Photoinitiator-dependent network restructuring in hydrogels: a mechanical, functional and biological comparison

Photopolymerizable hydrogels represent a versatile class of biomaterials with tunable mechanical, structural, and biological properties. However, a comprehensive understanding of how different photoinitiators (PIs) dictate hydrogel performance remains limited. In this study, representative Type I (Irgacure 184, Irgacure 2959, TPO, LAP) and Type II (Eosin Y) PIs were systematically evaluated under identical formulation to elucidate their influence on gelation kinetics, network architecture, and cytocompatibility. Rheological, swelling, and mechanical analyses revealed that Type I initiators facilitated rapid gelation and produced highly crosslinked networks with elevated storage moduli and reduced swelling ratios. Among these, Irgacure 184 achieved the most favorable balance between stiffness and biocompatibility, whereas TPO generated the densest and stiffest networks. Conversely, the Type II Eosin Y system formed more open and hydrophilic architectures but exhibited reduced mechanical robustness due to its visible‐light initiation mechanism. LAP and Irgacure 2959 demonstrated intermediate behavior, yielding moderately crosslinked, diffusion‐permeable networks that supported improved cytocompatibility. Collectively, these findings highlight that PI chemistry fundamentally governs radical generation efficiency, network development, and cellular response. The mechanistic insights presented here provide a rational basis for designing photocrosslinkable hydrogels with precisely tailored structural integrity and biological performance for next‐generation biofunctional materials.