The potential of pH-responsive PEG-hyperbranched polyacylhydrazone micelles for cancer therapy

pH-responsive hyperbranched polymers have attracted much attention due to their unique properties for tumor-targeted drug delivery. In this study, we describe a pH-responsive drug carrier, poly (ethylene glycol) (PEG)-hyperbranched polyacylhydrazone (HPAH), which can form nanoscale micelles to be used as anti cancer drug carriers with pH-controlled drug release. The molecular structure of PEG-HPAH was confirmed by nuclear magnetic resonance spectroscopy (NMR) and Fourier transform infrared spectroscopy (FTIR). The drug-loaded micelles with a diameter of approximately 190 nm, were prepared using a dialysis method against PBS with a pH of 8.0. The drug-loaded micelles showed the desired pH-dependent drug release properties. The drug release levels were low at neutral and alkaline pH, but increased significantly with a decrease in the pH of the medium. Intracellular uptake results indicated that the PEG-HPAH-drug micelles could efficiently deliver chemotherapeutic drugs into the cells. In addition, it was found that the subcellular localization of the drug-loaded micelles was different from that of free drugs, in which the drug-loaded micelles were mainly in the cytoplasm. The docetaxel (DTX)-loaded PEG-HPAH micelles presented a high cytotoxic activity against tumor cells in vitro. When combined with the administration of glucose, the PEG-HPAH-DTX micelles exhibited a superior anti-tumor efficacy and a lower systemic toxicity in vivo. The biodistribution profile showed increased accumulated drug levels in tumor tissue and plasma in micelles treated group. The results indicate that the nanoscale PEG-HPAH-DTX micelles may serve as a selective tumor-targeting drug delivery system.