Figure 2.

Photosensitivity of DRG neurons mediated by 25 × 94 nm AuNRs. All laser pulses were at 785 nm. (A) Given here are membrane voltage responses of a single cell to depolarizing current (1 nA, 1 ms) (left traces) and a 5 μJ laser pulse (5 mW, 1 ms) (right traces) delivered over a series of 37 trials. In recording sweeps where current injection failed to produce an AP, the laser pulse similarly failed to generate an AP. At the moment of laser pulse delivery, the membrane was clamped at I_m = 0 A by the patch amplifier; all of the observed depolarizing current was thus due to the optocapacitive effect. Occurrences of subthreshold current-injection-induced and laser-pulse-induced responses are attributable to intertrial fluctuations. (B) Given here are pipette current injection-induced (black trace) and laser pulse-induced (red trace) APs recorded within the same 3-s trial. (C) Shown here are responses to 5.5-mW laser pulses of durations ranging from 0.1 to 1.7 ms in 0.1-ms increments. AP threshold was reached at a duration of 0.9 ms. (D) Given here are responses to 1-ms pulses of differing power (1.6–5 μJ). (E) Given here is a log-log plot of E_Th (minimal pulse energy required for AP generation) versus pulse duration (Δt). Data were obtained from a total of 17 DRG neurons. (Fitted line) Given here is the power law relation E_Th = aΔt^b, with values of coefficient a and exponent b shown in the figure. (Insets) Given here are representative APs elicited by pulses of 1 μs (76.5 mW, 76 nJ) and 1 ms (5.2 mW, 5.2 μJ). To see this figure in color, go online.