Silver Nanoparticles Synthesized From Centella asiatica Extract and Asiatic Acid for Enhanced Biofilm Eradication of Streptococcus Associated With Oral Diseases.

Abstract

The biofilm-forming ability of Streptococcus species, particularly Streptococcus mutans, is a key factor in the pathogenesis of dental caries and periodontitis. Current treatments often exhibit limitations such as incomplete biofilm eradication and cytotoxicity to host tissues, highlighting the need for innovative and biocompatible therapeutic approaches. Therefore, this study aimed to investigate the potential of Centella asiatica ethanolic extract, its bioactive triterpenoids (asiatic acid and madecassic acid), and silver nanoparticles (AgNPs) synthesized from the extract as an alternative strategy for targeting S. mutans biofilms. The antibacterial and antibiofilm activities of the synthesized AgNPs against Streptococcus species were evaluated, alongside cytotoxicity assessments on human gingival fibroblast (HGF-1) cells using the MTT assay. The synthesized AgNPs exhibited superior antimicrobial efficacy compared to the extract, with significantly lower minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values (62.5/125 µg/mL) against S. mutans ATCC 25175 and S. mitis ATCC 49456, highlighting their potent bactericidal activity. Moreover, the AgNPs achieved rapid biofilm disruption, reducing biofilm biomass by 76% within 12 h at 1/2 × MIC, significantly outperforming the extract and triterpenoids. Scanning electron microscopy further revealed substantial extracellular polymeric substance degradation and biofilm structural disruption upon AgNP treatment, confirming their pronounced antibiofilm efficacy. In addition, the synthesized AgNPs demonstrated favorable biocompatibility, maintaining 68% cell viability in dental fibroblast cells, suggesting an optimal balance between antimicrobial potency and cytotoxicity. The synergistic interaction between AgNPs and C. asiatica phytochemicals significantly enhanced biofilm disruption compared to nonfunctionalized AgNPs. These findings underscore the potential of C. asiatica-based AgNPs as a novel, plant-derived nanotechnological approach for managing oral infections caused by biofilm-forming Streptococcus species. This study not only contributes to the development of alternative antibiofilm strategies but also paves the way for future clinical applications in oral healthcare.