Cisplatin Loaded Poly(L-glutamic acid)-g-Methoxy Poly(ethylene glycol) Complex Nanoparticles for Potential Cancer Therapy: Preparation, In Vitro and In Vivo Evaluation

A series of novel polypeptide-based graft copolymer poly(L-glutamic acid)-graft-methoxy poly(ethylene glycol) (PLG-g-mPEG) was synthesized through a Steglich esterification reaction of PLG with mPEG. The structure of the copolymers was confirmed by nuclear magnetic resonance spectra (NMR) and gel permeation chromatography (GPC). MTT assay demonstrated that the PLG-g-mPEGs had good cell compatibility. The unreacted carboxyl groups of the PLG-g-mPEGs were used to complex cisplatin to form polymer-metal complex nanoparticles (CDDP/PLG-g-mPEG) for cancer therapy. The average hydrodynamic radius of the CDDP/PLG-g-mPEG nanoparticles was in the range of 14–25 nm, which was beneficial for solid tumor targeting delivery. A sustained release without initial burst was achieved for the CDDP/PLG-g-mPEG nanoparticles, indicating that the CDDP-loaded nanoparticles had great potential to suppress the drug release in blood circulation before the nanoparticles had arrived at targeting tumors. The CDDP/PLG-g-mPEG nanoparticles showed a much longer blood retention profile as compared with the free CDDP. This indicated that the CDDP-loaded nanoparticles had much more opportunity to accumulate in tumor tissue by exerting the EPR effect. In vitro tests demonstrated that the CDDP/PLG-g-mPEG nanoparticles could inhibit the proliferation of HeLa, MCF-7 and A549 cancer cells. At equal dose (4 mg kg–1), the CDDP/PLG-g-mPEG nanoparticles showed comparable in vivo antitumor efficacy and significantly lower systemic toxicity as compared with free cis-Diaminedichloroplatinum (cisplatin, CDDP) in MCF-7 tumor bearing mice. These suggested that the CDDP/PLG-g-mPEG nanoparticle drug delivery system had a great potential to be used for cancer therapy.