Antibacterial activity of silver nanoparticles-Clinacanthus nutans (AgNP-CN) against Streptococcus mutans

Clinacanthus nutans was found to possess anti-venom, anti-inflammatory, analgesic, anti- diabetic, anti-rheumatism, antiviral and antioxidant properties. Silver nanoparticles are nanoparticles between 1nm to 100nm in size and play significant role in medicinal fields. Silver nanoparticles exhibit unique properties, such as excellent conductivity, chemical stability, catalytic and antimicrobial activity. Streptococcus mutans is usually discovered in human oral cavity and the main aetiological of tooth decay. There is no study on antibacterial effect of silver nanoparticles Clinacanthus nutans (AgNP-CN) against Streptococcus mutans reported to date. Therefore, objective of this study is to investigate antibacterial properties of silver nanoparticles Clinacanthus nutans against Streptococcus mutans. Streptococcus mutans was subcultured in brain heart infusion (BHI) broth and agar. AgNP-CN with different concentrations was tested against Streptococcus mutans via disc diffusion assay, minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC). Amoxicillin was used as positive control while DMSO and blank silver nanoparticles were used as negative control. Disc diffusion assay shows AgNP-CN inhibit Streptococcus mutans growth. AgNP-CN shows the greatest inhibition properties (15.3±1.53 mm) in comparison to Clinacanthus nutans leaves extract (6.0±0.01 mm) and blank silver nanoparticles (6.0±0.01 mm). MIC value for AgNP-CN is 2.5±0.01 mg/mL while amoxicillin is 0.007±0.01 mg/mL. Whereas MBC values for AgNP-CN is 2.5 mg/mL. Results are concentration dependent, with higher concentration shows better inhibition property. It can be concluded AgNP-CN possesses bactericidal properties against Streptococcus mutans.