Fig. 2: MND-mediated neuronal responses by magnetomechanical stimulation.

SEM images of MNDs (a) and HNDs (b) on the membrane of cultured neurons. c Schematic of magnetic apparatus for fluorescence microscope. right, the dimension of the custom-made coil. d Heat maps of magnetic fields generated by coil. top, FEMM simulation of the coil with 3 A current. bottom, the measured magnetic field inside of the coil with 3 A DC current. Color maps of fluorescence intensity of neurons with MNDs (e) or HNDs (f) application. Magnetic field with 50 mT at 10 Hz was applied for 30 s. g Average traces of Ca²⁺ responses by magnetic field stimulation. Red line, MND group (n = 19/3 (neurons/samples)); Black line, HND group (n = 13/3); Light area, s.e.m. h Maximum change of Ca²⁺ responses in different groups (MND, n = 19/3 (neurons/samples); HND, n = 13/3). ***p < 0.001, Mann-Whitney test. The averaged traces of magnetic induced neuronal Ca²⁺ responses which were stimulated by different frequencies at 1 Hz (i, n = 46/6 (neurons/samples)), 5 Hz (j, n = 30/6), 10 Hz (k, n = 19/6), or 20 Hz (l, n = 18/6). In each frequency, magnetic field intensity was sequentially increased from 10 to 50 mT. The gray areas are s.e.m. The color areas indicate the time periods of magnetic stimulation at 10 (blue), 20 (cyan), 30 (green), 40 (pink), and 50  mT (orange). m The maximum ΔF/F₀ at different conditions (1 Hz, n = 46/6 (neurons/samples)); 5 Hz, n = 30/6; 10 Hz, n = 19/6; 20 Hz, n = 18/6. F = 9.639, p < 0.001 for field intensity, F = 6.155, p < 0.001 for frequencies; F = 1.459, p = 0.11 for interaction of frequencies and intensities. Two-Way ANOVA. ***p < 0.001, Tukey post-hoc test. Error bars represent mean ± s.e.m.