Heating Efficiency\nof Different Magnetotactic Bacterial\nSpecies: Influence of Magnetosome Morphology and Chain Arrangement

Magnetotactic bacteria have been proposed as ideal biological\nnanorobots\ndue to the presence of an intracellular chain of magnetic nanoparticles\n(MNPs), which allows them to be guided and controlled by external\nmagnetic fields and provides them with theragnostic capabilities intrinsic\nto magnetic nanoparticles, such as magnetic hyperthermia for cancer\ntreatment. Here, we study three different bacterial species, Magnetospirillum gryphiswaldense (MSR-1), Magnetospirillum magneticum (AMB-1), and Magnetovibrio blakemorei (MV-1), which synthesize\nmagnetite nanoparticles with different morphologies and chain arrangements.\nWe analyzed the impact of these parameters on the effective magnetic\nanisotropy, <i>K</i><sub>eff</sub>, and the heating capacity\nor Specific Absorption Rate, SAR, under alternating magnetic fields.\nSAR values have been obtained from the area of experimental AC hysteresis\nloops, while <i>K</i><sub>eff</sub> has been determined\nfrom simulations of AC hysteresis loops using a dynamic Stoner–Wohlfarth\nmodel. The results demonstrate a clear relationship between the effective\nmagnetic anisotropy and the heating efficiency of bacteria. As the <i>K</i><sub>eff</sub> value increases, the saturated SAR values\nare higher; however, the threshold magnetic field required to observe\na SAR response simultaneously increases. This factor is crucial to\nchoose a bacterial species as the optimal hyperthermia agent.