Effect of size and silica coating on structural, magnetic as well as cytotoxicity properties of copper ferrite nanoparticles.

Copper ferrite nanoparticles, synthesized by conventional sol-gel method were calcined at different temperatures. The magnetic, structural, morphological and cytotoxicity analyses of the uncalcined and calcined nanoparticles (NPs) were investigated and compared. Formation of tetragonal structure of CuFe2O4 NPs was observed in XRD patterns. On increasing the temperature, better crystallinity and increased crystallite size were also observed. In the FTIR spectra, bonds corresponding to CH, OH and carboxylate groups gradually disappeared with increasing temperature, while peak corresponding to FeO existed more prominently. NPs calcined at 300 °C (Cu3) exhibited the highest magnetic saturation and lowest retentivity, thereby indicating its superparamagnetic behaviour. Concentration-dependent cytotoxicity values were obtained by invitro MTT (3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide, a tetrazole) assay, Cell Titer assay and Cell Flow Cytometry with Propidium Iodide. NPs calcined at 300 °C, 500 °C and 700 °C exhibited non-toxicity at all the concentrations. Based on magnetic and biocompatibility analyses, Cu3 NPs were found to be the most suitable one to investigate the influence of silica coating on its surface. Presence of silica was confirmed by XRD pattern, FTIR spectrum, SEM and HRTEM micrographs as well as SAED pattern. In M-H curve, superparamagnetic behaviour of the CuFe2O4 core was retained but with reduced magnetic saturation due to magnetically dead layer of silica. An increase in cellular viability was witnessed in case of silica coated CuFe2O4 NPs as compared to uncoated NPs, thus reflecting on its enhanced biocompatibility. Nanosized, superparamagnetic and highly biocompatible characteristics make silica coated CuFe2O4 NPs a potential claimant for biomedical applications.