Novel bromoacetophenone-accelerated visible-light 3D and 4D printing methods for rapid fabrication of biocompatible and structurally dynamic scaffolds

Rapid and accurate visible-light photopolymerization is essential for advancing bioprinted engineered tissues. In this study, we developed a novel three-component photoinitiator system for visible light-induced crosslinking of gelatin methacryloyl (GelMA) hydrogels, designed to improve polymerization kinetics, mechanical strength, and structural integrity. Incorporation of 2-bromoacetophenone (BAP) considerably accelerated photopolymerization, with reaction rates increasing alongside BAP concentration, enabling the rapid fabrication of stable hydrogel scaffolds. Printing experiments confirmed that BAP promoted fast crosslinking of GelMA bioinks under visible light, reducing printing time while preserving high-resolution structural features. Additionally, the incorporation of BAP induced microscale structural transformations in the hydrogels during hydration, as evidenced by scanning electron microscopy imaging and swelling analyses. This unique property enabled the fabrication of multilayer constructs exhibiting time-dependent deformation, demonstrating four-dimensional (4D) printing capabilities. Moreover, biocompatibility evaluations revealed that cells maintained high viability in BAP-containing hydrogels. Overall, the BAP-based photoinitiator system offers a promising strategy for high-speed, high-resolution bioprinting, combining enhanced mechanical performance, reduced fabrication time, and dynamic structural adaptability—features that make it highly suitable for advanced biofabrication and tissue engineering applications.