A Multi-Crosslinkable Methacrylated Alginate-GelMa Bioink for Drop-on-Demand Bioprinting

To advance biofabrication, this work presents the development of a multi-crosslinkable bioink based on methacrylated alginate di-aldehyde (ADAMa) combined with gelatine methacryloyl (GelMa). ADAMa was synthesized using methacrylic anhydride under specific conditions, and successful functionalization as well as changes in chain length were confirmed by NMR (Nuclear Magnetic Resonance), ATR-FTIR (Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy), and GPC (Gel Permeation Chromatography) analyses. The resulting ADAMa-GelMa bioink can be crosslinked via several independent mechanisms, including UV-initiated photopolymerization, enzymatic crosslinking, Schiff-base formation, and ionic gelation with calcium ions. Our study confirms an increase in the compressive modulus with increasing GelMa content, ranging from 0.3 to 30 kPa, and in vitro biocompatibility for ADAMa-GelMa bioink with enhanced cell-material interaction for a 25:75 ADAMa-GelMa ratio. Furthermore, Drop-on-Demand (DoD) bioprinting performance was evaluated using filament fusion test and grid structure test analyses, along with structural fidelity assessment of free-standing pillar arrays, including metrics such as pillar height and spacing. Multiphoton microscopy further revealed homogeneous cell distribution within printed pillars. Overall, this system provides tuneable mechanical properties, high cell viability, and strong structural fidelity, making it a promising candidate for the fabrication of complex, cell-laden constructs in advanced biofabrication applications.