Synthesis of hollow fibroin using calcium carbonate as a template

Silk fibroin is a unique biomaterial and has gained much attention in biomedical applications. In this study, we have demonstrated the formation of hollow fibroin using the selective etching method. Initially, spherical CaCO3 was synthesized in the presence of polyelectrolyte, poly(4-styrenesulfonate). CaCO3 particles were treated with aqueous silk fibroin solution, followed by methanol treatment. The sequential deposition of silk fibroin was achieved through a layer-by-layer (LbL) strategy to obtain fibroin-encapsulated CaCO3. Finally, the fibroin- encapsulated CaCO3 was treated with an acid solution to form hollow fibroin. The crystalline phase of as-prepared products was measured using powder X-ray diffraction, and vibrational modes of products were characterized using Fourier transform infrared spectroscopy. The hollow fibroin morphology was examined using electron microscopy. The resultant hollow fibroin has good stability and can be explored in various applications.