Enhancement of the Response to Ultrasound by Encapsulating Metal Nanoparticles in Liposomes

Drug delivery systems (DDSs) that selectively and efficiently deliver drugs to target sites can be made more effective by using ultrasound. However, ultrasound-based DDSs have the problem that the drug carriers often react to other stimuli besides ultrasound. Therefore, we propose liposomes encapsulating metal nanoparticles (e.g., tungsten particles) as carriers that respond only to ultrasound. In this study, liposomes and metal nanoparticle-encapsulated liposomes were prepared by an emulsion-based method, and the changes in brightness due to calcein release upon ultrasound irradiation were observed under a microscope. The results confirmed that the incorporation of & metal nanoparticles into the liposomes enhanced their response to ultrasound.