A hemicyanidin-based NIR fluorescent probe for detection of H2S and imaging study in cells and mice

A novel structurally modified isophorone fluorescent probe for H2S detection

Hydrogen sulfide (H2S) has a comprehensive contribution to the normal operation and stability of organisms and is also present in environmental water samples and food deterioration. Thus, it is exceedingly promising and significant to develop a highly sensitive detection technique for tracing H2S. Inspired by this, we designed and synthesized a new fluorescent probe 2-[3-[2-[3-bromo-4-(2,4- dinitrobenzenesulfonate)] ethenyl]-5,5-dimethyl-2-cyclohexen-1-ylidene]propanedinitrile (SP-Br) for hydrosulfide ion detection by introducing bromine atom. Compared with reported H2S probes based on the same fluorescent parent, SP-Br has longer fluorescence emission (λem = 670 nm), shorter response time (3 min), lower detection limit (149 nM), and wider detection range (0-30 nM). SP-Br can emit weak yellow fluorescence, and the emission intensity at 670 nm is considerably enhanced in the presence of hydrosulfide ions. The identification mechanism of hydrosulfide ion by SP-Br was verified by high-resolution mass spectrometry, fluorescence, and UV-vis absorption spectroscopy. In addition, SP-Br has been successfully applied to the monitoring of actual water samples and beer samples and has certain development prospects and value in the fields of environmental pollution and food quality analysis.

Research progress of hydrogen sulfide fluorescent probes targeting organelles

Hydrogen sulfide (H2S) is implicated in numerous physiological and pathological processes in living organisms. Abnormal levels of H2S can result in various physiological disorders, highlighting the crucial need for effective identification and detection of H2S at the organellar level. Although numerous H2S fluorescent probes targeting organelles have been reported, a comprehensive review of these probes is required. This review focuses on the strategic selection of organelle-targeting groups and recognition sites for H2S fluorescent probes. This review examines H2S fluorescent probes that can specifically target lysosomes, mitochondria, endoplasmic reticulum, Golgi apparatus, and lipid droplets. These fluorescent probes have been meticulously classified and summarized based on their distinct targets, emphasizing their chemical structure, reaction mechanisms, and biological applications. We carefully designed fluorescent probes to efficiently enhance their ability to recognize target substances and exhibit significant fluorescence variations. Furthermore, we discuss the challenges inherent in the development of fluorescent probes and outline potential future directions for this exciting field.

Two-pronged strategy: A mitochondria targeting AIE photosensitizer for hydrogen sulfide detection and type I and type II photodynamic therapy

Multifunctional type-I photosensitizers (PSs) for hydrogen sulfide (H2S) detection and photodynamic therapy (PDT) of hypoxia tumors exhibits attractive curative effect but remains a challenging task. Herein, a mitochondria targeted aggregation-induced emission (AIE) photosensitizer TSPy-SS-P was designed and synthesized, which could be used for H2S detection and simultaneously type I and type II PDT. TSPy-SS-P had excellent selectivity and anti-interference abilities for endogenous and exogenous H2S detection in tumor cells. TSPy-SS-P was able to distinguish tumor cells with high level of H2S from normal cells by fluorescence "turn off" response to H2S. In addition, TSPy-SS-P showed type Ⅰ and type Ⅱ reactive oxygen species (ROS) generation ability to effectively ablate hypoxic tumor cells. TSPy-SS-P showed mitochondria targeting capacity which could produce ROS in situ to disrupt mitochondria and promote cell apoptosis. In vivo PDT experiments showcased that TSPy-SS-P had excellent tumor retention capability, effective tumor ablation ability and good biocompatibility. This work provided a two-pronged strategy to design organelles targeted photosensitizers for H2S detection and effective PDT of tumors.

Recent Research Progress of Benzothiazole Derivative Based Fluorescent Probes for Reactive Oxygen (H2O2 HClO) and Sulfide (H2S) Recognition

Fluorescent sensing technology has advantages such as high sensitivity, good selectivity, and easy operation. It is widely used in the environment and biomedical field and receives increasing attention from people. It is easy to modify the structure of the benzothiazole fluorophores, and adding the push-pull electronic system can regulate the optical properties of benzodiapylene molecules. As probes, its derivatives are widely used in biomedicine, catalysis, and materials. Therefore, this paper mainly describes the development in the detection of reactivated oxygen (H2O2 HClO) and sulfides (H2S) in the last six years (2019-2024) based on benzothiazole fluorescent probe, which will be classified according to the identification mechanism of probes to be summarized, and to explain their properties and applications in biological and food, providing some help for designing more sensitive and efficient fluorescent probe molecules.

