Selenium Nanoparticle Enhanced Photodynamic Therapy against Biofilm forming Streptococcus mutans

Abstract

Present work explores the novel selenium nanoparticle-enhanced photodynamic therapy of toluidine blue O against Streptococcus mutans biofilm. Physiochemical (Ultraviolet-visible absorption, FTIR, and fluorescence spectroscopy) and Electron microscopy techniques were used to characterize selenium nanoparticles. The UV spectrum of different concentrations of SeNP were showed distinct peak at ~288 nm, which confirmed the successful synthesis of SeNP in this study. The synthesized Selenium nanoparticles were uniform and spherical in shape with average size ~100 nm. In FTIR spectra of SeNPs there were strong absorption band around 3425cm, 2928 cm and 1647 cm. TBO showed MIC and MBC of 62.5 μg/mL and 125 μg/mL respectively whereas in presence of SeNPs showed MIC and MBC of 31.25 μg/mL and MBC of 62.5 μg/mL. SeNPs–TBO conjugate showed twofold higher activities against S mutans than TBO alone. A 630 nm diode laser was applied for activation of SeNPToluidine blue O (TBO) combination and TBO against S. mutans biofilm and cells. The UV-vis absorption result suggests that TBO is not present on the surface of SeNP. In fluorescence emission spectra, there is enhancement of fluorescence of TBO fluorescence in the presence of nanoparticle. This showed that SeNP are enhancing the photodynamic therapy. Antibiofilm assays and microscopic studies showed significant reduction of biofilm presence of conjugate. A crystal violet assay revealed a maximum percent inhibition of S. mutans biofilm formation after 24 hours’ incubation, recorded as 20% and 60% by TBO (31.25 μg/mL) and SeNP–TBO (31.25 μg/mL; TBO) conjugate, respectively. XTT biofilm reduction assay were showed 32% loss in viability in presence of SeNP-TBO conjugate whereas in presence of only TBO there was 22% loss in viability of cells. Fluorescence spectroscopic study confirmed type I photo toxicity against biofilm. Selenium nanoparticle conjugate–mediated photodynamic therapy may be used against recalcitrant biofilm based infections and can be helpful in dentistry. Key-wordsS. mutans, SeNP, TBO, UV absorption, FTIR, fluorescence spectroscopy INTRODUCTION Microorganisms have traditionally been considered as planktonic, freely suspended cells. However in their natural environment bacteria forms biofilm communities which are sessile organisms embedded in hydrated extracellular polymeric matrix. [1] Biofilms are spatially structured heteromorphic microbial communities ensconced in exopolymeric matrix material. It has been shown that a substantial amount of microbial infections occur through biofilm formation. The formation of biofilm is a dynamic process. In process of biofilm formation the bacteria undergo a coordinated series of molecular events in response to the environmental signals that leads to the Access this article online Quick Response Code Website: