Shell-dependent antimicrobial efficiency of cobalt ferrite nanoparticles

Uniformly shaped and sized superparamagnetic nanoparticles (NPs) have recently received increasing attention due to their prospective applications in theranostics, sensing and as antimicrobials. However, utilization of magnetic NPs in nanomedicine largely depends on their properties, which, in turn, are influenced by the size, structure and composition of the core and the nature of stabilization shell. This paper highlights the significant influence of stabilizing shell of superparamagnetic cobalt ferrite NPs on the antimicrobial efficacy against several kinds of pathogenic microorganisms. Two very popular preparation methods of biocompatible magnetic NPs, namely, co-precipitation from alkaline solutions containing Co(II) and Fe(III) salts and L-lysine (Lys) as well as thermal decomposition of organometallic Co(II) and Fe(III) precursors in the presence of oleic acid were applied. The properties of resulting NPs are characterized and discussed herein. Surprisingly, highly efficient bactericidal behaviour of cobalt ferrite NPs capped with oleine shell compared to that of CoFe2O4@Lys, was ascribed to the differences in their surface charge and more grained structure of the former.