Photo-sensitive liposomes loading doxorubicin hydrochloride reverse drug resistance of breast cancer

This study was aimed to build a new photo-sensitive co-delivery liposomes which combine photodynamic therapy with chemotherapy to reverse drug resistance of breast cancer. Photodynamic photosen-sitizer chlorin e6 trimethyl ester (Ce6tM) and chemotherapeutic drug doxorubicin hydrochloride (DOX) were loaded into the liposomes (liposomes loaded with Ce6tM and DOX, CDL) by thin-film hydration extrusion and ammonium sulfate active loading methods. CDL was characterized with cryo-transmission electron microscopy (Cryo-TEM), dynamic light scattering particle size, zeta potentials and photo-sensitive DOX release behaviors in vitro. CDL cytotoxicity, singlet oxygen production, DOX accumulation, intracellular ATP level and cell cycle analysis in MCF7/ADR cells were evaluated. Finally, the tissue distribution of DOX and antitumor effects of CDL in BALB/c-nu nude mice bearing MCF7/ADR tumor were investigated. The results showed that the particle size of obtained CDL was 90.7 ± 1.1 nm and distributed uniformly. CDL possessed outstanding properties of photo-sensitive drug release profile. The accumulated release of DOX reached (96.52 ± 0.11)% in 2 min under 671 nm laser irradiation (2 W·cm^-2). Interestingly, DOX in CDL could maintain rapid release after 671 nm laser irradiation with low power and short time (15 s, 0.25 W·cm^-2). This phenomenon was caused by oxidation of unsaturated phospholipids in CDL under 671 nm laser irradiation and had nothing to do with the slightly elevated temperature. Photo-sensitive drug release behavior contributed to increased DOX accumulation in MCF7/ADR cells. The half inhibition concentration (IC₅₀) of DOX in CDL laser group in MCF7/ADR cells was decreased by 601.9-fold compared with no laser group, which could be related to increased accumulation of DOX, decreased ATP levels and cell cycle arrest in MCF7/ADR cells. With the help of CDL, DOX accumulation in tumor was increased and in cardiac toxicity was reduced in vivo. CDL laser group showed a good anti-tumor effect. The tumor inhibition rate was (94.7 ± 6.2)%. These results suggest that CDL has a promising potential in reversing drug resistance of breast cancer.