The Inhibitory Effects of Ficin on <i>Streptococcus mutans</i> Biofilm Formation

Abstract

To investigate the effects of ficin on biofilm formation of conditionally cariogenic <i>Streptococcus mutans</i> (<i>S. mutans</i>). Biomass and metabolic activity of biofilm were assessed using crystal violet assay, colony-forming unit (CFU) counting, and MTT assay. Extracellular polysaccharide (EPS) synthesis was displayed by SEM imaging, bacteria/EPS staining, and anthrone method while acid production was revealed by lactic acid assay. Growth curve and live/dead bacterial staining were conducted to monitor bacterial growth state in both planktonic and biofilm form. Total protein and extracellular proteins of <i>S. mutans</i> biofilm were analyzed by protein/bacterial staining and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), severally. qRT-PCR was conducted to detect acid production, acid tolerance, and biofilm formation associated genes. Crystal violet assay, CFU counting, and MTT assay showed that the suppression effect of ficin on <i>S. mutans</i> biofilm formation was concentration dependent. 4 mg/mL ficin had significant inhibitory effect on <i>S. mutans</i> biofilm formation including biomass, metabolic activity, EPS synthesis, and lactic acid production (<i>p</i> < 0.05). The growth curves from 0 mg/mL to 4 mg/mL ficin were aligned with each other. There was no significant difference among different ficin groups in terms of live/dead bacterial staining result (<i>p</i> > 0.05). Protein/bacterial staining outcome indicated that ficin inhibit both total protein and biofilm formation during the biofilm development. There were more relatively small molecular weight protein bands in extracellular proteins of 4 mg/mL ficin group when compared with the control. Generally, ficin could inhibit biofilm formation and reduce cariogenic virulence of <i>S. mutans</i> effectively in vitro; thus, it could be a potential anticaries agent.