Effect of Colloidal Platinum Nanoparticles on Streptococcus Mutans

Objectives: This study evaluated the effect of colloidal platinum nanoparticles (CPN) on the viability of Streptococcus mutans (S. mutans).
Methods: Three different of colloidal platinum nanoparticles were divided into four groups: control group (sterile water), PAA-Pt group (1.16% polyacrylic acid, 0.02% platinum, and 98.82% water), C-Pt group (0.02% platinum, 0.29% sodium citric acid, and 99.69% water), C-CyD-Pt group (0.3% cyclodextrin, 0.02% platinum, and 99.68% water). S. mutans was cultured in an anaerobic condition for 24 h, then adjusted in Brain Heart Infusion (BHI) broth to 10⁷ cells/ml based on its optical density. The bacterial suspension was incubated with four groups in various concentrations (40% ~90%) respectively at 37 degree centigrade for 24 h in an anaerobic condition. Time course of the effects of CPN on bacterial growth was also examined up to 6 h. Dilution series (10^-1~10^-6) were made using BHI broth for all samples, and a 100 μ L suspension of each dilution was applied to BHI agar plate. After incubation for 24 h in an anaerobic condition, the colony-forming units (CFU/ml) were determined.
Results: As the concentration increases, it was found that S. mutans was susceptible to the three kinds of CPN, among which PAA-Pt group exhibited the lowest minimal inhibitory concentrations, ranging from 40% to 90%.
Conclusions: CPN has a remarkable bactericidal effect on S. mutans. This result indicates that CPN may be a candidate antibacterial agent for incorporation into dental restorative materials.