Uptake and persistence of bacterial magnetite magnetosomes in a mammalian cell line: Implications for medical and biotechnological applications.

Jefferson Cypriano,Fernando P Almeida,Fernanda Abreu,Gabriele Vargas,Jacques Werckmann,Dennis A Bazylinski,Marcos Farina,Adriana Lopes Dos Santos,Karen T Silva,Pedro Leão,Ulysses Lins,Yogendra Kumar Mishra

doi:10.1371/journal.pone.0215657

Abstract

Magnetotactic bacteria biomineralize intracellular magnetic nanocrystals surrounded by a lipid bilayer called magnetosomes. Due to their unique characteristics, magnetite magnetosomes are promising tools in Biomedicine. However, the uptake, persistence, and accumulation of magnetosomes within mammalian cells have not been well studied. Here, the endocytic pathway of magnetite magnetosomes and their effects on human cervix epithelial (HeLa) cells were studied by electron microscopy and high spatial resolution nano-analysis techniques. Transmission electron microscopy of HeLa cells after incubation with purified magnetosomes showed the presence of magnetic nanoparticles inside or outside endosomes within the cell, which suggests different modes of internalization, and that these structures persisted beyond 120 h after internalization. High-resolution transmission electron microscopy and electron energy loss spectra of internalized magnetosome crystals showed no structural or chemical changes in these structures. Although crystal morphology was preserved, iron oxide crystalline particles of approximately 5 nm near internalized magnetosomes suggests that minor degradation of the original mineral structures might occur. Cytotoxicity and microscopy analysis showed that magnetosomes did not result in any apparent effect on HeLa cells viability or morphology. Based on our results, magnetosomes have significant biocompatibility with mammalian cells and thus have great potential in medical, biotechnological applications.

Highlights

Nano-sized magnetic particles that functionally integrate into cells and subcellular structures are versatile tools for monitoring cell position and function in vivo, as well as for the development of drug-delivery systems [1]
human cervix epithelial (HeLa) cells were grown in Dulbecco Modified Eagle Medium (DMEM) with 10% fetal bovine serum (FBS) at 37 ̊C in 5% CO2, as recommended by the American Type Culture Collection
transmission electron microscopy (TEM) observation of purified magnetite magnetosomes from M. blakemorei strain MV-1 showed the presence of the magnetosome membrane surrounding each crystal (Fig 1A) confirming the homogeneity and potential reproducibility of the sample

Summary

Introduction

Nano-sized magnetic particles that functionally integrate into cells and subcellular structures are versatile tools for monitoring cell position and function in vivo, as well as for the development of drug-delivery systems [1]. Several applications using bacterial magnetosomes have been proposed and are currently under investigation for medical diagnosis including magnetic resonance imaging contrast, drug delivery, magnetic fluid hyperthermia therapy, and DNA extraction techniques [3,4,5,6,7]. Many of these applications are well described and documented, showing the advantages of using bacterial magnetosomes over synthetic magnetic nanocrystals [8]. Because of the presence of the membrane containing proteins in the structure of magnetosomes, they are more functionalized by bioconjugation techniques [8]

Methods

Results

Conclusion