Protein-in-polysaccharide bioink for 3D bioprinting of muscle mimetic tissue constructs to treat volumetric muscle loss.

Developing engineered skeletal muscle tissues with biomimetic structural and functional properties is required to treat volumetric muscle loss (VML) caused by injuries or surgical procedures. 3D bioprinting has emerged as a promising tool for fabricating muscle tissue constructs to restore or replace lost skeletal muscle tissue functions. Natural polymers are widely used as bioinks due to their ability to promote printability, biocompatibility, and cell functionalities. In the present study, a novel protein-in-polysaccharide bioink combination containing methylcellulose (MC), alginate (Alg), and gelatin (Gel) was used. In order to achieve maximum cell viability, the bioink was crosslinked using ionic or enzymatic crosslinking agents under physiological conditions. The concentration of MC-Gel combination was initially optimized to check the printability and stability. Further, Alg was added to the MC-Gel to improve the printability, and the effect of crosslinking conditions were optimized. The optimized conditions were used to bioprint skeletal muscle mimetic constructs with C2C12 cells, which showed excellent proliferation and differentiation. In vivo efficacy of the MC-Alg-Gel constructs showed better functional regeneration of skeletal muscle in VML injuries in mice model. Thus, the novel protein-in-polysaccharide bioink and crosslinking strategy holds significant potential to fabricate tissue constructs for skeletal muscle engineering.