Interactions between chitosan and glycosaminoglycans (chondroitin sulfate and hyaluronic acid): physicochemical and biological studies.

Chitosan is a polysaccharide well known for its numerous and interesting biological properties, indeed, it is a biocompatible, bioresorbable and bioactive biopolymer. It is therefore often introduced in the human body, where it happens to be in contact with glycosaminoglycans (GAG's), especially chondroitin sulfates and hyaluronic acid which play important part in living media. Thus it seems interesting to consider systems associating chitosan and GAG's. The aim of our work is to study the mechanism of formation of biomaterials constituted of chitosan and GAG's which could have interesting biological properties such as improving the wound-healing acceleration and the cellular assistance for skin and cartilage recovery. In the same time, it was interesting to try to understand what can happen when chitosan is introduced in a natural surrounding containing GAG's. In a first part, the complexes between chitosan and GAG's were characterised by various physicochemical techniques: pH-metry, conductometry and Infra-red spectrometry. They appeared to be polyelectrolyte complexes obtained by the formation of polyanion-polycation interactions held between ammonium functions of chitosan and carboxylate and/or sulfate groups of GAG's. The complexes formed are very strong and can, in some cases, even conduct to the deprotonation of carboxylic functions. In a second part we considered the biological properties of the complexes previously obtained. The hydrolysis activity in presence of specific enzymes was investigated. We also studied the cytocompatibility of chitosan alone and its complexes with the two considered GAG's toward two kinds of cells (chondrocytes and keratinocytes). At the end of the work, a short animal experimentation on rats was performed allowing the comparison between in vitro and in vivo results.