The effects of poly(zwitterions)s versus poly(ethylene glycol) surface coatings on the biodistribution of protein nanoparticles

Zwitterionic poly(carboxybetaine) (PCB), poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) and non-ionic poly(ethylene glycol) (PEG), which have similar degrees of polymerization, were grafted to branched polyethyleneimine (PEI) to generate PCB-grafted PEI (PEI-PCB), PMPC-grafted PEI (PEI-PMPC) and PEG-grafted PEI (PEI-PEG) copolymers, respectively. These grafted PEI copolymers with almost the same grafting number were coated on the surface of 110 nm bovine serum albumin-poly(N-3-acrylamidophenylboronic acid) (BSA-PAPBA) nanoparticles to make a comparison of the surface decoration effect on the biodistribution of nanoparticles. Compared to the nanoparticles without surface decoration, surface decoration with the copolymers significantly prolonged the circulation time of BSA-PAPBA nanoparticles, leading to remarkable enhancement of tumor uptake of the nanoparticles. The drug accumulation at the tumor site reached more than 10% injected dose per gram of tumor. Among them, the PEI-PMPC-decorated nanoparticles exhibited the best performance in tumor accumulation and anticancer ability. Thus, these surface-decorated nanoparticles may serve as a strong candidate for high tumor accumulation of drug delivery systems.