The synthesis and characterization of a magnetite nanoparticle with potent antibacterial activity and low mammalian toxicity

Magnetite has shown some promise as a biomedical material and antibacterial agent; however the benefits are normally only realized when it is used in combination with other metals or drugs. Unfunctionalized magnetite may be a biocompatible alternative. This report discusses the synthesis and potent antibacterial activity, with low associated mammalian organ toxicity, of nanomagnetite particles. Magnetite (Fe3O4) nanoparticles were electrochemically prepared in a green surfactant-free, closed water loop system. These materials, characterized by X-ray diffraction, FTIR, and vibrational magnetometry, also appear contaminated with Fe-O-O-H functionalities. This physical characterization is accompanied by a computational investigation of truncated clusters showing that a magnetite-derived cluster of 7 iron atoms is a sufficient model to generate the vibrational frequencies experimentally observed in magnetite using DFT calculations. The nanoparticles, evaluated for antibiotic activity, were shown to have minimum inhibitory concentrations of 2.8 and 2.0 mu g/mL against E. coli and S. aureus respectively. This is both a 100-fold lower concentration than the human cytotoxic dose determined by an MTT assay and is also comparable to the effective dose of traditional antibiotics. A dose-dependent decrease in catalase activity and an increase in the levels of lipid peroxidation suggests that these nanoparticles act through damaging the anti-oxidant systems in cells. However, renal and hepatic damage was only observed at daily doses (2 weeks) of 100 mu g/mL and higher. This significant therapeutic window suggests that these materials might prove useful as potential complementary therapeutics in the future. (C) 2018 Elsevier B.V. All rights reserved.