Evaluation of Bacterial Viability in Photocrosslinked Hydrogels: Effects of Photoinitiator and UV Exposure on E. coli

Abstract

The development of targeted delivery systems has significantly enhanced modern therapeutic approaches, particularly in the administration of live biotherapeutics such as probiotics. Hydrogels have emerged as effective carriers for microbial encapsulation due to their biocompatibility, customizable structures, and ability to protect living cells in challenging physiological environments. This study investigates the application of a photopolymerizable hydrogel system, incorporating a photoinitiator, to encapsulate Escherichia coli and examines bacterial viability following UV-induced crosslinking. Two experimental models were utilized: (1) a hydrogel-based encapsulation method wherein E. coli cells were mixed with a hydrogel precursor solution, shaped into pellets, and subsequently exposed to UV light at 365 nm for crosslinking; and (2) a suspension-based assay in which the cells were directly exposed to varying concentrations of photoinitiator and UV light in the absence of hydrogel, facilitating the assessment of phototoxic effects. Bacterial viability and release were quantified through time-point sampling, serial dilution, and colony-forming unit (CFU) analysis. The results indicated that both photoinitiator concentration and UV exposure significantly impact bacterial survival. Although the hydrogel encapsulation offered partial protection, elevated photoinitiator concentrations and extended UV exposure resulted in decreased CFU recovery across both experimental models. This research provide important insights into optimizing photopolymerization parameters for engineered living materials and suggest conditions under which bacterial viability can be preserved during material fabrication. The data obtained from this study can inform the design of probiotic delivery systems and bioactive hydrogel platforms for biomedical applications.