Nanoencapsulation of natural extracts for improving antibacterial activity against oral bacteria

Abstract

The aim of this study was to improve antibacterial activity of natural extracts using nanoencapsulation. Chitosan (CS) and carrageenan (CR) were selected as the coating material to provide mucoadhesive properties to the nanoparticles (NPs). After six natural extracts of grapefruit seed extract (GSE), clove oil, thyme oil, cinnamon oil, black pepper oil, and ginger oil were nanoencapsulated using ionic gelation method, the effect of nanoencapsulation on their antibacterial activities was evaluated. Only four natural extract-loaded NPs were homogeneous and ranged 170-590 nm. The result of minimum inhibitory concentration (MIC) test showed that GSE possessed significant antimicrobial activity in both free and NPs among the six natural extracts. After fractional inhibitory concentration (FIC) test was performed in combination of GSE and the other five natural extracts, GSE, clove oil, and cinnamon oil were selected and tested, via time-kill study. The synergistic effects were observed in both GSE/clove oil and GSE/cinnamon oil combinations, and the antibacterial activity of GSE/cinnamon oil combination was increased by nanoencapsulation against both S. mutans and S. sobrinus. The result of mouth rinse test also indicated that both GSE/cinnamon oil free and NPs inhibited the growth of salivary S. mutans after mouth rinse, but significant reduction was observed in subjects using NPs compared to free combination. Finally, antimicrobial activities of GSE/cinnamon oil NPs in drinking yogurt were demonstrated. The result revealed that GSE/cinnamon oil NPs were able to more effectively inhibit the growth of oral bacteria than free combination in food products. This study suggested the potential of GSE/cinnamon oil NPs as a natural antimicrobial for oral health.