A turn-on fluorescent probe with a dansyl fluorophore for hydrogen sulfide sensing

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 highly selective and sensitive fluorescence probe based on BODIPY-cyclen for hydrogen sulfide detection in living cells and serum

Hydrogen sulfide (H2S) is a multifunctional gaseous signaling molecule that plays a vital role in several biological processes. In the present study, a BODIPY-based fluorescent probe called 8-[4-((1,4,7,10-tetraazacyclododecane)methyl)phenyl]-4,4-difluoro-1,3,5,7-tetramethyl-4-bora-3a, 4a-diaza-s-indacene (BA-Cyclen)-Cu was designed and synthesized; this probe is a Cu(Ⅱ) complex that uses Cu(Ⅱ) decomplexation to achieve the sensitive and rapid detection of aqueous H2S via the "turn-on" mode. We observed that BA-Cyclen-Cu exhibited good membrane permeability, low toxicity, and lysosome-targeting ability, facilitating H2S detection in living cells. Furthermore, we demonstrated the potential biological applications of the probe by measuring exogenous H2S originating from Na2S and GYY4137, a slow-release donor, and endogenous H2S generated via the catalysis of cystathionine-β-synthase in both normal (H9c2) and cancerous (U87) cells. Moreover, BA-Cyclen-Cu was successfully used to detect exogenous H2S by the external standard method in fetal bovine serum, the serum of a healthy person, and the serum of a patient with liver cancer.

Visual detection of S2- with a paper-based fluorescence sensor coated with CdTe quantum dots via headspace sampling

A simple method was developed in this work for facile and visual detection of S^2- using a paper-based fluorescence (FL) sensor coated with CdTe quantum dots (QDs) by headspace sampling. With the addition of hydrochloric acid, the target S^2- in the liquid phase would transform to H₂ S, which was released to headspace and quenched the FL of CdTe QDs in a linear manner through a gas-solid reaction, with any possible liquid-phase interference avoided. The regular quenching caused by S^2- in analyte solution with increased concentration could be easily observed by the naked eye, and the limit of detection (LOD) for this method was 0.13 μM and 0.93 μM for FL and visual sensing, respectively, comparable or not to that by other sensing probes. A relative standard deviation of 1.2% was accomplished from seven replicated measurements, implying the high reproducibility, and the recovery for the spiked water samples ranging from 94 to 103%, and illustrating the satisfactory reliability of this method. Moreover, the preparation of this paper sensor was facile and did not require any complicated or time-consuming procedures for additional modification or functionalization as for other probes previously reported.

The recent advance of organic fluorescent probe rapid detection for common substances in beverages

The beverage industry is confronted with tremendous challenges in terms of quality assurance. The allowed contents of common ingredients such as copper ions, hydrogen sulfide, cysteine and caffeine are stipulated by various governing bodies, and the beverage industry must ensure that it meets these requirements. Due to its unique advantages of high sensitivity, low cost and relatively low toxicity over high-performance liquid chromatography, atomic absorption spectrometry and nanomaterials, the use of organic fluorescent probes for the rapid detection of beverage contents has become a hot research topic. This review summarizes the detection of common substances in wine, tea, mineral water, milk and other beverages. Furthermore, the preparation of test paper and simple colour comparison are discussed to display the rapid qualitative capability of designed probes. To improve the current state of beverage safety, future trends and strategies for fast organic fluorescent probe detection in the beverage industry are also discussed.

A review: Red/near-infrared (NIR) fluorescent probes based on nucleophilic reactions of H2 S since 2015

The topics of human health and disease are always the focus of much attention. Hydrogen sulfide (H₂ S), as a double-edged sword, plays an important role in biological systems. Studies have revealed that endogenous H₂ S is important to maintain normal physiological functions. Conversely, abnormal levels of H₂ S may contribute to various diseases. Due to the importance of H₂ S in physiology and pathology, research into the effects of H₂ S has been active in recent years. Fluorescent probes with red/near-infrared (NIR) emissions (620-900 nm) are more suitable for imaging applications in vivo, because of their negligible photodamage, deep tissue penetration, and maximum lack of interference from background autofluorescence. H₂ S, an 'evil and positive' molecule, is not only toxic, but also produces significant effects; a 'greedy' molecule, is not only a strong nucleophile under physiological conditions, but also undergoes a continuous double nucleophilic reaction. Therefore, in this tutorial review, we will highlight recent advances made since 2015 in the development and application of red/NIR fluorescent probes based on nucleophilic reactions of H₂ S.