Multifunctional Mixed Micelles for Efficient Docetaxol Delivery for Cancer Therapy

The objective of this study was to build mixed micelles based on two functional co-polymers, including the redox-sensitive polymer-drug conjugate methoxy poly(ethylene glycol)-poly(γ-benzyl l-glutamate)-disulfide-docetaxel (PEG-PBLG-SS-DTX) and the actively targeting methoxy poly(ethylene glycol)-folic acid (PEG-FA), for enhanced target specificity and improved anticancer efficiency of docetaxel (DTX). The spherical PEG-PBLG-SS-DTX/PEG-FA mixed micelles prepared by the dialysis method revealed a narrowly distributed size at 129.7±2.1 nm with low polydispersity of 0.10±0.02. Furthermore, the critical micelle concentration of the mixed micelles was 5.08 μg mL^-1 , indicating excellent self-assembly ability in water and stability against dilution in blood circulation. The in vitro release study revealed that the conjugated DTX was rapidly released in response to dl-dithiothreitol (DTT), a reducing agent. Only 12.3 % of DTX was released from the mixed micelles after 120 h in the absence of DTT. However, the accumulative release of DTX dramatically accelerated and reached more than 40 % in 120 h after addition of DTT. The in vitro cytotoxicity, cellular uptake and cell apoptosis experiments on the mixed micelles were performed using MTT assay, fluorescence inverted microscopy and flow cytometric analysis, and 4',6-diamidino-2-phenylindole (DAPI) staining, respectively, on folate receptor (FR)-negative A549 and FR-positive MCF-7 cells. The mixed micelles could be taken up efficiently by MCF-7 cells by FR-mediated endocytosis compared with PEG-PBLG-SS-DTX micelles. Furthermore, remarkable cytotoxicity and cell apoptosis were identified for the mixed micelles against MCF-7 cells, which was consistent with the results of the cellular uptake study. On the basis of these results, the redox-sensitive PEG-PBLG-SS-DTX/PEG-FA mixed micelles using FA as a targeting ligand revealed prominent antitumor efficiency and might be a latent drug carrier for cancer chemotherapy.