Single Side-Chain-Modulatory of Hemicyanine for Optimized Fluorescence and Photoacoustic Dual-Modality Imaging of H2S In Vivo

Near-infrared fluorescence (NIRF)/photoacoustic (PA) dual-modality imaging integrated high-sensitivity fluorescence imaging with deep-penetration PA imaging has been recognized as a reliable tool for disease detection and diagnosis. However, it remains an immense challenge for a molecule probe to achieve the optimal NIRF and PA imaging by adjusting the energy allocation between radiative transition and nonradiative transition. Herein, a simple but effective strategy is reported to engineer a NIRF/PA dual-modality probe (Cl-HDN3) based on the near-infrared hemicyanine scaffold to optimize the energy allocation between radiative and nonradiative transition. Upon activation by H2S, the Cl-HDN3 shows a 3.6-fold enhancement in the PA signal and a 4.3-fold enhancement in the fluorescence signal. To achieve the sensitive and selective detection of H2S in vivo, the Cl-HDN3 is encapsulated within an amphiphilic lipid (DSPE-PEG2000) to form the Cl-HDN3-LP, which can successfully map the changes of H2S in a tumor-bearing mouse model with the NIRF/PA dual-modality imaging. This work presents a promising strategy for optimizing fluorescence and PA effects in a molecule probe, which may be extended to the NIRF/PA dual-modality imaging of other disease-relevant biomarkers.

Near-infrared Rhodols-based fluorescent probe with large Stokes shift for tracking of H2S in food spoilage and living cells

Hydrogen sulfide (H2S), as a biomarker signaling gas, is not only susceptible to food spoilage, but also plays a key function in many biological processes. In this work, an activated near infrared (NIR) H2S fluorescent probe was designed and synthesized with quinoline-conjugated Rhodols dye as fluorophore skeleton and a dinitrophenyl group as the responsive moiety. Due to the quenching effect of dinitrophenyl group and the closed-loop structure of Rhodols fluorophore, probe itself has a very weak absorption and fluorescence background signal. After the H2S-induced thiolysis reaction, the probe exhibits a remarkable colormetric change and NIR fluorescent enhancement response at 716 nm with large Stokes shift (116 nm), and possesses high sensing selectivity and sensitivity with a low detection limits of 330 nM. The response mechanism is systematically characterized by 1H NMR, MS and DFT calculations. The colorimetric change allows the probe to be used as a test strips to detect H2S in food spoilage, while NIR fluorescent response helps the probe monitor intracellular H2S.

Near-Infrared Fluorescent Probe for the Detection of Cysteine

Hemicyanine dyes are an ideal structure for building near-infrared fluorescent probes due to their excellent emission wavelength properties and biocompatibility in biological imaging field. Developing a near-infrared fluorescent probe capable of detecting cysteine (Cys) was the aim of this study. A novel developed fluorescent probe P showed high selectivity and sensitivity to Cys in the presence of various analytes. The detection limit of P was found to be 0.329 μM. The MTT assay showed that the probe was essentially non-cytotoxic. Furthermore, the probe was successfully used as cysteine imaging in living cells and mice.

A multifunctional fluorescent probe for sequential detection of hydrogen sulfide and pH in foodstuffs, living cells and mice

BACKGROUND

Cancer as a leading cause of premature death worldwide has become a major threat to human health due to the high incidence and mortality. Monitoring tumor markers are reliable and significantly important for early detection of cancers. In complex biological systems, it is of great urgency but still remains challenging to conceive a fluorescent probe with multiple tumor markers detection property. Hydrogen sulfide (H2S) and pH are two target biomarkers for diagnosis of early cancer. The preparation of a novel probe with H2S and pH dual detection functions is highly anticipated.

RESULTS

Herein, a novel sequential detection probe HTPQ-HS for H2S and pH has been developed. In this system, HPQ (2-(2 -hydroxyphenyl)-4(3H)-quinazolinone) structure combined with triphenylamine is applied as the fluorophore, and 2, 4-dinitrophenylsulfonyl group is used as the recognition group. In the presence of H2S, HTPQ-HS is transformed into product HTPQ-OH which shows fluorescence enhancement (29-fold) at 525 nm in less than 4 min and further displays repeatable acid-base responsive ability. HTPQ-HS is able to sequentially response to H2S and pH in living cells and does not react directly with pH. Owing to the low cytotoxicity, HTPQ-HS is able to detect exogenous and endogenous H2S in colon cancer cells and mice, monitor H2S in inflammation model and in foodstuffs. As the environment changes from acidic to alkaline, the fluorescence intensity ratio (I470/I530) of product HTPQ-OH changes remarkably, illustrating the ratiometric fluorescent responsiveness to pH.

