Xiaoqiang Chen

Enhanced response speed and selectivity of fluorescein-based H2S probe via the cleavage of nitrobenzene sulfonyl ester assisted by ortho aldehyde groups.

In this work, we developed three fluorescent probes (F-1, F-2, and F-3) based on fluorescein, mono-formylated fluorescein, and bis-formylated fluorescein for hydrogen sulfide (H2S) detection. The probe F-3, which bears two aldehyde groups, exhibited the fastest response. This fast response is attributed to the ortho effect of the aldehyde group, which enables fast nucleophilic addition of H2S to an aldehyde group and subsequent intramolecular thiolysis of dinitrophenyl ether. In addition, the aldehyde groups on F-3 react with biothiols (e.g., cysteine, homocysteine) to form thiazolidine diastereomers, which suppress the fluorescence of fluorescein. The introduction of two aldehyde groups also resulted in high selectivity of F-3 towards H2S. Furthermore, good linearity was observed between F-3 fluorescence intensity at 510nm and H2S concentration in the range of 0-10µM. F-3 exhibited a detection limit as low as 0.024μM. Confocal laser scanning micrographs of HeLa cells incubated with F-3 confirmed that F-3 is cell-permeable and can successfully detect H2S in living cells.

Recent Progress in the Development of Fluorometric Chemosensors to Detect Enzymatic Activity

Enzymes are a class of macromolecules that function as highly efficient and specific biological catalysts requiring only mild reaction conditions. Enzymes are essential to maintaining life activities, including promoting metabolism and homeostasis, and participating in a variety of physiological functions. Accordingly, enzymatic levels and activity are closely related to the health of the organism, where enzymatic dysfunctions often lead to corresponding diseases in the host. Because of this, diagnosis of certain diseases is based on the levels and activity of certain enzymes. Therefore, rapid real-time and accurate detection of enzymes in situ is important for diagnosis, monitoring, clinical treatment, and pathological studies of disease. Fluorescent probes have unique advantages in terms of detecting enzymes, including being simple to use in highly sensitive and selective real-time rapid in-situ non-invasive and highly spatial resolution visual imaging. However, fluorescent probes are most commonly used to detect oxidoreductases, transferases, and hydrolases due to the processes and types of enzyme reactions. This paper summarizes the application of fluorescent probes to detect these three types of enzymes over the past five years. In addition, we introduce the mechanisms underlying detection of these enzymes by their corresponding probes.