Optimizing Green Light Photoredox Catalyzed Polymerizations for 3D Printing of Cell-Laden Hydrogels.

3D bioprinting is a powerful tool for fabricating complex tissue-like constructs, with digital light processing (DLP) offering exceptional speed and precision. However, conventional DLP relies on harmful UV light, limiting its application for cell-laden structures. Here, we developed green light-reactive photosystems for high-resolution hydrogel 3D printing. A polyacrylamide-based formulation (Resin 1) with Eosin Y as a photoredox catalyst enabled rapid prototyping (<10 s/100 μm) with low-intensity green light, achieving ∼50 μm resolution in structures such as vessel models with up to 90 wt % water. To improve cytocompatibility, we introduced a methacrylated-gelatin formulation (Resin 2), followed by a system with Eosin Y, dithiothreitol, and norbornene-functionalized gelatin (NorGel, Resin 3). Resin 3 enabled DLP printing of cell-laden constructs encapsulating human dermal fibroblasts in a cylindrical geometry with ∼90% viability after 3 days. This green light DLP platform integrates high resolution, rapid processing, and cytocompatibility to advance fabrication of physiologically relevant tissue models.