Structural and mechanical characteristics of silk fibroin and chitosan blend scaffolds for tissue regeneration

The expanding field of tissue engineering has required the necessity of developing biomaterials that are tissue compatible, biodegradable, and comparable in mechanical properties to that of native tissue. We propose that the blending of two natural polymers, silk fibroin (SF) and chitosan (CS), into a 3D scaffold will provide unique chemical, structural, and mechanical properties that can be utilized for in vivo tissue regeneration. SF is an attractive material for biomedical applications because it is a fibrous protein that has high permeability to oxygen and water, relatively low thrombogenicity, low inflammatory response, protease susceptibility, supports cell adhesion and growth, and, foremost, high tensile strength with flexibility. CS is a crystalline polysaccharide, with structure similar to glycosaminoglycans, that has good wound healing properties, is nontoxic, and has minimal foreign body reactions. We hypothesized that increasing the SF-to-CS ratio would increase the ultimate tensile strength and elastic modulus and decrease the water capacity of the SFCS scaffolds. With increasing content of silk fibroin, it is observed that the ultimate tensile strength and elastic modulus increase significantly. The ultimate tensile strength and the elastic modulus were significantly higher in the short axis direction for 25:75 and 50:50 SFCS blends as compared to the long axis (p < 0.05), while they were similar for the 75:25 SFCS blend. However, no differences were observed in the strain at failure among blends or due to directionality of applied strain. Increasing the chitosan content resulted in an increased water capacity of SFCS blends.