Novel pH-sensitive chitosan-derived micelles loaded with paclitaxel

A series of pH-sensitive graft copolymers, N-octyl-N-(2-carboxyl-cyclohexamethenyl) chitosan derivatives were synthesized and characterized by FTIR, 1H NMR and elemental analysis, and their physical properties were measured with differential scanning calorimetry and X-ray diffraction spectrometry. The critical micelle concentrations (CMCs) of the modified chitosan determined by using pyrene as a hydrophobic probe in fluorescence spectroscopy were from 11 to 72 μg/ml. The graft polymers can form micelles solubilizing paclitaxel, with drug-loading rate ranging from 30.47% to 48.10% and entrapment efficiency from 42.22% to 59.24%. Cytotoxicities of carrier against tumor cells estimated that carriers were nearly non-cytotoxic. Additionally, the results of pH-sensitivity and drug release experiments showed that the micelles were highly sensitive to mild acidic conditions (pH 5.5) while reasonably stable at physiological conditions (pH 7.4). Therefore, chitosan-derived micelle may be a potential anti-tumor drug delivery system for chemotherapy of cancer.