Green Synthesis: Antimicrobial Activity on Streptococcus mutans Biofilm

Objectives: Plant-mediated synthesis of nanoparticles is a green chemistry approach that connects nanotechnology with plants without the use of reagents and toxic solvents to humans. This study evaluated the antimicrobial activity, minimum inhibitory concentration, minimum bactericidal concentration of the plant extract of Syzygium cumini and silver nanoparticles synthesized with plant extract, on Streptococcus mutans biofilm.
Methods: From the leaves of S. cumini, samples of the plant extract were obtained and for the synthesis of the nanoparticles, silver nitrate was added. To evaluate the antimicrobial activity, the agar diffusion test was used. Biofilms of S. mutans (ATCC 25175) were grown in microtiter plates, using Brain Heart Infusion culture media for 48h at 37°C. The nanoparticles were then added in different concentrations: 100%, 6.25% and 1.5%. Chlorhexidine 0.12% was used as a positive control. Cell viability analysis was performed by the XTT method and the morphological characteristics of the nanoparticles were performed by Scanning Electron Microscopy and Zeta Potential. To evaluate cytotoxicity, human keratinocyte cell line (NOK) grown in Dulbecco Mem / Ham F-12 culture medium, 10% fetal bovine serum and 1% penicillin, streptomycin and glutamine were used. Cell metabolism was analyzed by the alamarBlue® test.
Results: The evaluation of the results showed that the nanoparticles synthesized presented different sizes and geometric shapes, with an average size of 80 nm. The extract and the synthesized nanoparticles showed antimicrobial activity for S. mutans.
Conclusions: It was concluded that the plant extract and silver nanoparticles (green synthesis) may be an alternative for the control of S. mutans biofilm.