Green synthesis of biocompatible superparamagnetic iron oxide-gold composite nanoparticles for magnetic resonance imaging, hyperthermia and photothermal therapeutic applications

Magnetic nanocomposites are extensively used for biomedical applications such as drug delivery, diagnosis, and therapeutics, etc. Here we report a green synthesis of biocompatible, superparamagnetic, and near-infrared absorbing, iron oxide-gold composite nanoparticles (IO–Au NPs) using aqueous leaf extract of a medicinal plant Pimenta dioica for biomedical applications. The MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay was performed to assess the cytotoxicity of the IO-Au NPs in-vitro. Results of the MTT assay show that the green synthesized IO-Au NPs are safe for cells up to a high concentration of 500 μg/ml. The IO-AuNPs exhibit a superparamagnetic behavior with a large magnetization of 65 emu/g. These IO-Au NPs exhibit a high relaxivities ratio (r2/r1) of 13.20 (r1 = 10.67 s−1 mM−1 and r2 = 140.87 s−1 mM−1 respectively), indicating the potential of these IO-Au NPs as a T2 contrast agent. Magnetic resonance imaging of chicken tissue and poultry heart has been done to confirm the contrast enhancement performance of these nanoparticles. Moreover, the magnetic heating efficacy of the green synthesized IO-Au NPs has been evaluated in an external magnetic field. Owing to their excellent optical property, these green synthesized IO-Au NPs have great potential for NIR photothermal applications. The results of this study suggest that these IO-Au NPs could be used as theranostic agents for in-vivo biomedical imaging and therapeutics.