Abstract
3D bioprinting has emerged as a promising technology in tissue engineering, allowing for the precise fabrication of complex structures to mimic native tissues. Coaxial bioprinting enhances the complexity of printed structures by extruding multiple materials in concentric layers. However, costly commercial systems and a lack of Do-it-Yourself (DIY) guides for coaxial 3D bioprinting limit the wider adoption of this technology. This study presents a detailed description of modifying a commercial 3D printer to a coaxial 3D bioprinting system that simultaneously drives two syringe pump extruders connected to a coaxial nozzle. The system was validated using a soft alginate-gelatin hydrogel core and a load-bearing methylcellulose-based (MC) hydrogel shell. Shape fidelity of the 3D printed structures was evaluated for core-shell extrusion ratio, coaxial nozzle configuration, and in-situ crosslinking of the hydrogel core. Employing optimized printing settings allowed the fabrication of complex scaffold structures with a gradual transition between the extrusion of core and shell material. Mesenchymal stem cells (MSCs) encapsulated in varying alginate concentrations were printed, maintaining shape fidelity and high cell viability. In conclusion, we developed a cost-effective DIY coaxial 3D bioprinter capable of extruding soft cell-laden hydrogels that are not printable by conventional extrusion bioprinting. This printer presents an easy to build and modify platform to encourage a wider audience to utilize and tailor coaxial bioprinting for their specific requirements.