Fig. 3: Photocapacitive behavior and fast responses of ZST for membrane depolarization induction and action potential generation.

a NeuN and calcein immunostaining in rat cortical neurons. b SEM images and EDS spectra of ZST within the region outlined by the red dashed line on the outer membrane of neurons. c The [Ca²⁺]_i imaging in rat cortical neurons before and after 405 nm laser stimulation (the red box is the laser stimulation area), with the corresponding statistical fluorescence intensity of [Ca²⁺]_i in neurons pre-treated. (−Laser: no laser; +Laser: laser stimulation for 30 s; −ZST: no ZST; +ZST: ZST pre-treatment). d The [Ca²⁺]_i imaging in rat cortical neurons before and after 850 nm fs laser stimulation for 30 s. The results of c and d are shown as mean ± SEM by two-way ANOVA analysis followed by Bonferroni’s post hoc test, N = 30 neurons. e, f The generation of AP on neurons pre-treated by ZST with different 532 nm laser power and pulse duration illumination. g An excitability curve displaying 532 nm laser power and duration combinations that produce AP in neurons (N = 5 neurons; total of N = 30 replicates) to depict the amount of laser power required for AP generation. h Residual plot illustrating the goodness of fit of the hyperbolic fit curve to the data (N = 6 average laser powers for each laser duration used from 5 independent neurons and a total of 30 replicates). i AP firing under varied 532 nm laser stimulation frequencies. j the percentage of failed APs at 130 Hz that the neuron begins to fail to generate 1 AP per pulse of light from 5 independent neurons (The results are shown as mean ± SEM). k An equivalent stimulation circuit. V_P and C_P represent the photo-induced potential and capacitance of ZST; R_J represents the ionic resistance between ZST and outer membrane; E_m, C_m, and R_m represent transmembrane potential, capacitance, and resistance at resting state; V_m is the measured membrane potential. Data are representative of at least three independent experiments with similar results.