Fig. 2: Investigation of the impact of different TDN-modified biosensing interfaces.

a PAGE electrophoresis of TDN-13, TDN-17, TDN-26. 5% page, 110 V, 70 min, the whole process below 10 °C in ice-water bath, dyed for 15 min in room temperature, M referring to DNA marker, n = 3 independent experiments, repeated time=3 for each independent experiment. b AFM image of TDN-17, n = 3 independent experiments, repeated time = 3 for each independent experiment. c Comparison of the response signals in the presence of different concentrations of target cfDNA with TDNs of different heights and without TDNs in simulated ISF (PBS, pH = 7.4, 37 °C, 0.01 M), n = 3 independent experiments, repeated time=3, data presented as the mean values ± standard deviations (SD). d Dynamic curves of real-time monitoring target cfDNA by TDN-17 (height of 5.8 nm)-mediated biosensing interface on a microelectrode under reverse iontophoresis (10 V, PBS, pH = 7.4, 37 °C, 0.01 M). e Calibration curve of I response versus target concentration. Data are presented as the mean values ± SDs, n = 3 independent experiments. f Slope values of the curves collected from Fig. 2d calculated by differentiation using two-way ANOVA: *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001, p value of 0.000477, 0.00000598, 0.00000752, 0.00000842 for 0.3, 3, 30, 300 fM groups respectively, data presented as the mean values ± SDs, n = 3 independent experiments.