Microcalorimetric and microscopic studies on the inhibitory activities of methylene blue/TiO2 nanocomposites on Staphylococcus aureus and the mechanism of cell damage

The effect of methylene blue/TiO2 nanocomposites on Staphylococcus aureus was evaluated by a LKB-2277 Bioactivity Monitor at 37.0 °C. By analyzing the thermogenic power–time curves, kinetic parameters such as the growth rate constant (k), the maximum heat power of growth phase (Pm), generation time (tG) and the inhibitory ratio (I) were determined. The k and Pm decrease while tG and I increases with increasing concentrations of the methylene blue/TiO2 nanocomposites added into the microbe suspension. Both k and I have linear correlations with the concentration of the methylene blue/TiO2 nanocomposites. The effect of the methylene blue sensitized-TiO2 nanocomposites on the cell damage of S. aureus was investigated by microscopic method.