Figure 5: Functional testing of the biosensor in Hank’s buffer containing 5 mM Ca2+ reveals that the signal can be amplified by increasing the concentration of calcium ions in the extracellular medium. The p-value for the difference in normalized fluorescence between PP-Orco and the control is less than 0.01 when the VUAA1 concentration is 0.125 mM. The corresponding p-values for the remaining VUAA1 concentrations are below 0.001.
The sensitivity and signal-to-noise ratio of the biosensor was uniformly higher when it was exposed to 5 mM Ca2+ and the TRP-like response was noticeable at all concentrations of VUAA1 that were tested. This observation confirms that the biosensor’s readout can be titrated by changing the concentration of Ca2 in the extracellular medium. A statistically significant difference in normalized fluorescence between PP-Orco and the control is measurable at concentrations of VUAA1 as low as 0.125 mM. The p-value for this statistic is less than 0.01, whereas the p-values for the remaining VUAA1 concentrations are below 0.001.