Accelerated desalting and purification of silk fibroin in a <scp>CaCl₂‐EtOH‐H₂O</scp> ternary system by excess isopropanol extraction

Abstract

Abstract BACKGROUND Silk fibroin has attracted extensive attention due to its useful biological properties. However, in the regeneration process of silk fibroin, the need for highly concentrated neutral salt dissolution and long‐term dialysis greatly hinder the development of silk biomaterials. RESULTS A 3‐fold volume of isopropanol (IP) was added to one volume of 20% (w/v) silk fibroin solution dissolved in a CaCl 2 ‐EtOH‐H 2 O ternary system (SFTS) to extract the protein. The extraction resulted in the precipitate consisted of aggregated silk fibroin in the SFTS. The extracted protein was easily resolubilised in water. Compared with the original dialysis time required for the SFTS, the dialysis time of the extracted protein was shortened by nearly half. When the SFTS was diluted with a 2.5‐fold volume of water, the same IP extraction resulted in the dialysis time being shortened by two thirds. SDS‐PAGE showed that IP extraction did not cause breakage of the silk peptide chain. FTIR and X‐ray diffraction indicated this extraction had no influence on the secondary structure of silk fibroin. CONCLUSION Excess IP extraction effectively accelerates the desalting and purification of fibroin in a CaCl 2 ‐EtOH‐H 2 O ternary system without affecting the protein structure, thus greatly improving the regeneration efficiency of silk fibroin. © 2020 Society of Chemical Industry