Was examined the potential for using tyrosinase to graft the polysaccharide chitosan (Ch) onto silk fibroin (SF). Mushroom tyrosinase was observed to catalyse the oxidation of tyrosine of SF in aqueous solution. The amino acid composition of oxidized SF showed a decrease of tyrosine concentration. Chemical changes were confirmed by FT-IR spectroscopy. Tyrosinase converts the phenolic substrate into electrophilic o-quinones, which undergo a subsequent non-enzymatic reaction with nucleophilic amino groups of chitosan. Using slightly acidic conditions (pH = 6) it was possible to modify silk fibroin under homogeneous conditions and synthetize SF/Ch bioconjugates. The FT-IR spectra provided evidence that chitosan was grafted onto silk fibroin. The feasibility of the enzymatic activation of SF, followed by the non-enzymatic coupling with Ch was investigated under heterogeneous reaction conditions. Preliminary results obtained by using SF in form of gel, powder and fibre will be reported.
Silk fibroin-chitosan bioconjugates obtained by enzymatic grafting.
TADDEI, PAOLA;MONTI, PATRIZIA;
2004
Abstract
Was examined the potential for using tyrosinase to graft the polysaccharide chitosan (Ch) onto silk fibroin (SF). Mushroom tyrosinase was observed to catalyse the oxidation of tyrosine of SF in aqueous solution. The amino acid composition of oxidized SF showed a decrease of tyrosine concentration. Chemical changes were confirmed by FT-IR spectroscopy. Tyrosinase converts the phenolic substrate into electrophilic o-quinones, which undergo a subsequent non-enzymatic reaction with nucleophilic amino groups of chitosan. Using slightly acidic conditions (pH = 6) it was possible to modify silk fibroin under homogeneous conditions and synthetize SF/Ch bioconjugates. The FT-IR spectra provided evidence that chitosan was grafted onto silk fibroin. The feasibility of the enzymatic activation of SF, followed by the non-enzymatic coupling with Ch was investigated under heterogeneous reaction conditions. Preliminary results obtained by using SF in form of gel, powder and fibre will be reported.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
