Preparation and in vitro characterization of remdesivir-loaded liposomes for inhalation

Remdesivir-loaded liposomes for inhalation were prepared and the in vitro properties were evaluated. Firstly, preparation methods of remdesivir-loaded liposomes were screened, and single-factor experiments were conducted to optimize the prescription and preparation process. Then the physical property, deposition ratio and aerodynamic particle size distribution of remdesivir-loaded liposomes suspension for inhalation were comprehensively evaluated. As a result, the optimal liposomes were prepared by the thin-film dispersion method with pH 6.5 phosphate-buffered saline as the hydration medium. In the prescription, the ratio of drug to DPPC was 1∶20; the cholesterol accounted for 10% of total lipids; and 20% DSPE-mPEG 2000 was added as stabilizer.4% trehalose was added as lyoprotectant when lyophilizing to obtain ideal appearance, good stability and a small particle size change after reconstitution. Remdesivir-loaded liposomes were spherical with smooth surface and uniform particle size distribution under transmission electron microscope. In vitro release tests showed no significant change for release curves of remdesivir-loaded liposomes suspension before and after nebulization. Deposition experiments indicated that the fine particles fraction of liposomes was 51.4%, and the mass median aerodynamic diameter was less than 5 μm measured by next generation impactor. To sum up, remdesivir-loaded liposomes for inhalation with high encapsulation efficiency and stability can achieve a suitable particle size distribution to effectively deposit in the lung after nebulization, which provides a new approach for the treatment of COVID-19.