Figure 1.

Design of multiplexed control of cell signaling using selective magnetothermal stimulation. (a) and (b) Doping of cobalt into Fe₃O₄ results in higher magnetic anisotropy, making cobalt ferrite MNPs magnetically harder compared to Fe₃O₄. (c) and (d) Schematic representation of multiplexed magnetothermal control of cell signaling using two different MNP ensembles that respond selectively to paired AMF conditions. (c) A high-amplitude, low-frequency AMF is sufficient to access major hysteresis loops for both MNPs, with the major hysteresis loops of Co_xFe_3-xO₄ MNPs inherently larger, causing them to heat preferentially. (d) An AMF with low amplitude and high frequency results in major hysteresis loops only for less coercive MNPs (Fe₃O₄), and minor loops for Co_xFe_3-xO_4. The MNPs only dissipate heat effectively when they are exposed to their respectively paired AMF conditions, triggering the opening of the heat sensitive TRPV1 ion channels exogenously expressed in the HEK cells. Calcium ions flow into the cells through the activated TRPV1 channels and bind to GCaMP6s indicators, producing an increase in green fluorescence.