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Magnetotactic bacteria are aquatic microorganisms that internally biomineralize chains of magnetic nanoparticles (called magnetosomes) and use them as a compass. Here it is shown that magnetotactic bacteria of the strain Magnetospirillum gryphiswaldense present high potential as magnetic hyperthermia agents for cancer treatment. Their heating efficiency or specific absorption rate is determined using both calorimetric and AC magnetometry methods at different magnetic field amplitudes and frequencies. In addition, the effect of the alignment of the bacteria in the direction of the field during the hyperthermia experiments is also investigated. The experimental results demonstrate that the biological structure of the magnetosome chain of magnetotactic bacteria is perfect to enhance the hyperthermia efficiency. Furthermore, fluorescence and electron microscopy images show that these bacteria can be internalized by human lung carcinoma cells A549, and cytotoxicity studies reveal that they do not affect the viability or growth of the cancer cells. A preliminary in vitro hyperthermia study, working on clinical conditions, reveals that cancer cell proliferation is strongly affected by the hyperthermia treatment, making these bacteria promising candidates for biomedical applications., (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Measurement of specific absorption rate (SAR) of magnetic nanoparticles is crucial to assert their potential for magnetic hyperthermia. To perform this task, calorimetric methods are widely used. However, those methods are not very accurate and are difficult to standardize. In this paper, we present AC magnetometry results performed with a lab-made magnetometer that is able to obtain dynamic hysteresis-loops in the AC magnetic field frequency range from 50 kHz to 1 MHz and intensities up to 24 kA m-1. In this work, SAR values of maghemite nanoparticles dispersed in water are measured by AC magnetometry. The so-obtained values are compared with the SAR measured by calorimetric methods. Both measurements, by calorimetry and magnetometry, are in good agreement. Therefore, the presented AC magnetometer is a suitable way to obtain SAR values of magnetic nanoparticles. [ABSTRACT FROM AUTHOR]

The nonlinear giant magnetoimpedance (GMI) effect was explored as a highly sensitive sensing technology in 3D-printed magnetic encoded systems. Magnetic nanoparticles with low (magnetite, Fe 3 O 4) and high (Co ferrite, Co 0.7 Fe 2.3 O 4) magnetic remanence were embedded (10 wt%) in a polymeric matrix of Polylactic Acid (PLA) and Poly-ε-caprolactone (PCL) and extruded in magnetic filaments to be 3D printed by the Fused Deposition Modelling technique (FDM). Two different geometries were constructed namely, individual magnetic strips and fixed barcoded pieces. The stray magnetic fields generated by the magnetic nanoparticles were detected through the non-linear (second harmonic) GMI voltage using a soft magnetic CoFeSiB wire as the nucleus sensor. The decoding response was analyzed as a function of the magnetization remanence of the nanoparticles, the distance between the individual magnetic strips, and the position (height) of the GMI decoding sensor. It has been shown that modification of the net magnetization direction of each individual fixed strip within the barcode geometry is possible through the application of local external magnetic fields. This possibility improves the versatility of the 3D binary encoding system by adding an additional state (0 without nanoparticles, 1 or −1 depending on the relative orientation of the net magnetization along the strips) during the codifying procedure. [Display omitted] • Low & high remnant 3D printed bar magnets detected by non-linear GMI decoder. • Co ferrite particles detectable at larger heights sensor-piece. • Fe 3 O 4 particles allow better localized detection & simpler magnetization reversal. • Implementation of extra coded state "− 1" related to strip magnetization direction. • Control of the strip's direction allows reuse and magnetic reprogramming. [ABSTRACT FROM AUTHOR]