Spontaneous Formation of Nanoparticles from Peptide–Vinyl Polymer Diblock Hybrids Prepared by RAFT Polymerization and Their Interactions with Cells

Novel polymeric nanoparticles (NPs) with uniform sizes were prepared from peptide-vinyl polymer diblock hybrids by the self-organized precipitation method. Hybrid polymers of polystyrene (PSt) and tetrapeptide (cell-binding epitope RGDS, reverse SDGR, cationic KKKK, and anionic DDDD) were successfully synthesized by combining solid-phase peptide synthesis and reversible addition fragmentation chain transfer polymerization methods. Narrowly dispersed hybrid polymers (polydispersity index < 1.25, M n 14 000-17 000) were obtained. Altering the preparation conditions easily tuned the size and size distribution of the NPs. When the ζ-potentials for the NP suspensions were measured at pH 6.0, the obtained values corresponded to the net charge of each peptide segment. More importantly, the NPs could encapsulate fluorescent Nile red (NR) and magnetic iron oxide NP (MNP), which might be suitable for fluorescent imaging and magnet-induced patterning of cells, respectively. The interactions of NPs with cells (NIH/3T3 fibroblast) and the magnetic effects were examined for NR/MNP-loaded PSt-RGDS and -SDGR NPs. Both NPs were readily incorporated into cells, but only NR/MNP-loaded PSt-RGDS NP showed magnetic responsiveness in cell adhesion and cultures.