In Vitro Cytotoxicity of Stealth Liposomes Co-encapsulating Doxorubicin and Verapamil on Doxorubicin-Resistant Tumor Cells

Multidrug resistance (MDR) is a major obstacle to successful clinical cancer chemotherapy. A novel doxorubicin anti-resistant Stealth liposomes (DARSLs), prepared by co-encapsulating doxorubicin (DOX) and verapamil (VER) into stealth liposomes, has been developed. The average particle size of DARSLs was 118.1±22.3 nm. Encapsulation efficiencies of DOX and VER in DARSLs were greater than 95% and 70%, respectively. The IC50 of DARSLs as measured by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl tetrazolium bromide (MTT) assay in multidrug resistant rat prostate cancer Mat-LyLu-B2 (MLLB2) cells was 0.079±0.017 μM, 13 fold less than that for liposomal DOX with free VER (LDFV 0.96±0.46 μM) but only about 2 times less than FDFV. The IC50 cytotoxicity on MLLB2 cells of the various formulations was as follows: DARSLs∼LDLV