Development of citrate-stabilized Fe3O4 nanoparticles: Conjugation and release of doxorubicin for therapeutic applications

We demonstrate a single-step facile approach for the fabrication of citric acid functionalized (citrate-stabilized) Fe₃O₄ aqueous colloidal magnetic nanoparticles (CA-MNP) of size 8-10 nm using soft chemical route. The surface functionalization of Fe₃O₄ nanoparticles with citric acid was evident from infrared spectroscopy, thermal and elemental analyses, and zeta-potential measurements. The drug-loading efficiency of CA-MNP was investigated using doxorubicin hydrochloride (DOX) as a model drug to evaluate their potential as a carrier system. The quenching of fluorescence intensity and decrease in surface charge of drug loaded CA-MNP strongly suggest the interaction/attachment of drug molecules with CA-MNP. More specifically, the present investigation discusses a method for entrapping positively charged drugs onto the surface of negatively charged CA-MNP through electrostatic interactions and suggests that bound drug molecules will be released in appreciable amounts in the mild acidic environments of the tumors. Furthermore, the aqueous colloidal stability, optimal magnetization, good specific absorption rate (under external AC magnetic field) and cytocompatibility with cells suggested that CA-MNP is appropriate candidate for biomedical applications.