Multi-network granular hydrogel with enhanced strength for 3D bioprinting

Granular hydrogels are a kind of bulk hydrogel that are densely assembled by microparticles, showing great potential in 3D bioprinting. To develop a granular hydrogel-based bioink with enhanced strength, the present study combined methacryloylated gelatin (GelMA) with granular hydrogel to fabricate a compound bioink. Poly (γ-glutamic acid) (PG) microspheres and hydroxy propyl chitosan (CSPO) microspheres were fabricated, respectively, and self-assembled via charge interaction between microspheres to form a granular hydrogel after adding GleMA solution. However, its assembly ability decreased with the increase of the content of CSPO microspheres. The composite granular hydrogel with same mass content of PG microspheres and CSPO microspheres showed superior storage modulus, shear-thinning and self-healing ability. The composite granular hydrogels carrying adiposed derived stem cells (ASCs) showed well-performed extrudability and fidelity. In addition, after printing, UV light was used for further cross-linking GelMA, forming multi-networks that significantly improve the strength of the printed engineered tissue. ASCs proliferated significantly in bioink. The composite granular hydrogel thus showed great potential as bioink with enhanced strength for cell printing.