Screening of novel RGD peptides to modify nanoparticles for targeted cancer therapy.

New targeted RGD peptides obtained by solid phase peptide synthesis (SPPS) were successfully screened by Molecular Operating Environment (MOE) and used for the building of the 6-O-carboxymethyl chitosan based carrier with an active target on the surface. CRGDYC-6-O-carboxymethyl chitosan based nanoparticles (NPs) loaded with doxorubicin hydrochloride (DOX) were successfully prepared by an ionic gelation method with the carrier synthesized before. Synthesis conditions and formulation parameters were optimized by determining the characteristics of nanoparticles including the particle size and drug encapsulation efficiency. 6-O-Carboxymethyl chitosan concentration, calcium chloride concentration and calcium chloride/6-O-carboxymethyl chitosan ratio all had effects on the particle size and drug encapsulation efficiency. Nanoparticles with an average diameter of 193.4 nm, an average drug loading efficiency of up to 69.5% and an average drug loading of up to 0.395% were prepared successfully with the optimal formulation. Flow cytometry and confocal microscopy analyses showed that the cellular uptake of DOX in human breast cancer cell lines (MCF-7) was higher in the CRGDYC-modified nanoparticles compared with the unmodified nanoparticles. In vivo imaging showed that the distribution of CRGDYC-modified nanoparticles in the tumor site was higher compared with the unmodified nanoparticles. These results suggest that CRGDYC-6-O-carboxymethyl chitosan may be a promising cancer targeting carrier which can enhance the intracellular uptake and cytotoxicity of the drug-loaded nanoparticles.