Figure 3: Spontaneous electrical activity of primary hippocampal neurons cultured onto bioorganic active interfaces.

(a) The resting membrane potential of neurons cultured on either poly-L-lysine (PLL)-treated ITO/rr-P3HT:PCBM devices (red, n=24) or control glass substrates covered only with ITO and PLL (black, n=16) was measured (t-test, P=0.506). (b) Analysis of the frequency (left; t-test, P=0.736, n=10) and amplitude distribution (right; n=6, bins 20 pA) of spontaneous excitatory postsynaptic currents (EPSCs). (c) Example of whole-cell recordings from neurons cultured on either polymer (red) or control (black) substrates. The analysis of neuronal firing rates in ITO/rr-P3HT:PCBM devices (red, n=10) and control substrates (black, n=10) did not show any significant difference (left, t-test, P=0.780). (d) Network mean firing rates (MFRs) computed with multielectrode array devices. Sample traces show a representative example of extracellular spikes recorded in the presence (red) or absence (black) of polymer deposition. Statistical analysis (t-test, P=0.843, n=9) did not show any difference between the two conditions. Scale bars, 30 μm. Box plot limits represent the 25th and 75th percentile and whiskers represent the outliers (coefficient 1.5) of the distribution. The mean (square), maximum and minimum values of the distribution are also shown.