Figure 4. Spatially targeted heating is achieved using a strong space-variant static gating field.

(a) MnZnSPIONs (100 mg mL⁻¹) heat ΔT = 55°C from baseline in the presence of a 350 Oe, 500 kHz alternating magnetic field. Heating can be suppressed to ΔT ~ 2°C with a strong (4000 G) static field. (b) In the presence of an alternating magnetic field, heat generated scales linearly with MnZnSPION concentration. At all concentrations, this effect can be suppressed with a strong (4000 G) static field. (c) At the center of the static magnetic configuration (dark blue), a sample of 100 mg mL⁻¹ MnZnSPIONs heats to T = 50°C, while the temperature is maintained at T < 25°C at the edges (light blue), demonstrating spatially targeted induction of heating. (d) Meanwhile, the temperature of a sample of water is maintained at T < 20°C, regardless of whether it is placed at the center (dark blue) or edge (light blue). T_phys = physiological temperature, 37°C; T_trans = liposomal transition temperature, 42°C. n = 3.