Gold-coated magnetic nanoparticle as a nanotheranostic agent for magnetic resonance imaging and photothermal therapy of cancer

Because of their great scientific and technological potentials, iron oxide nanoparticles (IONPs) have been the focus of extensive investigations in biomedicine over the past decade. Additionally, the surface plasmon resonance effect of gold nanoparticles (AuNPs) makes them a good candidate for photothermal therapy applications. The unique properties of both IONPs (magnetic) and AuNPs (surface plasmon resonance) may lead to the development of a multi-modal nanoplatform to be used as a magnetic resonance imaging (MRI) contrast agent and as a nanoheater for photothermal therapy. Herein, core-shell gold-coated IONPs (Au@IONPs) were synthesized and investigated as an MRI contrast agent and as a light-responsive agent for cancer photothermal therapy. The synthesized Au@IONPs were characterized by UV-visible spectroscopy, transmission electron microscopy (TEM), dynamic light scattering (DLS), and zeta potential analysis. The transverse relaxivity (r (2)) of the Au@IONPs was measured using a 3-T clinical MRI scanner. Through a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, the cytotoxicity of the Au@IONs was examined on a KB cell line, derived from the epidermal carcinoma of a human mouth. Moreover, the photothermal effects of Au@IONPs in the presence of a laser beam (lambda = 808 nm; 6.3 W/cm(2); 5 min) were studied. The results show that the Au@IONPs are spherical with a hydrodynamic size of 33 nm. A transverse relaxivity of 95 mM(-1) S-1 was measured for the synthesized Au@IONPs. It is evident from the MTT results that no significant cytotoxicity in KB cells occurs with Au@IONPs. Additionally, no significant cell damage induced by the laser is observed. Following the photothermal treatment using Au@IONPs, approximately 70% cell death is achieved. It is found that cell lethality depended strongly on incubation period and the Au@IONP concentration. The data highlight the potential of Au@IONPs as a dual-function MRI contrast agent and photosensitizer for cancer photothermal therapy.