A near-infrared fluorescent probe based FRET for ratiometric sensing of H 2 O 2 and viscosity in live cells.

Hydrogen peroxide (H2 O2 ) and viscosity play vital roles in the cellular environment as signaling molecule and microenvironment parameter, respectively, and are associated with many physiological and pathological processes in biological systems. We developed a near-infrared fluorescent probe, CQ, which performed colorimetric and ratiometric detection of H2 O2 and viscosity based on the FRET mechanism, and was capable of monitoring changes in viscosity and H2 O2 levels simultaneously through two different channels. Based on the specific reaction of H2 O2 with borate ester, CQ exhibited a significant ratiometric response to H2 O2 with a large Stokes shift of 221 nm, a detection limit of 0.87 μM, a near-infrared emission wavelength of 671 nm, a response time of 1 h, a wide detection ranges of 0.87-800 μM and a high energy transfer efficiency of 99.9 %. CQ could also recognize viscosity by the TICT mechanism, and efficiently detect viscosity changes caused by food thickeners. More importantly, CQ could successfully detect endogenous/exogenous H2 O2 and viscosity in live HeLa cells, which was expected to be a practical tool for detecting H2 O2 and viscosity in live cells.