[pH-sensitive micelles loaded paclitaxel using carboxymethyl chitosan-palmitic acid mediated by cRGD]

cRGD-carboxymethyl chitosan-palmitic acid (cRGD-CMCh-PA) was synthesized and a pH- sensitive paclitaxel-loaded cRGD-CMCh-PA micelles（PTX-cRGD-CMCh-PA） was prepared with the film dispersion method; related substances were characterized by FT-IR and (1)H NMR. PTX-cRGD-CMCh-PA micelles were studied with the particle size distribution, zeta potential, morphology and release behavior in vitro was investigated by the method of equilibrium dialysis. In vitro cytotoxicity of different formulations on A549 cells was tested by MTT assay. The uptake process of micelles was explored using confocal microscopy and a live cell station was used to observe the dynamic phagocytosis. The subcutaneous and orthotropic tumor models were built to study the distribution of Di R-labeled micelles by near-infrared fluorescence（NIR） imaging system. The FT-IR spectra and (1)H NMR spectra confirmed the successful conjugation of cRGD-CMCh-PA polymer and the degree of carboxymethyl and the palmitic acid grafted on chitosan were 45.0% and 15.0%. PTX-cRGD-CMCh-PA micelles were prepared with particle size of（162.9 ± 1.5） nm, zeta potential of +26.3 m V and encapsulation efficiency and the drug loading of 99.67% and 28.5%, respectively. The micelles released slowly in pH 7.4 whose release curves were accorded with the Higuchi equation; they had an initial burst effect in second hours and showed a pH sensitive release behavior in pH 5.3. The IC(50) of PXT-CMCh-PA and PTX-cRGD-CMCh-PA were 2.077 μg·mL(-1) and 0.876 μg·mL(-1), respectively. The cells uptake process of micelles in A549 cells revealed that the micelles were mainly co-located with lysosome and PTX-cRGD-CMCh- PA showed much better targeting effect. The NIR fluorescence imaging results showed that the micelles had a good targeting effect on both subcutaneous and orthotropic tumors. In this study, a novel copolymer cRGD- CMCh-PA was synthesized with a sustained and pH-dependent drug release activity which would potentially become a new carrier for hydrophobic drugs.