Wide-Range Fluorescent pH Sensor

A new molecular sensor that matches the pH range of glass pH electrodes could be used for measuring pH in biological cells and microfluidic devices (J. Am. Chem. Soc., DOI: 10.1021/ja0686514).

The sensor, designed by A. Prasanna de Silva at Queen's University, Belfast, Northern Ireland, and coworkers, consists of four disubstituted anthracenes that fluoresce in parallel over different pH ranges by a mechanism of photoinduced electron transfer. The anthracenes have a fluorophore-spacer-receptor design that uses the same fluorophore and spacers but different receptors with different proton-binding strengths.

The pH of a solution containing equal concentrations of all four components is directly proportional to the summed fluorescence intensities of the components at a specific wavelength. As such, this sensor works in an analog mode rather than a digital one. The sensor measures pH across nearly 10 pH units, whereas the range of classical molecular sensors is around two units.

The team suggests that the design could be used to construct wide-range sensors that target sodium and other species of chemical and biological interest.