Superparamagnetic hyperthermia and cytotoxicity properties of bimagnetic core-shell nanoparticles synthesized by solvothermal reflux method

Magnetic properties of spinel ferrites nanoparticles (NPs) were well studied for various applications, including biomedical applications such as magnetic hyperthermia agents, magnetic resonance imaging (MRI) contrast agents, targeted drug delivery agents, etc., Magnetic properties of these nanoparticles were altered by metal cations substitution as well as variation of size and shape of nanoparticles. Here hard-soft magnetic materials based magnetic exchange coupled bimagnetic CoFe2O4-CaFe2O4, and CaFe2O4-CoFe2O4 core-shell nanopar-ticles (CSNPs) with narrow size distribution were synthesized to alter their magnetic properties. Structural, morphology, magnetic, superparamagnetic hyperthermia (SPHT), and cytotoxicity properties of these NPs were reported. Unimagnetic phase CoFe2O4, CaFe2O4 nanoparticles were also studied for comparison. Though CaFe2O4 macrocrystals crystallizes in orthorhombic structure, CaFe2O4 nanocrystals crystallizes in cubic spinel structure whereas both macro-and nanoparticles of CoFe2O4 crystallizes in spinel structure. Scanning electron nanographs (electrongraphs) of all samples show narrow size distributed spherical particles of average particle size of around 10 nm and is confirmed by transmission electron nanographs. Room temperature magnetic hysteresis loop of all samples were shown superparamagnetic nature with very low coercive field. Bimagnetic CSNPs show higher specific heat generation rate (SHR) or specific magnetic field energy absorption rate (SAR) of superparamagnetic nanoparticles (474 W/g for CaFe2O4-CoFe2O4 CSNPs under H = 35.5 kAm-1 and f = 316 kHz field parameters ) compared to counterpart unimagnetic nanoparticles (407 W/g for CaFe2O4 NPs). However, the SAR decreases with increase of magnetic nanoparticles (MNPs) concentration in the dispersion medium due to reduced superparamagnetic relaxation time resulting from magnetic dipole interactions among dispersed nanoparticles. This is also confirmed in SPHT properties of dispersant removed CSNPs. Cytotoxicity studies show that cell viability increases with MNPs concentration due to increased colorimetric interference of iron oxide and inhomogeneous distribution of MNPs, due to magnetic interactions, among cell culture wells, at higher concentration. These CSNPs may be used for localized SPHT in cancer therapy.