Glycerin and ethanol as additives on silk fibroin films: Insoluble and malleable films

Silk fibroin (SF) films have been largely studied as biomaterials due to their biocompatibility and biodegradability. Casting a SF aqueous solution at room temperature is a common technique to produce SF films at relative low cost and processing time; however, their brittleness and solubility in water make them unsuitable for certain biomedical applications. In this study, the incorporation of additives, ethanol and glycerin, are presented as an alternative to both improve mechanical properties of SF films and decrease their solubility in water. SF films with additives were further characterized using scanning electron microscopy, X-ray diffraction, Fourier transformed infrared spectroscopy with attenuated total reflection, analysis of water solubility, mechanical test of traction, and in vitro cytotoxicity experiments. The results show that SF films containing additives are stable in water due to the effect of glycerin and ethanol, and do not require post-treatments. Furthermore, great improvements on elongation of the films were achieved, mainly in the presence of both additives. In addition, all films were not toxic to cells, which is a first indication of their biocompatibility. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013