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Scientists: only large nanoparticles from bacteria can be used in medicine
Krasnoyarsk scientists examined the properties of ferrihydrite mineral nanoparticles obtained with the help of bacteria. The researchers found that particles larger than two nanometers are suitable for biomedical applications. Only they form a sufficiently dense core, which determines the magnetic properties necessary for medicine. The results of the study are published in the Journal of Alloys and Compounds (Knyazev et al., Magnetic anisotropy and core-shell structure origin of the biogenic ferrihydrite nanoparticles).
Ferrihydrite is an important mineral that participates in the vital activity of living organisms, including humans. For example, the protein apoferritin in our liver is a particle of ferrihydrite, "packed" in a shell of organic compounds. For the synthesis of natural ferrihydrite, some types of bacteria can be used. The biocompatibility of the material makes it promising for medicine. However, for successful application, it is important to study the properties of nanoparticles in detail.
Physicists of the Krasnoyarsk Scientific Center SB RAS together with colleagues from the Siberian Federal University have discovered the dependence of the magnetic properties of ferrihydrite on the size of nanoparticles and the density of their nucleus. Ferrihydrite has a core–shell structure, while in particles larger than two nanometers, a core is formed that is denser in structure than the shell.
Scientists isolated ferrihydrite particles several nanometers in size from the biomass of Klebsiella oxytoca bacteria. As in the human body, such nanoparticles consist of a dense core in a protein shell. It is noteworthy that it minimizes magnetic interactions between particles. This allowed physicists to focus on studying the magnetism of iron atoms in the nuclei of individual nanoparticles.
Nanoparticles ranging in size from one and a half to three and a half nanometers were used in the study. Scientists have discovered that the magnetic properties depend on the particle size. In the course of subsequent experiments, it turned out that the culprit of the difference is the nuclei of particles, or rather their presence. It turned out that a solid core is formed only in nanoparticles larger than two nanometers, whereas small ones consist of a low-density material and have no core at all.
"The conditions of ferrihydrite formation significantly affect the physical properties of its nanoparticles, in particular, its crystallinity and interactions between individual particles. The magnetic properties, and consequently the application, strongly depend on the structure of the particle. The dense core provides nanoparticles with the best magnetic properties and makes it more suitable for use in medicine, for example, for drug delivery or point thermal effects on foci of diseases in the body," Yuri Vladimirovich Knyazev, a researcher at the L. V. Kirensky Institute of Physics of the Russian Academy of Sciences, Candidate of Physical and Mathematical Sciences, commented on the results of the study.
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