Induction of lethal photosensitization in biofilms using a confocal scanning laser as the excitation source

Abstract

Objectives. To induce lethal photosensitisation in biofilms of Streptococcus pyogenes by using the scanning laser in a confocal microscope to photoactivate Sn (IV) chlorin e6 (SnCe6) whilst simultaneously measuring changes in cell vitality using fluorescent indicators of membrane integrity. Methods. Biofilms of S. pyogenes were immersed in a solution of 50 mg/L (70.28μM) SnCe6 and scanned with the 488 nm argon and 543 nm HeNe lasers in a confocal microscope. Changes in membrane permeability were quantified using image analysis tools. Results. Cell permeability increased in biofilms of S. pyogenes after successive scanning / exposure cycles in the presence of SnCe6. Conclusions. Cell death was induced in biofilms of S. pyogenes by the photosensitiser SnCe6 on exposure to the scanning laser emissions of a confocal microscope. The simultaneous recording of cell death demonstrates the real-time evaluation of a light-activated antimicrobial compound against biofilm.