Chitosan nanoparticles efficiently enhance the dispersibility, stability and selective antibacterial activity of insoluble isoflavonoids.

Natural isoflavonoids have attracted much attention in the treatment of oral bacterial infections and other diseases due to their excellent antibacterial activity and safety. However, their poor water solubility, instability and low bioavailability seriously limited the practical application. In this study, licoricidin-loaded chitosan nanoparticles (LC-CSNPs) were synthesized by self-assembly for improving the dispersion of licoricidin (LC) and strengthening antibacterial and anti-biofilm performance. Compared to free LC, the minimum inhibitory concentration of LC-CSNPs against Streptococcus mutans decreased >2-fold to 26 μg/mL, and LC-CSNPs could ablate 70 % biofilms at this concentration. The enhanced antibacterial activity was mainly attributed to the spontaneous surface adsorption of LC-CSNPs on cell membranes through electrostatic interactions. More valuably, LC-CSNPs had no inhibitory effect on the growth of probiotic. Mechanism study indicated that LC-CSNPs altered the transmembrane potential to cause bacterial cells in a hyperpolarized state, generating ROS to cause cells damage and eventually apoptosis. This work demonstrated that the chitosan-based nanoparticles have great potential in enhancing the dispersibility and antibacterial activity of insoluble isoflavonoids, offering a promising therapeutic strategy for oral infections.