ZnO coated CoFe2O4 nanoparticles for multimodal bio-imaging

Abstract

The potential of CoFe₂O₄–ZnO core–shell nanoparticles for fluorescence optical imaging and as a contrast agent for magnetic resonance imaging (MRI) is demonstrated. Two different core–shell CoFe₂O₄–ZnO nanoparticle geometries were produced by the wet chemical synthesis method. In one case, the core–shell geometry was made up of individual nanoparticles containing CoFe₂O₄ as the core and ZnO as the shell whereas in the other case, agglomerates of CoFe₂O₄ nanoparticles were encapsulated within ZnO capsules. It was observed that the CoFe₂O₄–ZnO core–shell nanoparticles with a unique geometry in which CoFe₂O₄ ferrite nanoparticles agglomerates were present within ZnO capsules yielded a very high value of transverse proton relaxivity (264.6 mM⁻¹ s⁻¹) when compared to the transverse proton relaxivity exhibited by the individual core–shell nanoparticles (31.8 mM⁻¹ s⁻¹). Using HeLa cells to which the core–shell nanoparticles were attached, it is shown that the CoFe₂O₄–ZnO nanoparticles can also be used as contrast agents in fluorescence imaging. The as-synthesized CoFe₂O₄–ZnO core–shell nanoparticles were also found to exhibit biocompatibility towards the MCF-7 cell line. Taken together, this opens up new avenues for superparamagnetic ferrite based nanoparticles in bio-imaging applications.