Methylene blue sensitizes E. coli cells to X-rays

Methylene blue (MB) is shown to sensitize E. coli cells to the effects of X-rays. This sensitization is dependent on factors such as dye concentration, incubation temperature, membrane permeability, and repair capacities, suggesting that the binding and/or penetration of the dye into the cells determines the potentiation of the lethal effects of X-rays by MB. It is also demonstrated that the presence of the polymerase 1 enzyme is essential for this sensitization to take place. Since MB is known to penetrate, accumulate, and be retained preferentially in some malignant tissues, the possibility of using this dye as a specific sensitizer to X-rays in the radiotherapy of some cancers is discussed.