Imaging and cell targeting characteristics of magnetic nanoparticles modified by a functionalizable zwitterionic polymer with adhesive 3,4-dihydroxyphenyl-l-alanine linkages

Multifunctional magnetic nanoparticles (MNPs) modified by a zwitterionic polymer (pCBMA–DOPA2) containing one poly(carboxybetaine methacrylate) (pCBMA) chain and two 3,4-dihydroxyphenyl-l-alanine (DOPA) residue groups were developed. Results showed that MNPs modified by pCBMA were not only stable in complex media, but also provided abundant functional groups for ligand immobilization. The pCBMA–DOPA2 MNPs had a hydrodynamic particle size of about 130 nm, a strong saturation magnetization of 110.2 emu/g Fe and a high transverse relaxivity of 428 mm−1 s−1. Long-term stability in phosphate-buffered saline (PBS) and 10% NaCl solution was achieved for over six months. Compared to MNPs coated with dextran, pCBMA–DOPA2 MNPs presented better stability in 100% human blood serum at 37 °C. Macrophage cell uptake studies revealed that the uptake ratio of pCBMA–DOPA2 MNPs was much lower than that of dextran MNPs. Furthermore, quantitative analysis results showed that after pCBMA–DOPA2 MNPs were conjugated with a targeting RGD peptide, uptake by human umbilical vein endothelial cell (HUVEC) was notably increased, which was further visualized by magnetic resonance imaging (MRI).