Scientists biosynthesise magnetic nanoparticles using bacteria

Researchers at the University of Bayreuth, Germany, have biosynthesised magnetic nanoparticles using bacteria, a process that will become essential to biomedicine and biotechnology.

The team has optimised a process for the isolation and purification of these magnetic nanoparticles from bacterial cells. In initial tests, magnetosomes showed good biocompatibility when incubated with human cell lines. The results, published in the journal Acta Biomaterialia, are a promising step towards the biomedical use of magnetosomes in diagnostic imaging techniques or as a carrier in magnetic drug delivery applications.

The magnetotactic bacterium Magnetospirillum gryphiswaldense produces intracellular magnetic nanoparticles, called magnetosomes. These are arranged in a chain-like manner and form a kind of magnetic compass needle that allows the bacteria to navigate along the Earth’s magnetic field. In contrast to chemically produced nanoparticles, magnetosomes exhibit a uniform shape and size of about 40 nanometres, a perfect crystal structure, and promising magnetic properties.

The criteria for purified magnetosomes

An interdisciplinary team of scientists at the University of Bayreuth has now defined quality criteria for purified magnetosomes, which are required for future applications. These include the uniformity (homogeneity) of magnetosomes, a high degree of purity, and the integrity of the membrane that surrounds each individual magnetosome and provides stability. The Bayreuth researchers established and optimised a method by which magnetosomes can be gently isolated from the bacteria. The newly developed procedure not only fulfils the quality criteria but is also adaptable for the isolation of larger quantities required in the broad range of applications envisioned in biomedicine and biotechnology.

The magnetosome purification process developed in Bayreuth is based on the physical properties of the magnetic nanoparticles. The magnetosomes are separated from other non-magnetic cell components by magnetic columns. Due to the high density of the nanoparticles, an additional ultracentrifugation step allows the removal of residual impurities.

The team tested the quality of the purified magnetosome suspensions using physico-chemical techniques and analysed the biocompatibility in close collaboration with the Jena University Hospital. The team revealed high vitality values of magnetosome-treated human cell lines even at high particle concentrations, indicating good biocompatibility.

The biocompatibility of magnetosomes represent a prerequisite for their use in magnetic imaging techniques and magnetically controlling drug delivery for cancer cells. Moreover, the nanoparticles might have great potential in the field of theranostics, which combines precise diagnosis with subsequent targeted therapy.



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