Effects of Cryo-grinding on the Extraction and Physicochemical Properties of Silk Fibroin

Herein, cryo-grinding technique was introduced into the extraction process of silk fibroin, aiming to achieve efficient preparation and controllable performance of silk fibroin. More specifically, the cocoon was pre-frozen in liquid nitrogen for 12 h before being ground, and the physical and chemical properties of the obtained sample (GSF322) were compared with the control one (SF). Results revealed that, compared with SF, the degumming duration for GSF322 dwindled from 90 min to 40 min with a close yield. Circular dichroism analysis demonstrated that the pretreatment process would not destroy the steric structure of the macromolecule. Turbidity assay implied that the assembly activity of the polymer in vitro could also be manipulated via assorted grinding periods, among which the sample ground for 3 min had the best assembly capacity. Dissection of the Zeta potential displayed that, after grinding, the positively-charged groups on the molecular chain of GSF322 might multiply, resulting in the exposure of more -NH₂ groups in the surroundings and enhanced hydrophilicity of the material, which was in accordance with the trend from the water solubility experiment. Moreover, in the thermostability test, the dehydration peak for GSF322 was higher than that of SF, showing better thermal stability. To conclude, concerning the extraction process for silk fibroin, the cryogrinding approach sheds light on both the strengthening of the extraction efficiency as well as the tuning of the physiochemical aptitudes of the polymer.