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Alkaline phosphatase (ALP) is a family of enzymes involved in the regulation of important biological processes such as cell differentiation and bone mineralization. Monitoring the activity of ALP in serum can help diagnose a variety of diseases including bone and liver diseases. There has been growing interest in developing new chemical tools for monitoring ALP activity in living systems. Such tools will help further delineate the roles of ALP in biological and pathological processes. Previously reported fluorescent probes has a number of disadvantages that limit their application, such as poor selectivity and short-wavelength excitation. In this work, we report a new two-photon fluorescent probe (TP-Phos) to selectively detect ALP activity. The probe is composed of a two-photon fluorophore, a phosphate recognition moiety, and a self-cleavable adaptor. It offers a number of advantages over previously reported probes, such as fast reaction kinetics, high sensitivity and low cytotoxicity. Experimental results also showed that TP-Phos displayed improved selectivity over DIFMUP, a commonly utilized ALP probe. The selectivity is attributed to the utilization of an ortho-functionalised phenyl phosphate group, which increases the steric hindrance of the probe and the active site of phosphatases. Moreover, the two-photon nature of the probe confers enhanced imaging properties such as increased penetration depth and lower tissue autofluorescence. TP-Phos was successfully used to image the endogenous ALP activity of hippocampus, kidney and liver tissues from rat. [ABSTRACT FROM AUTHOR]

Thiophenols are widely utilized for producing pesticides, polymers and pharmaceuticals. Studies have shown that prolonged exposure of human to thiolphenol can result in serious health problems such as significant damage of the central nervous system. Herein, we have developed a novel turn-on two-photon fluorescent probe TP-ASH for selective and sensitive detection of thiophenols. We first constructed a new two-photon dye by connecting a coumarin fluorophore and a naphthalene fluorophore through 2,5- disubstituted-1,3,4-oxadiazole ring to afford d -π-A-π- d -structure. Fluorescent studies showed that this new dye possess large two-photon active absorption across-section (250 GM) and high fluorescence quantum yield (0.85). Encouraged by the results, we proceeded to conjugate this novel dye to a thiophenol recognition moiety, 4-dinitrobenzene-ether (DNB). The resulting probe displayed high selectivity towards thiophenols over their similar analogues, aliphatic thiols. The probe also exhibited high sensitivity, with a detection limit of 6.7 nM and a fluorescence enhancement of 163-fold. In addition, we have successfully applied the probe for two-photon imaging studies of thiphenols in living cells and mice tissues. We envision that the probe will add useful tools in detecting thiophenols in environmental samples and biological systems. [ABSTRACT FROM AUTHOR]

Intracellular pH plays a pivotal role in various biological processes. Herein, we adopted the through bond energy transfer (TBET) strategy to design a unique type of ratiometric two-photon fluorescent probe for imaging of lysosomal pH in live cells and tissues, termed Np-Rh-Lys. Specifically, a two-photon fluorophore (D-π-A-structured naphthalimide derivative) and a rhodamine B fluorophore were directly connected, and dimethylamino moiety served as a lysosomal targeting-group. The experiments demonstrate new probe Np-Rh-Lys was a reliable and specific probe for labeling lysosomes in living cells with two well-resolved emission peaks separated by 80 nm, and which showed high ratiometric imaging resolution and deep-tissue imaging depth over 180 μm, we thus may expect the new platform prompt the development of a wide variety of ratiometric two-photon fluorescent probes application in biological systems. [ABSTRACT FROM AUTHOR]