Figure 17.

Photothermal modulation of spontaneous neural activity. (A) Schematic of repeated GNR-mediated photothermal stimulation of a neuronal network. Neurons were treated with 10 μg/mL of NH2-PEG-GNRs, thenirradiated with an NIR laser multiple times (785 nm, 0–15 mW/mm²). (B) Spike rates of untreated neurons when repeatedly irradiated with an NIR laser (15 mW/mm²). (C) NIR radiation (15 mW/mm²) pike rates of NH2-PEG-GNR-treated neurons that had varying incubation times. (D) A chart of GNR-treated neuron spike rates after the multiple NIR irradiations, shown in (C). One way ANOVA testing (p < 0.0001) showed that n = 264, 74, 97, 99, and 98 at 0 h, 1 h, 3 h, 6 h, and 9 h, respectively. The data point for 0h corresponds to no PNF treatment, as shown in (B). (E) Peri-event histograms and raster plots for GNR-treated neurons, incubated for 9 h, that were irradiated at multiple laser power densities. (F) Chart of spike rate changes from the experiments recorded in (E). One way ANOVA testing was conducted on the neurons tested in (E) for each laser power density. The results were as follows (p < 0.0001): n = 53 at 0 mW/mm², 54 at 3 mW/mm², 54 at 6 mW/mm², 54 at 9 mW/mm², 58 at 12 mW/mm², and 58 at 15 mW/mm². (G) A single trace of spike recording for different NIR irradiation periods (GNR incubation: 9 h, laser power density: 15 mW/mm²). (H) Mean spike rates of GNR-treated neurons before and after NIR irradiation (Data collected from the channels in which neuron activities were completely suppressed during NIR irradiation, two-tailed unpaired t test; p = 0.9064, n = 40 for each bar). Reproduced with permission from [17]. American Chemical Society, 2014.