Development of a Silicon-Rhodamine Based Near-Infrared Emissive Two-Photon Fluorescent Probe for Nitric Oxide.

Two-photon (TP) fluorescent probes are potential candidates for near-infrared (NIR) imaging which holds great promise in biological research. However, currently, most TP probes emit at wavelength <600 nm, which impedes their practical applications. In this work, we explored the TP properties of a silicon-rhodamine (SiR) derivative and hence developed the first SiR scaffold based "NIR-to-NIR" TP probe (SiRNO) for nitric oxide (NO). SiRNO exhibited high sensitivity and specificity, as well as fast response for NO detection. It was able to track the subtle variation of intracellular NO content in live cells. Owing to the NIR excitation and emission, SiRNO enabled the detection of NO in situ in the xenograft tumor mouse model, revealing the NO generation during the tumor progression. This work indicates that SiR can be an ideal platform for the development of NIR emissive TP probe and may thus promote the advancement of NIR imaging.