Photoactive Water-Soluble Vitamin K: A Novel Amphiphilic Photoinduced Antibacterial Agent

Menadione sodium bisulfite (MSB), also known as water-soluble vitamin K-3 widely used as an animal food additive due to its low toxicity and low cost, is for the first time proven to be photoactive and antibacterial under various photoirradiation sources, evidenced by a computational modeling method and well-designed experiments. MSB demonstrates its robust photoactivity and application potential under ultraviolet A (UVA, 315-400 nm) irradiation. The results reveal that MSB could effectively generate reactive oxygen species (ROS) under UVA irradiation due to the formation of its oxidative triplet excited state. The photoinduced antibacterial tests also demonstrate the nonselective bacterial inactivation functions of MSB under proper photoirradiation. MSB was challenged against Gram-negative Escherichia coli (E. coli) and Gram-positive Listeria innocua (L. innocua) under UVA irradiation and exhibited excellent antibacterial performance (99.999% bacterial inactivation in 30 min of UVA exposure) in PBS. The antibacterial performance of MSB does not decay after five times of repeated exposures to bacteria and UVA irradiation, indicating the photostability and durability of MSB as a photoinduced antibacterial agent. More interestingly, solvents played a significant role in photoinduced antibacterial properties but not in the generation of ROS of MSB, indicating that the solvents may serve as contact media between MSB and bacteria cells. Intimate contact of MSB and microorganisms is thought of as a determinant in the bacterial inactivation by ROS or triplet excited states due to their relatively short lifetime and limited diffusion and function radius.