Friedman and his colleagues coated iron oxide nanoparticles with antibodies that bind to a modified version of the temperature-sensitive ion channel TRPV1, which sits on the surface of cells.
They injected these particles into tumours grown under the skins of mice, then used the magnetic field generated by a device similar to a miniature magnetic-resonance-imaging machine to heat the nanoparticles with low-frequency radio waves.
In turn, the nanoparticles heated the ion channel to its activation temperature of 42 °C. Opening the channel allowed calcium to flow into cells, triggering secondary signals that switched on an engineered calcium-sensitive gene that produces insulin. After 30 minutes of radio-wave exposure, the mice's insulin levels had increased and their blood sugar levels had dropped.
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