Intracellular transformation and disposal mechanisms of magnetosomes in macrophages and cancer cells

Abstract

Magnetosomes are magnetite nanoparticles biosynthesized by magnetotactic bacteria. They have been proposed for several biomedical applications mostly focused on the treatment and diagnosis of cancer. In this work we follow the intracellular long-term fate of magnetosomes in cancer cells and macrophages. We observe that cells dispose of magnetosomes using three main mechanisms: splitting into daughter cells in cell division, excretion to the surrounding environment and intracellular degradation. A deeper insight into the later mechanism by means of X-ray absorption spectroscopy reveals that in both cell types studied there is a first oxidation of magnetite to maghemite and a subsequent appearance of ferrihydrite, the iron mineral phase stored in the cores of ferritin proteins, suggesting that cells use the iron released from the degradation of magnetosomes to load ferritin.