Fe3O4 magnetic nanoparticles coated by citric acid were synthesized via co-precipitation

and NH2-PEG-NH2-modified magnetic nanoparticles (PCMNPs) were thus prepared by carbodiimide chemistry to improve biological application of the nanoparticles. The surface morphology

chemical structures

crystal structures

thermostability and magnetic properties of the nanoparticles were characterized with scanning electron microscopy (SEM)

Lorenz transmission electron microscopy (TEM)

Malvern laser particle size analyzer

X-ray analysis (XRD)

Fourier transform infrared spectroscopy (FTIR)

thermogravimetric analysis (TGA) and vibrating sample magnetometer (VSM). Doxorubicin (DOX) was used as a model drug to study the PCMNPs drug loading and release behaviors

and DOX-loaded nanoparticles (PCMNPs-DOX) were then prepared

accordingly. The PEG modifier nanoparticles were roughly spherical with a relatively uniform size of about 15 nm. The size analysis showed that the as-synthesized magnetic nanoparticles were of statistical distribution with a maximal diameter of 33 nm. FTIR data and TG results all revealed that polymer PEG formed complexes on Fe3O4 surface. VSM result disclosed that no coercivity or remanence could be observed for samples

suggesting the superparamagnetic properties of the particles. The saturation magnetization (Ms) of the MNPs was about 68 A·m2/kg

which could be used for magnetic drug targeting delivery

hyperthermia treatment and magnetic resonance imaging. Consequently

the drug loading capacity in water was about 83%. The overall release efficiency was higher at a lower pH (5.0) than at physiological pH (7.4)

which was important for the killing of relatively acidic tumor cells. Furthermore

the release of DOX from PCMNPs in both conditions showed that drug molecules released at a sustained pattern and complete release of drug was not attained. All the characterizations indicated that the PEG modifier nanoparticles showed superparamagnetic performance

high drug loading ability and sustained release behavior. Therefore

the as-synthesized magnetic nanoparticles could exhibit good drug loading and sustained-release effect

which provided a prospective method for cancer chemotherapy.