Multifunctional PEG-carboxylate copolymer coated superparamagnetic iron oxide nanoparticles for biomedical application

Biocompatible magnetite nanoparticles (MNPs) were prepared by post-coating the magnetic nanocores with a synthetic polymer designed specifically to shield the particles from non-specific interaction with cells. Poly(ethylene glycol) methyl ether methacrylate (PEGMA) macromonomers and acrylic acid (AA) small molecular monomers were chemically coupled by quasi-living atom transfer radical polymerization (ATRP) to a comb-like copolymer, P(PEGMA-co-AA) designated here as P(PEGMA-AA). The polymer contains pendant carboxylate moieties near the backbone and PEG side chains. It is able to bind spontaneously to MNPs; stabilize the particles electrostatically via the carboxylate moieties and sterically via the PEG moieties; provide high protein repellency via the structured PEG layer; and anchor bioactive proteins via peptide bond formation with the free carboxylate groups. The presence of the P(PEGMA-AA) coating was verified in XPS experiments. The electrosteric (i.e., combined electrostatic and steric) stabilization is efficient down to pH 4 (at 10 mM ionic strength). Static magnetization and AC susceptibility measurements showed that the P(PEGMA-AA)@MNPs are superparamagnetic with a saturation magnetization value of 55 emu/g and that both single core nanoparticles and multicore structures are present in the samples. The multicore components make our product well suited for magnetic hyperthermia applications (SAR values up to 17.44 W/g). In vitro biocompatibility, cell internalization, and magnetic hyperthermia studies demonstrate the excellent theranostic potential of our product. © 2017 Elsevier B.V

Colloidal stability of carboxylated iron oxide nanomagnets for biomedical use

Magnetite nanoparticles (MNP) were synthesized and stabilized with carboxylated compounds citric acid - CA, poly(acrylic acid) - PAA, poly(acrylic acid-co-maleic acid) - PAM, humic acid - HA and gallic acid - GA (polymerizing in situ on the surface). Adsorption isotherms and bonding feature were determined and used to explain the changes in charge and aggregation states and salt tolerance of the MNPs. The thicker layer of macromolecular acids PAA, PAM and HA provides better stability at physiological pH and salt concentration compared to the CA and GA coatings. In addition, Fe(III)-CA complexation promotes the dissolution of the nanoparticles. The biocompatibility of the polyacid-coated MNPs was tested in cell proliferation experiments