Silk Fibroin Processing from CeCl3 Aqueous Solution: Fibers Regeneration and Doping with Ce(III)

Silk fibroin (SF) obtained from Bombyx mori cocoon is a very promising biopolymer. It can be processed from aqueous solutions to obtain many versatile scaffolds useful in optoelectronics, photonics, and biomedicine. Aqueous solutions are prepared by dissolving degummed fibroin with chaotropic agents and then purifying by dialysis. This work presents, for the first time, a solubilization protocol, involving CeCl7HO as chaotropic salt in water and ethanol, that allows to regenerate SF under a fibrous form, unlike the standard Ajisawa's method, which uses CaCl and allows to obtain aqueous gels. All the experimental analyses performed (SEM, XPS, WAXS, ATR-FTIR, NMR) suggest that the fiber recovered preserves most of the morphological and structural features of the pristine SF and is doped with Ce(III) ions, that interact mainly with the oxygen atoms of C-O moieties and side-chains of amino acids. Ce(III) doped SF could be the base for new luminescent materials.