Tailoring of agarose hydrogel to modulate its 3D bioprintability and mechanical properties for stem cell mediated bone tissue engineering

Abstract

The intense gelling characteristics and viscosity constraints of agarose limit its utility as a sole ink material in 3D printing. This study presents the development of agarose bioink designed for cell-laden printing, featuring controlled printability, exceptional stiffness, and cell-responsiveness achieved via the insertion of photochemically reactive methacrylate groups. This chemical modification transforms the dense agarose network into a thinner structure, effecting a gentle thermogelling property that enhances the printability and facile cell encapsulation. Herein we examine the interplay between the degree of substitution and concentration variations to determine the optimal hydrogel composition. The best bioink composition possessed a lower shear modulus (storage modulus G' = 11.6 Pa) at 37 °C, assuring better bioprintability, while it possessed a Young's modulus of 1.4 ± 0.10 MPa in the crosslinked state, which is the highest reported in the natural single-matrix hydrogel systems. Studies with mesenchymal stem cells (MSC) confirmed that it is a good cell encapsulation matrix, achieving 111 % cell viability at 72 h. The bioprinted constructs promoted the osteogenic differentiation of MSC, as evidenced by mineralization and secretion of bone-related matrix. The gene expression analysis indicated that osteogenic marker expressions exhibited at least a two-fold increase on day 14 relative to the control group.