An "off-on" fluorescent probe for imaging pyruvic acid in living systems.

Pyruvic acid (PA) is an α-keto acid which exert important biological and pathological functions. The current PA profiling assays are mainly based on the ultraviolet spectroscopy and electrochemical biosensor, requiring killing cells and destroying tissues which limit their application in living cells. Optical imaging provides nondestructive powerful and detective tools to better understand the physiological and pathological role of PA in living systems. However, as far as we know, none of"off - on" PA fluorescent sensor has been developed. Herein, we reported a PA recognition reaction that arylhydroxylamine group could be selectively reduced to acetylamide group by PA. With this recognition reaction, a fluorescence probe (FPA) based on the photoinduced electron transfer (PET) pathway was designed, synthesized and could release strong fluorescence at 447 nm. We proved that FPA could detect PA in aqueous solution, living cells, Caenorhabditis elegans and the roots of Arabidopsis thaliana with good selectivity and sensitivity as low as 0.42 μM. In addition, we successfully using probe FPA to study the intracellular PA production pathway in cells and evaluated its physiological level in Arabidopsis roots at different growth stages. The results show that the physiological level of PA in Arabidopsis thaliana roots is closely associated with their growth stages, which indicated that PA might act as a carbon source and related growth signaling molecule to promote plant growth and root elongation. Therefore, we expect probe FPA to be a powerful tool to better understand the physiological and pathological role of PA.