A Ratiometric Near-Infrared Fluorescent Probe for Quantification and Evaluation of Selenocysteine-Protective Effects in Acute Inflammation

Selenocysteine (Sec) is a primary kind of reactive selenium species in cells whose antioxidant roles in a series of liver diseases have been featured. However, it is difficult to determine Sec in living cells and in vivo due to its high reactivity and instability. This work reports a ratiometric near-infrared fluorescent probe (Cy-SS) for qualitative and quantitative determination of Sec in living cells and in vivo. The probe is composed of heptamethine cyanine fluorophore, the response unit bis(2-hydroxyethyl)disulfide, and the liver-targeting moiety D-galactose. Based on a detection mechanism of selenium-sulfur exchange reaction, the concentrations of Sec in HepG2, HL-7702 cells, and primary mouse hepatocytes is determined as 3.08 +/- 0.11 x 10(-6) M, 4.03 +/- 0.16 x 10(-6) M and 4.34 +/- 0.30 x 10(-6) M, respectively. The probe can selectively accumulate in liver. The ratio fluorescence signal of the probe can be employed to quantitatively analyze the fluctuation of Sec concentrations in cells and mice models of acute hepatitis. The experimental results demonstrate that Sec plays important antioxidant and anti-inflammatory roles during inflammatory process. And the levels of intracellular Sec have a close relationship with the degree of liver inflammation. The above imaging detections make this new probe a potential candidate for the accurate diagnosis of inflammation.