The selectivity of chemotherapeutic agents for liver cancer is poor. When they kill tumour cells, they produce serious adverse reactions in the whole body and multidrug resistance (MDR) is also a major hurdle in liver cancer chemotherapy. Combination therapy is a useful method for overcoming MDR and reducing toxic and side effects. In this study, we developed a long-circulating codelivery system, in which doxorubicin (DOX) and schizandrin A (SchA) are combined against MCF-7/ADR cells. The DOX-SchA long-circulating liposome (DOX-SchA-Lip) was prepared using ammonium sulphate gradient method. The two drugs were co-encapsulated into the distearoyl phosphatidylethanolamine-polyethylene glycol (DSPE-mPEG2000) liposome and the liposome had an average particle size of (100 ± 3.5) nm and zeta electrical potential of (-31.3 ± 0.5) mV. The average encapsulation rate of DOX was 97.98% and that of SchA was 86.94%. DOX in liposome had good sustained-release effect. The results showed that DOX-SchA-Lip could significantly prolong the half-life (t1/2z) of the DOX and SchA, increase their circulation time in vivo, improve its bioavailability and reduce their side effects. Liposome can effectively induce early apoptosis of HepG2/ADR cells and the cell cycle was blocked in S-phase by DOX-SchA-Lip in a dose-dependent manner. The IC50 of compound liposome to HepG2 and HepG2/ADR were 0.55 μmol/L and 1.38 μmol/L, respectively, which could significantly reverse the resistance of HepG2/ADR and the reversion multiple was 30.28. It was verified that DOX-SchA-Lip can effectively kill tumour cells and reverse MDR.
Keywords: Multidrug resistance; combination therapy; doxorubicin; long-circulating liposomes; schizandrin A.