Holmium therapy Controlled release from liposomes by HIFU

Abstract

Triggered release from liposomes has mainly been reported for hydrophilic compounds. Unfortunately, the largest group of anti-cancer therapies involve agents that are lipophilic. This study proposes a high-intensity focused ultrasound (HIFU)-triggered release system for both lipophilic and hydrophilic compounds from liposomes. Thus, a thermosensitive liposome formulation was prepared, characterized and subsequently exposed to HIFU at different acoustic powers and time durations. The liposome size was around 130 nm (PDI <0.02) and the Tm of both liposome formulations was around 42 ⁰C. Furthermore, a non-thermosensitive liposome was developed. The liposome size was around 100 nm (PDI <0.07) and no Tm was measured. After exposure of both liposome formulations to HIFU, an increase release was observed when the acoustic power or exposure duration was increased. Fluorescein had its highest release after 16 minutes at 80 W (90%). Nile Red showed 60% release after 16 minutes of exposure at 80 W. After HIFU exposure, the liposome characteristics were not affected. This study demonstrates ultrasound-triggered release of a substantial amount of lipophilic compounds from liposomes. The exact mechanism of this release requires further study. The flexibility of the acoustic power and exposure durations promises a controllable release. It shows great promise for future drug delivery systems.