| Summary: | Magnetic nanoparticles (MNPs) provide several mechanisms for wireless neuromodulation. MNPs under applied AC magnetic fields (AMFs) exhibit hysteresis loss, which can activate heat-sensitive ion channels such as TRPV1. This magnetothermal modulation requires AMFs with peak field strengths of up to 40 kA/m and frequencies of up to 580 kHz. While air–gap magnetic cores can achieve the necessary field parameters, their small size limits them to in–vitro experiments. A 10 cm coreless solenoid design generates the desired field parameters and is suitable for in–vivo experiments but requires several kilowatts of power. Here, we show the construction of a resonant tank inverter capable of delivering 6000 Watts of power at 600 V and 10 A to the tank circuit and generating the requisite AMF field strength and frequency inside the coil.
As a first experiment, we use the apparatus to demonstrate wireless, magnetothermal modulation of dorsal root ganglia (DRG) explants, sensory neuronal structures that are a critical target for nerve therapy. Calcium influx into neurons plays a key role in many processes necessary for axonal regeneratiton. Using magnetothermal modulation, we stimulate calcium uptake into DRG cells via TRPV1 ion channels, which are endogenously expressed and heat sensitive. By adjusting the pulse pat-tern of magnetic stimulation, we find the optimal conditions for inducing neurite outgrowth in DRG cultures.
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