**3. Biocompatibilty research of silk fibroin**

Silk fibroin has been utilized as natural biomaterial in tissue engineering applications. Many researches have been made in vitro to reveal its attractive properties such as slowcontrollable degradation, mechanical robustness, and inherent biocompatibility[18-21].

For the silk fibroin scaffolds are made up of proteins, those materials which have been implanted will degrade and could hardly be separated from host tissues, that made the study of histocompatibility difficult. Therefore, few report can be found about research on biocompatibility and degradation of porous fibroin scaffolds in vivo [4,22].
