Heating Efficiency of Different Magnetotactic Bacterial Species: Influence of Magnetosome Morphology and Chain Arrangement

Magnetotactic bacteria have been proposed as ideal biological nanorobots due to the presence of an intracellular chain of magnetic nanoparticles (MNPs), which allows them to be guided and controlled by external magnetic fields and provides them with theragnostic capabilities intrinsic to magnetic nanoparticles, such as magnetic hyperthermia for cancer treatment. Here, we study three different bacterial species, <i>Magnetospirillum gryphiswaldense</i> (MSR-1), <i>Magnetospirillum magneticum</i> (AMB-1), and <i>Magnetovibrio blakemorei</i> (MV-1), which synthesize magnetite nanoparticles with different morphologies and chain arrangements. We analyzed the impact of these parameters on the effective magnetic anisotropy, <i>K</i>_eff, and the heating capacity or Specific Absorption Rate, SAR, under alternating magnetic fields. SAR values have been obtained from the area of experimental AC hysteresis loops, while <i>K</i>_eff has been determined from simulations of AC hysteresis loops using a dynamic Stoner-Wohlfarth model. The results demonstrate a clear relationship between the effective magnetic anisotropy and the heating efficiency of bacteria. As the <i>K</i>_eff value increases, the saturated SAR values are higher; however, the threshold magnetic field required to observe a SAR response simultaneously increases. This factor is crucial to choose a bacterial species as the optimal hyperthermia agent.