Dual-photosensitizer polylactic acid filaments for 3D-printed photodynamic antimicrobial materials

3D-printed photodynamic materials offer a route to fabricate light-activated antimicrobial objects, but their performance depends strongly on photosensitizer (PS) retention, accessibility, and photophysical behavior after thermal processing. Here, rose bengal (RB) and zinc(II) phthalocyanine (ZnPc) were incorporated into polylactic acid (PLA) at 0.5% (w/w) and processed by melt extrusion and three-dimensional printing. The characteristic absorption and fluorescence emission bands of both chromophores were retained after processing, and the dual formulation provided complementary absorption in the green and red regions of the visible spectrum. RB release from the dual-PS material followed biexponential kinetics, with k_fast = 1.39 ± 0.29 min^-1 and k_slow = 0.013 ± 0.004 min^-1. Under white-light irradiation, RB-containing materials produced approximately 5-6 log reductions (>99.999%) in bacterial viability, with Bacillus subtilis inactivated more rapidly than Escherichia coli. ZnPc-containing PLA alone produced only partial inactivation, and no appreciable dark toxicity was observed. These results identify PS accessibility as a critical parameter governing the performance of melt-processed photodynamic materials.