Enhancement of mechano-structural characteristics of silk fibroin using microwave assisted degumming

The dielectric properties of silk coupled with the selective heating nature of microwaves have been employed in this work for the extirpation of gummy sericin layer from the surface of silk fibroin (S.F.). We studied the physicomechanical properties of intermittent microwave degummed silk fibers (MWS) systematically in comparison with the traditional sodium carbonate method. The experimental results validated the effective removal of sericin layer, with a degumming ratio of 25.5% on microwave irradiation, accounting to the breakage of disulfide bonds, on explosion of hot spots generated by the entrapped water molecules. The segmental motion and conformational reorientation of polymeric chains on administering microwaves, further improved the crystallinity of material, causing augmentation in Young's modulus and ultimate tensile strength of degummed silk by 115.4% and 268.8%, respectively, in comparison with the sodium carbonate degummed silk (DGS). The in-situ biodegradation studies verified the degradability of the material with 21.9% weight loss within 30 days following first-order kinetics (R² = 0.998) owing to the attack of proteolytic enzymes on the amino acid units of S.F., mitigating the concerns of waste generation.