Evaluation of anti-biofilm effect of antimicrobial sonodynamic therapy-based periodontal ligament stem cell-derived exosome-loaded kojic acid on biofilm.

Antimicrobial sonodynamic therapy (aSDT) is an approach that uses ultrasound waves (UWs) and a sonosensitizer to generate reactive oxygen species (ROS) to damage microbial cells in biofilms. Using nano-carriers, such as exosomes (Exos), to deliver the sonosensitizer can potentially enhance the effectiveness of aSDT. aSDT can downregulate the expression of and genes, increasing the production of endogenous ROS and degradation of pre-formed biofilms. This study investigated the anti-biofilm effect of aSDT-based periodontal ligament stem cell-derived exosome-loaded kojic acid (KA@PDL-Exo) on pre-formed biofilms in root canals. Following the isolation and characterization of PDL-Exo, KA@PDL-Exo was prepared and confirmed. The minimal biofilm inhibitory concentration (MBIC) of KA, PDL-Exo, KA@PDL-Exo and sodium hypochlorite (NaOCl) was determined, and their anti-biofilm effects were assessed with and without UWs. The binding affinity of KA with GelE and SprE proteins was evaluated using molecular docking. Additionally, the study measured the generation of endogenous ROS and evaluated changes in the gene expression levels of and . The results revealed a dose-dependent decrease in the viability of cells within biofilms. KA@PDL-Exo was the most effective, with an MBIC of 62.5 µg ml, while NaOCl, KA and PDL-Exo had MBIC values of 125, 250 and 500 µg ml, respectively. The use of KA@PDL-Exo-mediated aSDT resulted in a significant reduction of the biofilm (3.22±0.36 log c.f.u. ml; <0.05). The molecular docking analysis revealed docking scores of -5.3 and -5.2 kcal mol for GelE-KA an SprE-KA, respectively. The findings observed the most significant reduction in gene expression of and in the KA@PDL-Exo group, with a decrease of 7.9- and 9.3-fold, respectively, compared to the control group (<0.05). The KA@PDL-Exo-mediated aSDT was able to significantly reduce the load in pre-formed biofilms, decrease the expression of and mRNA, and increase the generation of endogenous ROS. These findings imply that KA@PDL-Exo-mediated aSDT could be a promising anti-biofilm strategy that requires additional and investigations.