Photothermal studies of modulating effect of photoactivated chlorin on interaction of blood cells with bacteria.

Background: Bactericidal application of photosensitizers (PS) is a new and promising area. Up to now the action of PS against bacteria was studied without regard to immunocompetent cells, doses of drugs and radiation being used usually are not safe for such cells and therefore there is still no efficient model for PS application.

Methods: Action of chlorin, a plant derived photosensitizer, on a system of interacting cells and microbes was studied. Cell monitoring was done with a photothermal microscopy method. The two bacteria used were gram-positive (S. aureus) and gram-negative (E. coli) in a mixture of basic blood cells and neutrophils. The latter were used to model phagocytosis as fast cell response reaction.

Results: The strongest bactericidal effect was found when the cells and photoactivated chlorin act together. Selective bactericidal regime of PS application which does not affect cell viability was demonstrated.

Conclusions: The results obtained suggest that this photosensitizer may enhance cell natural defense capabilities.