In this study, A. pernyi silk fibroin (Ap-SF) films were incubated with Protease Type XXI from Streptomyces griseus, at 37°C, to investigate the degradation behaviour in an in vitro model system. The enzyme-resistant fractions of Ap-SF films and the soluble peptides formed by proteolytic degradation were collected at specified times, from 1 to 17 days, and analyzed by high performance liquid chromatography (HPLC), differential scanning calorimetry (DSC), FT-Raman and FT-IR spectroscopy. Proteolysis resulted in extensive weight loss and progressive fragmentation of films, especially at long degradation times. A range of soluble peptides was formed by proteolysis. By HP-size exclusion chromatography it was found that their average molecular weight changed with the time of incubation. The chemical analysis of the enzyme-resistant fraction of Ap-SF films at different times of degradation indicated that the proteolytic attack preferentially occurred in the less ordered Gly-rich sequences, and that the Ala-rich crystalline regions of biodegraded films were enriched. Accordingly, DSC and spectroscopic results showed an enhancement of the crystalline character of the biodegraded films. From the behaviour of the most important thermal transitions it was deduced that the -helix domains probably represent the most enzyme-resistant fraction. The in vitro approach used in the present study seems a valid tool for studying the rate and mechanism of degradation of Ap-SF films and of other biopolymers of potential biomedical utility.
In vitro biodegradation study of tussah (A.pernyi) silk fibroin films.
TADDEI, PAOLA;MONTI, PATRIZIA;
2005
Abstract
In this study, A. pernyi silk fibroin (Ap-SF) films were incubated with Protease Type XXI from Streptomyces griseus, at 37°C, to investigate the degradation behaviour in an in vitro model system. The enzyme-resistant fractions of Ap-SF films and the soluble peptides formed by proteolytic degradation were collected at specified times, from 1 to 17 days, and analyzed by high performance liquid chromatography (HPLC), differential scanning calorimetry (DSC), FT-Raman and FT-IR spectroscopy. Proteolysis resulted in extensive weight loss and progressive fragmentation of films, especially at long degradation times. A range of soluble peptides was formed by proteolysis. By HP-size exclusion chromatography it was found that their average molecular weight changed with the time of incubation. The chemical analysis of the enzyme-resistant fraction of Ap-SF films at different times of degradation indicated that the proteolytic attack preferentially occurred in the less ordered Gly-rich sequences, and that the Ala-rich crystalline regions of biodegraded films were enriched. Accordingly, DSC and spectroscopic results showed an enhancement of the crystalline character of the biodegraded films. From the behaviour of the most important thermal transitions it was deduced that the -helix domains probably represent the most enzyme-resistant fraction. The in vitro approach used in the present study seems a valid tool for studying the rate and mechanism of degradation of Ap-SF films and of other biopolymers of potential biomedical utility.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
