Effect of terahertz radiation on drug activity in bacterial cells

Abstract The biological effects of terahertz (THz) waves have been increasingly studied in recent years with the development of THz wave generation and detection technology. THz waves have been reported to change membrane permeability and induce conformational changes in protein molecules. Drugs action on cells involves membrane permeability, and we therefore investigated the effect of THz waves on the activity of the cytotoxic drug bleomycin on Escherichia coli. 0.46 THz radiation with an average power of 2.5 W/cm2, pulse duration of 10 ms, and a repetition frequency of several Hz was noncytotoxic to E. coli cells. However, 0.46 THz radiation enhanced the cytotoxic activity of bleomycin in E. coli cells, and the drug-enhancing effect depended on the power density of the THz waves. The effect of THz radiation on drug uptake into cells was investigated based on the activity of the drug remaining in the culture medium after THz radiation or non-radiation. The activity of the drug remaining in the culture medium after THz radiation did not differ from that remaining after non-radiation. This indicates that THz radiation does not affect the bacterial cell-membrane permeability to bleomycin. Thus, this study suggests that 0.46 THz radiation enhances the cytotoxicity of bleomycin towards E. coli cells and may influence the mechanism of bleomycin action within cells rather than affecting drug uptake.