Superior performance of macroporous over gel type polystyrene as a support for the development of photo-bactericidal materials.

A hexanuclear molybdenum cluster [MoIAc] (1) has been ionically bound onto macroporous (P) and gel-type (P) resins and their performance as materials for the photodynamic inactivation of microorganisms has been studied. It has been found that 1@P in combination with light is able to reduce 99.999999% of the population of Gram-positive Staphylococcus aureus whereas the activity of 1@P is limited to a 99.99% reduction at the same light dose. The same trend is observed with Gram-negative Pseudomonas aeruginosa. A comprehensive study of both materials has been performed using confocal laser scanning microscopy, thermogravimetric analysis, nitrogen porosimetry, steady state and time resolved fluorometries and diffuse reflectance spectroscopy. The photochemical generation of singlet oxygen (O) has been assessed using 9,10-dimethylanthracene as a trap for this reactive oxygen species. It can be concluded that the nature of the polymeric support is of paramount importance for the development of surfaces with bactericidal properties.