Optode-based fluorescence nanosensors have recently been employed to detect ions in physiological environment. As commercially available fluorescent indicator dyes tend to leak during intracellular measurements and have limited wavelength choices, we complement the current toolbox by presenting a modular ratiometric nanosensor platform for monitoring intracellular ion transients. The selective recruitment of physiological ions in the nanosensor promotes the deprotonation of the pH-sensitive dye which provides an optical readout of targeted ion levels in living cells. This ratiometric detection scheme has demonstrated superb selectivity, fully reversible response, and ability to fine-tune to physiological sensing range in the intracellular environment. Here we monitored sodium (Na<sup>+</sup>) ion dynamics in isolated dorsal root ganglion neurons using ion-selective fluorescent nanosensors during both pharmacological and electrical stimulations. The nanosensors exhibits optimal sensing range around 10 mM in line with intracellular sodium level, and are 25-times more responsive to sodium than potassium, the main interfering ion. Moreover, the pH sensitive-dye (ETH 5350) in the sensor offers advantageous photophysical properties such as longer excitation wavelength and higher quantum yield (0.25) compared with currently used ratiometric dye SBFI which requires excitation at UV range. While conventional indicators can improve individual aspects of indicator performance such as dynamic sensing range, wavelength, quantum yield and ratiometric measurements, the use of nanosensor platform can achieve combined benefits by addressing these issues simultaneously. Overall, this sensing platform offers a new analytical tool and opens up new opportunities for probing intracellular ion dynamics on the single cell level.

Intracellular ion monitoring in neurons tracked by modular ratiometric nanosensors

256th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.