Ultrasound responsive violacein loaded liposomes for sonodynamic therapy

Violacein is a bisindole compound with interesting anticancer and antimicrobial properties, but poor water solubility limiting its clinical application. The aim of this study was to evaluate the utility of free, and liposome-encapsulated violacein as a novel sonosensitizer for sonodynamic therapy (SDT) against melanoma cells and various strains of microorganisms. For this purpose, liposomes consisting of EggPC, cholesterol, and DOTAP were created. This approach enabled higher and more stable concentrations of violacein, enhancing its synergy with ultrasounds against melanoma cell lines MICH-2 (primary) and HTB-140 (metastatic). The combination of violacein and SDT resulted in a reduction of cell viability by over 90 %. A significant increase in oxidative stress was also observed in treated cells. In studies on a broad panel of microorganisms, the results were more variable, with activity strongly dependent on the specific strain. Notably, potent bactericidal and fungicidal effects were observed against Vibrio vulnificus and Candida auris in both planktonic and biofilm forms. Overall, our study provides evidence that violacein, and in particular liposomal form of this compound, when used in combination with ultrasounds, exerts strong anticancer and antimicrobial effects, which deserves further investigation.