The post-processing temperature or humidity can importantly control the secondary structure and characteristics of silk fibroin films

Temperature and humidity (TH) are highly important factors that can control the secondary structure and characterization of silk fibroin (SF) biomaterials. In this study, the water stability, secondary structure, mechanical properties, surface morphology, and degradation of silk fibroin films (SFFs) with post-processing in different TH were investigated. Fourier transform infrared indicated that the SFF secondary structure did not change under low-relative humidity (RH) despite temperatures up to 180 degrees C, while it transformed at 40 degrees C with 100% RH in 10 min. A film with a higher tensile strength (42.1 +/- 8.2 MPa) could be obtained after post-processing at 90 degrees C/100% RH for 10 min. While a film with higher ductility (elongation at break: 198.8 +/- 31.8%) was generated after post-processing at 40 degrees C/100% RH for 10 min. Scanning electron microscope showed that the film presented a network structure of nanoparticles in series under certain TH post-treatment. Enzymatic hydrolysis proved that the SFFs containing a higher content of silk II structure degraded more slowly. Therefore, TH post-treatment is a relatively mild way to change the secondary structure and properties of SFFs, which can be widely used in loading drugs and maintaining the activity of drugs in SF biomaterials.

Automated summary

Temperature and humidity play crucial roles in controlling the secondary structure and properties of silk fibroin biomaterials. Post-processing under different temperature and humidity conditions can alter the mechanical properties and morphology of silk fibroin films, making them suitable for drug delivery applications.