Magnetothermal Stimulation

Magnetothermal stimulation is the best-validated magnetogenetic mechanism: superparamagnetic iron-oxide nanoparticles injected near or bound to target neurons are exposed to an alternating magnetic field of a few hundred kilohertz, and dissipate heat through Neel and Brownian relaxation (hysteresis loss). The local temperature rise of a few degrees gates a heat-sensitive channel such as TRPV1 expressed in the target cells, producing a calcium influx and depolarisation that is confined to the transgene-bearing, nanoparticle-decorated population.

Heating efficiency is set by the particle's specific loss power, which depends on size, composition, and the field's amplitude and frequency; the safe operating envelope is bounded by the tolerable off-target bulk heating and by field limits on peripheral nerve stimulation. The channel opens on the thermal time constant, so temporal precision is on the order of seconds rather than the milliseconds of optogenetics or electrical stimulation.