CHITOSAN-MEDIATED STIMULATION OF MACROPHAGE FUNCTION

According to the modern definition of biocompatibility, a biocompatibl e material need not be inert but be bioactive. A benign reactivity imp lies that the reactivity has to be appropriate for the intended use. C hitosan, a non-acetylated or partially deacetylated chitin (a linear h omopolymer of beta(1-4)-linked N-acetylglucosamine) has been proposed as a biomaterial because of its apparent satisfactory biocompatibility , The present investigation demonstrates that chitosan has an in vitro stimulatory effect on both macrophage nitric oxide (NO) production an d chemotaxis. The macrophage NO secretion is attributed to the N-acety lglucosamine unit of the chitosan molecule rather than to the glucosam ine residue (28 and 15 mu M NO respectively). Moreover, the immune sti mulatory effect of chitosan was very specific since other glycosaminog lycans, such as N-acetyl-D-mannosamine and N-acetyl-D-galactosamine, h ad no effects on NO production (5 and 8 respectively). In vivo experim ents strengthen this hypothesis. Transmission electron microscopy anal ysis identifies the presence of many leucocytes in the specimens after 14 d post-implantation, showing poor healing processes (i.e, fibrobla st proliferation and collagen deposition) that characterize the tissue repair at this time in our animal model.