Development of a two-photon fluorescent probe for imaging hydrogen sulfide (H2S) in living cells and zebrafish

Activity-Based Fluorescent Probes for Hydrogen Sulfide and Related Reactive Sulfur Species

Hydrogen sulfide (H2S) is not only a well-established toxic gas but also an important small molecule bioregulator in all kingdoms of life. In contemporary biology, H2S is often classified as a "gasotransmitter," meaning that it is an endogenously produced membrane permeable gas that carries out essential cellular processes. Fluorescent probes for H2S and related reactive sulfur species (RSS) detection provide an important cornerstone for investigating the multifaceted roles of these important small molecules in complex biological systems. A now common approach to develop such tools is to develop "activity-based probes" that couple a specific H2S-mediated chemical reaction to a fluorescent output. This Review covers the different types of such probes and also highlights the chemical mechanisms by which each probe type is activated by specific RSS. Common examples include reduction of oxidized nitrogen motifs, disulfide exchange, electrophilic reactions, metal precipitation, and metal coordination. In addition, we also outline complementary activity-based probes for imaging reductant-labile and sulfane sulfur species, including persulfides and polysulfides. For probes highlighted in this Review, we focus on small molecule systems with demonstrated compatibility in cellular systems or related applications. Building from breadth of reported activity-based strategies and application, we also highlight key unmet challenges and future opportunities for advancing activity-based probes for H2S and related RSS.

A novel fluorescent probe for cascade detection of hydrogen sulfide and hypochlorous acid and its application in bioimaging

Herein we developed a cascade detection mode for the detection of HS- and ClO- by the novel probe NM-Cl bearing a conjugating naphthalene-dicyanoisophorone unit. The probe displayed sensitive and remarkable fluorescent enhancement in response to HS-, but not to other analytes. The mixture of probe and HS- constructed a specific sensing system for ClO- by fluorescent quenching response. The mechanism studies indicated that the successive reacting of HS- substitution Cl atom in probe and then addition of ClO- facilitation a thiofuran ring-forming induced differentiated fluorescence emission. This study provides a novel mechanism for the detection of HS- and ClO-, the imaging of cell and living animal further indicating the good application prospects of the probe in biosensing and bioimaging.

A Novel DNBS-based Fluorescent Probe for the Detection of H2S in Cells and on Test Strips

Hydrogen sulfide (H2S) plays a key role in the physiology and pathology of organisms, and H2S in the environment is easily absorbed and harmful to health. It is of great significance to develop a probe with good selectivity, high sensitivity and good stability that can detect hydrogen sulfide inside and outside organisms. In this work, we designed a novel "turn-on" fluorescent probe CIM-SDB for the detection of H2S. The probe CIM-SDB used indene-carbazole as the fluorophore and 2,4-dinitrobenzenesulfonyl as the recognition site. The probe CIM-SDB exhibited high selectivity and sensitivity to H2S (detection limit as low as 123 nM). Moreover, the probe CIM-SDB was successfully applied to the detection of intracellular exogenous and endogenous H2S, and the test strips prepared by the probe CIM-SDB could realize the convenient and rapid detection of H2S.

A multi-functional fluorescent probe for visualization of H2S and viscosity/polarity and its application in cancer imaging

As an important endogenous gasotransmitter, hydrogen sulfide (H2S) plays a critical role in various physiological functions and has been regarded as a biomarker of cancer due to its overexpression in cancer cells. In addition, the early stages of cancer are often accompanied by abnormalities in the intracellular microenvironments, and distinguishing between cancer cell/tissues and normal cell/tissues is of great significance to the accuracy of cancer diagnosis. However, deep insights into the simultaneous detection of H2S and viscosity/polarity variations in cancer cells/tissues are rarely reported. In this work, we designed and synthesized a mitochondria-targeting fluorescent probe PDQHS, which exhibits high selectivity for H2S with an emission peak around 632 nm and excellent response (17-fold) to viscosity/polarity beyond 706 nm. Meanwhile, PDQHS shows good biocompatibility and can specifically accumulate into mitochondria. Using PDQHS, the visual distinguishing of cancer cells from normal cells was achieved via dual-channel detection of H2S and viscosity/polarity. More importantly, PDQHS has been successfully applied to visualize endogenous and exogenous H2S in living cells and tumor tissue. Obviously, compared to the detection of a single biomarker, monitoring multiple biomarkers simultaneously through dual-channel response is conducive to amplifying the detection signal, providing a more sensitive and reliable imaging tool in the tumor region, which is beneficial for cancer prediction.

A Highly Selective Fluorescent Probe for Hydrogen Sulfide and its Application in Living Cell

A new Near-infrared fluorescent probe for hydrogen sulfide detection was synthesized by employing dicyanoisophorone based fluorescence dye as a fluorophore and methyl 3-(2-(carbonyl)phenyl)-2-cyanoacrylate group as the response unit. The Probe DCI-H2S showed a long emission wavelength (λem = 674 nm). Based on the H2S-induced addition-cyclization of deprotecting methyl 3-(2-(carbonyl)phenyl)-2-cyanoacrylate group, the probe DCI-H2S showed high selectivity, sensitivity and response speed toward hydrogen sulfide under room temperature. These numerous advantages of the probe DCI-H2S make it to potentially detect endogenous hydrogen sulfide in living organisms.

A new lysosome-targeted Cys probe and its application in biology and food samples

Cysteine (Cys) is a sulfur-containing amino acid that plays an important role in living systems. The most common way to supplement the body with exogenous Cys is through the consumption of Cys-rich foods. Therefore, it is important to detect and analyze Cys in living systems and food samples. However, most of the Cys fluorescent probes developed so far are limited to the detection of the cellular environment only, and very few probes can take into account the detection of Cys in plant roots and food samples. In this paper, a novel fluorescent probe LN-NCS targeting the detection of Cys in lysosomes was designed and synthesized by modifying the naphthalimide fluorophore. The probe LN-NCS has a large Stokes shift (140 nm), low cytotoxicity, low detection limit (16.3 nM), and high selectivity, and probe LN-NCS reacts with Cys to produce the compound LN-NH2 with good fluorescence quantum yield (Ф = 0.81). Probe LN-NCS can be used to detect Cys in cells, zebrafish, plant roots, food samples, and environmental water samples. In addition, by modeling cellular inflammation, we have demonstrated that probe LN-NCS can detect changes in Cys concentration induced by cellular inflammation, providing a potential tool to better study the cellular inflammatory environment.

A novel fluorescent probe based on naphthimide for H2S identification and application

In view of the superior chemical activity of selenoether bond (-Se-) and the excellent optical properties of naphthimide, a novel fluorescent probe (NapSe) with near-rectangular structure, which contains double naphthimide fluorophores linked by selenoether bond, is designed for specific fluorescence detection of hydrogen sulfide (H2S). NapSe has excellent optical properties: super large Stokes Shift (190 nm) and good stability in a wide pH range. The selectivity of NapSe fluorescence detection of H2S is high, and displays excellent "turn-on" phenomenon and strong anti-interference. And the fluorescence intensity increased obviously, reaching 42 times. The time response of probe NapSe is very rapid (3 min) compared with other fluorescence probes that respond to H2S. It shows high sensitivity by calculating the detection limit (LOD) as low as 5.4 μM. Notably, the identification of H2S by probe NapSe has been successfully applied to the detection of test paper and the detection of exogenous and endogenous fluorescence imaging of MCF-7 breast cancer cells.