardness. During the method development, we realized that the measurements setup needed to be adjusted for each hydrogel type, namely Carbopol, chitosan, and poloxamer hydrogels. The influence of the polymer concentration, pH, and incorporation of additives such as glycerol, drug solution, or liposomes on the texture properties, as determined by Texture Analyzer, was evaluated. In addition, the new method was applied to determine the changes during the accelerated stability testing. While Carbopol and poloxamer gels showed a linear relationship between the polymer concentration and texture properties, for low molecular weight chitosan gels the properties increased in exponential manner with increasing polymer concentration. The effect of incorporated liposomes on the gel properties was found to be dependent on the type of hydrogel. The hydrogel hardness was affected by the temperature as seen in accelerated stability testing. The method represents a valuable tool in pharmaceutical and cosmetics formulation development. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

18To study the release of liposome-associated drugs into hydrogels, we designed and hydrogels than the neutral ones. In respect to the ability of the system to handle wound 32 exudates, chitosan-based hydrogels were found to be superior to Carbopol-based hydrogels.

No abstract

Chitosan is currently proposed to be one of the most promising polymers in wound dressing development. Our research focuses on its potential as a vehicle for nano-delivery systems destined for burn therapy. One of the most important features of wound dressing is its bioadhesion to the wounded site. We compared the bioadhesive properties of chitosan with those of Carbopol, a synthetic origin polymer. Chitosan-based hydrogels of different molecular weights were first analyzed by texture analysis for gel cohesiveness, adhesiveness and hardness. In vitro release studies showed no difference in release of model antimicrobial drug from the different hydrogel formulations. Bioadhesion tests were performed on pig ear skin and the detachment force, necessary to remove the die from the skin, and the amount of remaining formulation on the skin were determined. Although no significant difference regarding detachment force could be seen between Carbopol-based and chitosan-based formulations, almost double the amount of chitosan formulation remained on the skin as compared to Carbopol formulations. The findings confirmed the great potential of chitosan-based delivery systems in advanced wound therapy. Moreover, results suggest that formulation retention on the ex vivo skin samples could provide deeper insight on formulation bioadhesiveness than the determination of detachment force.

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.