3D coaxial bioprinting of RADA16-I self-assembling peptide hydrogel.

Peptides that self-assemble into hydrogels provide a dynamic microenvironment for various cell types. Combining top-down extrusion 3D bioprinting with bottom-up self-assembly of peptide hydrogels offers an innovative approach to biofabrication. However, modest mechanical properties of peptide hydrogels pose challenges for extrusion 3D bioprinting. This study introduces RADA16-I peptide hydrogels for bioprinting by leveraging the potential of coaxial extrusion to print mechanically soft hydrogels. A coaxial 3D bioprinter was employed to co-extrude a RADA16-I peptide core supplemented with methylcellulose (MC) and sucrose, surrounded by an MC-alginate composite hydrogel shell. The phosphate-buffered MC-alginate shell provides stability and initiates the RADA16-I hydrogel self-assembly post-extrusion. Rheological characterization confirmed the increase in viscosity of the RADA16-I core solution without compromising self-assembly (G' ≈ 100 Pa). Core extrusion ratio was set to 20% to balance filament stability and soft-core content. Printed scaffolds maintained excellent shape fidelity and structural integrity over a 21-day culture period, with gradual MC release (≈90%) creating an open-porous shell structure. Mesenchymal stem cells (MSCs) encapsulated in the RADA-MC core hydrogel tended to aggregate, forming a dense collagen network with calcium phosphate deposition. Bioprinted cell-laden scaffolds displayed a homogeneous distribution of viable cells (>90%). In conclusion, this approach successfully introduced self-assembling peptide hydrogels to bioprinting technology, offering a promising strategy for biofabrication.