In vitro killing effect of doxorubicin and Bcl-2 siRNA co-delivered by polymeric nanomicelles on MCF-7 human breast cancer cells

Objective: To prepare polymeric nanomicelles capable of simultaneously loading doxorubicin (DOX) and Bcl-2 small interfering RNA (Bcl-2 siRNA), and to explore their in vitro cytotoxicity and cellular uptake in MCF-7 human breast cancer cells. Methods: Copolymer poly(ethylene glycol)-g-polyethylenimine-g-poly(γ-benzyl-L-glutamate) was synthesized by the combination of reductive amination and carbodiimide methods, and its chemical structure was verified by ¹H NMR. Empty and drug-loaded copolymeric nanomicelles were prepared by dialysis method and characterized by transmission electron microscope and dynamic light scattering. The ability of the nanomicelles to compress Bcl-2 siRNA was measured by by agarose gel electrophoresis method. The release profiles of DOX and Bcl-2 siRNA from the nanomicelles were explored by means of fluorescence spectrometry and dialysis method. The in vitro cytotoxicity and cellular uptake of DOX and Bcl-2 siRNA co-loaded nanomicelles in MCF-7 human breast cancer cells were characterized by MTT assay and confocal laser scanning microscopy, respectively. Results: The critical micelle concentration of the copolymer was about 4 mg/L, and the sizes of self-assembled empty and drug-loaded nanomicelles were smaller than 200 nm. The drug-loading efficiency and drug-loading content of DOX in the nanomicelles were 88.7% and 15.1%, respectively. The DOX-loaded nanomicelles could efficiently compress Bcl-2 siRNA when an N/P ratio was ≥64. The zeta potential of DOX and Bcl-2 siRNA co-loaded nanomicelles was +30 mV. The release behavior of the cargoes from the nanomicells was pH-sensitive, and the release of Bcl-2 siRNA was more sensitive to acidic pH than that of DOX. The nanomicelles could simultaneously deliver DOX and Bcl-2 siRNA into MCF-7 cells, and the co-delivered DOX and Bcl-2 siRNA significantly increased the cytotoxicity of DOX (P<0.05). Conclusion: The polymeric nanomicelles can co-load DOX and Bcl-2 siRNA and deliver them into MCF-7 cells, and DOX in combination with Bcl-2 siRNA can synergistically inhibit the growth of MCF-7 cells and promote cell apoptosis, suggesting that the nanomicells may be a promising carrier for the co-delivery for chemotherapeutics and genes.