Analyte regeneration near-infrared fluorescent probe for endogenous formaldehyde detection in living cells and in vivo

Reaction-based fluorescent probes have proved to be promising tools for endogenous formaldehyde (FA) analysis. Among them, analyte regeneration fluorescent probes have attracted much attention due to their ability to maintain FA homeostasis in imaging analysis, but remain to be explored. Herein, we proposed a novel analyte regeneration near-infrared fluorescent probe Cy-MB for endogenous FA detection. Cy-MB was developed on the basis of hemicyanine-based NIR probe CyOH via connecting a 2-(methylamino)benzoate acid. The 2-(methylamino)benzoate in Cy-MB act not only as a fluorescence quenching group, but also a FA regeneration substrate. Such an analyte regeneration NIR probe can be specifically activated by endogenous FA, resulting in a significant fluorescence signal turn on and accompanied by FA regeneration. Probe Cy-MB possesses good analytical performance such as high selectivity and sensitivity toward FA with a detection limit at 0.67 μM. Furthermore, Cy-MB was successfully applied to image endogenous FA in cancer cells and tumor-bearing mice. Additionally, mass spectrometry imaging (MSI) was further performed to qualitatively identified the spatial distribution of the FA activation products of Cy-MB on molecules level in tumor and major organs of mice. We envision that Cy-MB will provide a widespread application in precise imaging of endogenous FA in biosystems.