Proteolytic degradation study of silk fibroin hydrogel

Silk has emerged as a useful protein polymer due to its biodegradability and utility in biomaterials for regenerative medicine and drug delivery. Silk fibroin hydrogels were prepared and studied in vitro with respect to enzymatic degradation using different proteases, including proteinase K, protease XIV, alpha-chymotrypsin, collagenase, and gelatinase A. Weight loss, secondary structure by Fourier Transform Infrared (FT-IR) spectroscopy and Circular Dichroism (CD), and protein fragments via sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) were used to assess the process. Quantitative changes in silk hydrogels resulted in relative enzymatic reactivity rates as follows: proteinase K > protease XIV > alpha-chymotrypsin > collagenase. The rate of degradation by gelatinase A was not directly comparable due to enzyme levels available for assay. Structural characterization of the hydrogels before and after degradation was performed by FT-IR and CD to confirm features of the degradation process. The data provide a basis for understanding and controlling degradation lifetimes of silk-based biomaterials in vitro with implications towards designed degradation rates in vivo.