Juan Ou-Yang

Facile and Sensitive Near-Infrared Fluorescence Probe for the Detection of Endogenous Alkaline Phosphatase Activity In Vivo

Alkaline phosphatase (ALP) is an essential enzyme and widely distributes in a variety of tissues. To date, various nanomaterial and small-molecule fluorescent probes for ALP have been constructed successfully, but the emission wavelengths of these probes are in the ultraviolet or visible range, which is not beneficial for bioimaging. Herein, a hemicyanine-based near-infrared (NIR) fluorescent probe named CyP is first synthesized and used to detect ALP activity. The characteristics of probe CyP are as follows: (1) The probe possesses a facile structure, which can be obtained by easy synthetic steps. (2) The fluorescence emission of the sensing system is at 738 nm belonging to NIR region, which is suitable for bioimaging in vivo. (3) The probe exhibits high sensitivity to ALP with 10-fold fluorescence enhancement and low detection limit (0.003 U/mL) can match the level of ALP in vivo. (4) The fluorescent change of the probe is attributed to the fact that ALP-catalyzed cleavage of the phosphate group in CyP induces the transformation of CyP (fluorescence off) into CyOH (fluorescence on), which is proved by HPLC, 31P NMR, MS, and DFT calculation. (5) The NIR fluorescent probe is applied for the detection of endogenous ALP activity in various biological samples such as cell, tissue, and living animal with satisfactory results.

A Dual-Response Fluorescent Probe for the Detection of Viscosity and H2S and Its application in Studying Their Cross-Talk Influence in Mitochondria

Intracellular viscosity is an essential microenvironmental parameter and H2S is a critical gaseous signaling molecule, which are both related to various physiological processes. It is reported that the change of viscosity and an imbalance of H2S production in the mitochondria are both associated with overexpression of amyloid betapeptide (Aβ), which is thought to play a central role in the pathogenesis of Alzheimers disease (AD). However, to our best knowledge, no fluorescent probe is found for dual detection of mitochondrial viscosity and H2S. Herein, a dual-response fluorescent probe (Mito-VS) is designed and synthesized to monitor the level of viscosity and H2S, respectively. Mito-VS itself is nonfluorescent due to a free intramolecular rotation between dimethylaniline and pyridine. After the increase of viscosity, the rotation is prohibited and an intense red fluorescence is released. Upon the addition of H2S, the probe can react with H2S to form compound 3 and a strong green fluorescence can be observed. Moreover, the probe possesses a good mitochondrion-targeting ability and is applied for imaging the change of viscosity on the red channel and visualizing the variation of exogenous and endogenous H2S concentration on the green channel in mitochondria. Most importantly, the probe is capable of studying the cross-talk influence of viscosity and H2S in mitochondria, which is very beneficial for knowing the pathogenesis of AD.

Detecting and Imaging of γ-Glutamytranspeptidase Activity in Serum, Live Cells, and Pathological Tissues with a High Signal-Stability Probe by Releasing a Precipitating Fluorochrome

γ-Glutamytranspeptidase (GGT) is a significant tumor-related biomarker that overexpresses in several tumor cells. Accurate detection and imaging of GGT activity in serum, live cells, and pathological tissues hold great significance for cancer diagnosis, treatment, and management. Recently developed small molecule fluorescent probes for GGT tend to diffuse to the whole cytoplasm and then translocate out of live cells after enzymatic reaction, which make them fail to provide high spatial resolution and long-term imaging in biological systems. To address these problems, a novel fluorescent probe (HPQ-PDG) which releases a precipitating fluorochrome upon the catalysis of GGT is designed and synthesized. HPQ-PDG is able to detect GGT activity with high spatial resolution and good signal-stability. The large Stokes shift of the probe enables it to detect the activity of GGT in serum samples with high sensitivity. To our delight, the probe is used for imaging GGT activity in live cells with the ability of discriminating cancer cells from normal cells. Whats more, we successfully apply it for pathological tissues imaging, with the results indicating that the potential application of HPQ-PDG in histopathological examination. All these results demonstrate the potential application of HPQ-PDG in the clinic.

Mitochondria-targeted near-infrared fluorescent probe for the detection of carbon monoxide in vivo

Carbon monoxide is a critical gasotransmitter in the body and related with mitochondrial respiration. To date, various fluorescent probes for CO have been well proposed, but two main problems remain. One is that most of the probes are not mitochondria-targeting, even if the probes claim to be able to detect CO in living cells. The other is that the probes for CO display excitation and emission within the ultraviolet or visible range, which hinders their applications in vivo. Herein, a hemicyanine-based near-infrared (NIR) fluorescent probe named CyAPC is first synthesized and used to detect mitochondrial CO. The characteristics of probe CyAPC are as follows: (1) The fluorescence emission of the sensing system is at 736 nm belonging to NIR region, which is suitable for bioimaging in vivo. (2) CyAPC, a positively charged molecule, would have a high tendency to localize in mitochondria of cells. (3) The fluorescence change of the probe is attributed to the fact that CO with Pd2+ induced cleavage of the allyl formate group from the probe and CyAPC (fluorescence off) is transformed into CyOH (fluorescence on), which is proved by HPLC, MS and DFT calculation. (4) The NIR fluorescent probe is applied for the detection of exogenous and endogenous CO in various biological samples such as cell, tissue and in vivo with satisfactory results.