Biocompatible Hydrogel Microspheres Based on Modified Silk Fibroin and Gelatin for Injectable 3D Bone Tissue Scaffolds

Currently investigated two-dimensional cell culture systems are typically inadequate for large-scale cell expansion and prone to causing altered cell morphology, aberrant differentiation, and distorted protein expression. To overcome these limitations, a glycidyl methacrylate-modified silk fibroin (SFMA)/methacrylic anhydride-modified gelatin (GelMA) interpenetrating polymer network hydrogel (SFMA-GelMA) was developed via microfluidic fabrication for three-dimensional (3D) bone tissue engineering applications. With increased SFMA content, the molecular chains in SFMA-GelMA undergo a structural transformation from random coil to β-sheet and β-crystallite, enhancing storage modulus to about 500 Pa and extending degradation duration from about 47.7% to 84.3% mass retention over 7 days. The higher GelMA content with the arginine-glycine-aspartic acid sequence in SFMA-GelMA facilitated early cell adhesion, provided interconnected pores (5-80 μm diameter), and promoted the osteogenic differentiation of MC3T3-E1preosteoblasts in 3D culture, as confirmed by alkaline phosphatase activity up to about 45 U/mg protein. Overall, SFMA-GelMA shows substantial potential as a 3D cell culture scaffold and injectable material for regenerative medicine, particularly in bone tissue engineering.