Biotinylated thermoresponsive micelle self-assembled from double-hydrophilic block copolymer for drug delivery and tumor target

A multifunctional micellar drug carrier formed by the thermosensitive and biotinylated double-hydrophilic block copolymer (DHBC), biotin-poly(ethylene glycol)-block-poly(N-isopropylacrylamide-co-N-hydroxymethylacrylamide) (biotin-PEG-b-P(NIPAAm-co-HMAAm)), was designed and prepared. The P(NIPAAm-co-HMAAm) block with an molar feed ratio of NIPAAm and HMAAm (10:1) was identified to exhibit the reversible phase transition at the lower critical solution temperature (LCST) of 36.7 °C. Cytotoxicity study indicated that the biotin-PEG-b-P(NIPAAm-co-HMAAm) copolymer did not exhibit obvious cytotoxicity. The block copolymer was capable of self-assembling into micelle in water. Transmission electron microscopy showed that the self-assembled micelles were regularly spherical in shape. The anticancer drug methotrexate (MTX) was loaded in the micelles and the in vitro release behaviors of MTX at different temperatures were investigated. The association of biotin molecule with the copolymer was confirmed by a unique capillary electrophoresis immunoassay (CEIA) method based on enhanced chemiluminescence (CL) detection. The fluorescence spectroscopy analysis as well as confocal microscopy studies confirmed the DHBC drug carriers could specifically and efficiently bind to cancer cells with pretreatment of biotin-transferrin, suggesting that the multifunctionalized DHBC micelle may be a useful drug carrier for tumor targeting.