Cellular responses to chitosan in vitro: The importance of deacetylation

Chitin and chitosan (a deacetylated derivative of chitin) have been propose d for biomedical applications because of their biocompatibility and abundan ce in nature. We have investigated the effect of the percentage of deacetyl ation (%DD) of chitosan on biocompatibility from two sources, shrimp and cu ttle fish, with two cell lines, L929 and BHK21(C13). The difference in %DD for each source was approximately 10% in the range of 76-90%. Biocompatibil ity was investigated for: (1) cell adherence and growth on the chitosan sam ples as substrate; (2) the effect of extract media on 2d and 7d growth; and (3) the presence of an inhibition zone. The results were similar for both cell lines. The chitosan samples were air-dried on to tissue culture-grade petri dishes to provide a substrate for the adherent-cell cultures. The hig her %DD substrates from each source supported attachment of the cells, whil e the lower %DD did not. Cells cultured in medium conditioned by each subst rate (i.e. extract medium) displayed an initial difference in growth which was abrogated in cultures incubated for 7 days. No inhibition zone was appa rent. However, after 7 days, some cells were noted migrating on to the low %DD substrate disks. The morphology of these cells was changed with the pre sence of pseudopodia being apparent. Thus, especially with regard to attach ment the %DD has a very important effect on the biocompatibility of the chi tosan and should be monitored carefully. (C) 2000 Kluwer Academic Publisher s.