Bacteria-Synthesized Magnetic Nanoparticles Could Soon Find Biomedical Applications

Researchers have developed a novel process for isolating and purifying magnetic nanoparticles biosynthesized by bacteria.

A new study from the University of Bayreuth in Germany has demonstrated the optimization of a process that encourages bacterial magnetic nanoparticle synthesis. In their initial tests, the magnetosomes - organelles encased in magnetic bacteria - exhibited biocompatibility when incubated with human cell lines. Results of their research appear in the journal Acta Biomaterialia.

Biosynthesizing Magnetosomes

As the researchers explain in the paper, bacterial magnetosomes are "well-defined membrane-enveloped single-domain iron oxide (magnetitte) nanoparticles," noting their susceptibility for genetic and chemical engineering. In their study, researchers used the magnetotactic bacteria strain Magnetospirillum gryphiswaldense, which produces intracellular magnetic nanoparticles.

They then arranged the bacteria in a chain-like manner, forming a rudimentary magnetic needle that allows the string to navigate with respect to the Earth's magnetic field. Unlike artificially synthesized nanoparticles, magnetosomes are remarkably uniform and consistent, measuring an average of 40 nanometers. Additionally, these magnetic particles maintain a crystal structure and promising magnetic properties that could allow them to be used for various biomedical applications. Lastly, magnetosomes are wrapped by an organic membrane that could also host additional biochemical functionalities as needed. These properties make magnetosomes a point of interest for alternative biomedical techniques.

Now, the University of Bayreuth team established a set of criteria to assess the quality of purified magnetosomes, which could guide future real-world applications. These criteria include the homogeneity, or uniformity, of the magnetosomes, a degree of purity, and the integrity of the membrane covering individual magnetosomes.

Researchers also created a method to optimize the isolation of magnetosomes from the bacteria. The proposed method not only meets the quality criteria they set but can also be scaled to larger volumes to be practically feasible for biomedical and biotechnological applications.

Purifying Magnetosomes from M. gryphiswaldense

Their novel method starts by filtering out magnetosomes from other non-magnetic cell components through the use of magnetic columns. Next, based on the nanoparticles' naturally higher density, an additional ultracentrifugation process is employed to remove the remaining impurities. The quality of the resulting magnetosomes is assessed with a variety of physicochemical techniques. For the biocompatibility of synthesized nanoparticles, the University of Bayreuth collaborated with the Jena University Hospital, finding high vitality values on magnetosomes incubated with human cell lines, even at higher concentrations.

According to a University of Bayreuth press release, the biocompatibility test results indicate good results according to "relevant DIN standards," referring to the German Institute of Standardization - which develops and implements standards to ensure quality, environmental protection, safety in industry and science for the public domain.

A 2014 article published in the journal Frontiers in Bioengineering and Biotechnology reviewed a couple of medical applications of magnetosomes, ranging from their use in magnetic resonance imaging (MRI), magnetic hyperthermia, and as a drug delivery medium. It also summarized the toxicity levels and biodistribution of these magnetosomes, citing previous studies focused on each application.