Figure 5.

Effect of nanosensor parameter $K_{\text{eq}}$ on performance. (a) Dynamics of three quantal release events (red wedges) imaged using nanosensors for which $K_{\text{eq}}$ varies over 3 orders of magnitude. The first two quantal releases are located 0.2 s apart. Plots of $\text{Δ}F/F_0$ for a 20 Hz frame rate (eq 10) corresponding to each $K_{\text{eq}}$ value are plotted in dashes. At $K_{\text{eq}}=1\mu {\text{M}}^{-1}$, the nanosensor affinity for dopamine is too strong, which adversely affects reversibility. The second release event cannot be resolved. Peak $\text{Δ}F/F_0$ values increase with increasing $K_{\text{eq}}$. At low $K_{\text{eq}}$ values, the nanosensor shows high reversibility but poor sensitivity. (b) Parameter space for reversibility and sensitivity at $r=1,2,5$, and 10 μm from release site corresponding to a 20 Hz imaging frame rate. High dopamine concentrations proximal to the release site yield high percent nanosensor sensitivity. However, maintaining good nanosensor reversibility suffers proximal to the release site.