Figure 4. Electrophysiological characterization of bio-interactions of AuNPs.

(A) Schematic of the odor/AuNP delivery and recording setup is shown. An odorant (hexanol 1%) was delivered atop a dry air or a gold nanoparticle aerosol background. The extracellular recording was made to monitor the responses of the principal neurons (or projection neurons; PNs) in the antennal lobe (AL). (B) Top, raster plot showing spiking activity recorded from an ensemble of neurons in the vicinity of the recording electrode. The 4 s duration of odor exposure is shown as a shaded orange box. Bottom, mean spiking activity in 100 ms time segments are shown after averaging across 10 trials. Error bars (shown in light blue) represent ± S.D. over trials. (C) Similar spiking and firing rate plots as in panel (B) but revealing responses of the same set of neurons immediately following the onset of AuNP aerosol exposure. (D) Similar plots as in panel (B,C) but now showing the population PN responses after 2 hours of continuous AuNP aerosol exposure. (E) A comparison of mean ± S.D of spontaneous neural firing rate (baseline spiking activity in a 5 s window without any odor exposure) is shown. Note that spike rates across three conditions are statistically comparable to each other (paired t-test, NS when p > 0.01, n = 10). (F) Similar analyses but comparing activity during the odor puff in all three conditions. Again the differences in spiking activities are insignificant across the three conditions (paired t-test, NS when p > 0.01, n = 10).