Reversible Ratiometric Probe Combined with Time-gated Method for Accurate in Vivo Gastrointestinal pH Sensing.

Fluorescence sensing exhibits advantages of real-time, non-invasive, convenient, and less impact on the original environment for in vivo detection. Here a reversible time-gated ratiometric in vivo detection method that could eliminate the interferences from probe amount, photon scattering and absorption is proposed. Correspondingly, the composite probe must be able to reversibly respond to changes in the microenvironment and emit two luminescent signals at the same working wavelength, but different lifetimes. Benefitting from the reversible detection mechanism, the probes could be used to monitor a dynamic biological process and the ratio signal value could be determined only by the concentration of analytes but independent of the probe concentration. And benefitting from the same working wavelength, the read-out errors from photon absorption and scattering could be minimized. This method is very suitable for in vivo detection in which the probe distribution and depth is unknown and variable. As a typical model, the different pH values in the gastrointestinal area and pH changes caused by drugs and fasting are successfully monitored.