SIGNIFICANCE AND NOVELTY

A multifunctional fluorescent probe HTPQ-HS for sequential detection of H2S and pH is synthesized. Probe HTPQ-OH realizes the monitoring of dynamic changes in intracellular pH and displays prospective application in security printing. We expect that our work could offer an important guidance on the development of multifunctional fluorescent probes for visualizing H2S and pH in biology and environment.

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 dicyanoisophorone-based long-wavelength fluorescent probe for detection of cysteine in vitro and in vivo

In this research, an "off-on" long-wavelength fluorescent probe (DCMN-Cl) based on (E)-2-(3-(2-(6-hydroxynaphthalen-2-yl)vinyl)-5,5-dimethylcyclohex-2-en-1-ylidene) malononitrile (DCMN) is designed and synthesized for cysteine (Cys) detection. DCMN-Cl exhibits a large Stokes shift (211 nm) and shows rapid response and high specificity to Cys. The fluorescence initensity at 635 nm reveals a good linear relationship with Cys concentration in the 0 to 50 μM range, and the detection limit is as low as 159 nM. The probe is also used for fluorescence imaging of Cys in cells and mice. Moreover, the probe provided visual evidence of Cu2+ and curcumin-induced intracellular Cys fluctuations.

Synthesis and applications of a corrole-based dual-responsive fluorescent probe for separate detection of hydrazine and hydrogen sulfide

Here, a corrole-based dual-responsive fluorescent probe DPC-DNBS was rationally designed and synthesized for the separate detection of hydrazine (N₂H₄) and hydrogen sulfide (H₂S) with high selectivity and sensitivity. The probe DPC-DNBS is intrinsically none fluorescent due to PET effect, however, addition of increasing amount of N₂H₄ or H₂S to DPC-DNBS turned on an excellent NIR fluorescence centered at 652 nm and thereby provided a colorimetric signaling behavior. The sensing mechanism was verified by HRMS, ¹H NMR and the DFT calculations. Common metal ions and anions do not interfere with the interactions of DPC-DNBS with N₂H₄ or H₂S. Furthermore, the presence of N₂H₄ does not affect the detection of H₂S; however, the presence of H₂S interferes with the detection of N₂H₄. Hence, quantitative detection of N₂H₄ must occur in an H₂S-free environment. The probe DPC-DNBS displayed some fascinating merits in separate detection of these two analytes, including large Stokes shift (233 nm), fast response (15 min for N₂H₄, 30 s for H₂S), low detection limit (90 nM for N₂H₄, 38 nM for H₂S), wide pH range (6-12) and outstanding biological compatibility. Significantly, DPC-DNBS was utilized to detect hydrazine in real water, soil and food samples. And its favorable performances for separate detection N₂H₄ and H₂S were successfully demonstrated in HeLa cells and zebrafish, indicating its value of practical application in biology.

A novel near-infrared fluorescent probe with large Stokes shift for imagining hydrogen sulfide

Hydrogen sulfide (H₂S) plays an important role in regulating varieties of important physiological and pathological processes. Thus the development of fluorescent probe for the detection of H₂S is of great significance and has attracted much attention recently. Herein, we reported a novel near-infrared (NIR) emitting fluorescent probe WFP-PC, which contained a positive charged hemicyanine-based WFP-OH as fluorophore and thiobenzoate unit as a specific reaction site. After treated with H₂S, the probe exhibited significant fluorescence enhancement and response time within 4 min and detection limit as low as 0.47 μM, accompanied by color changes from purple to blue. The probe was successfully applied to imaging the exogenous/endogenous H₂S in cells and mice, suggesting it could be a promising molecular tool for H₂S detection in living systems.

A selective fluorescent probe for hydrogen sulfide from a series of flavone derivatives and intracellular imaging

In this work, through the orthogonal design of two fluorophores and two recognition groups, a series of fluorescent probes were developed from the flavone derivatives for hydrogen sulfide (H₂S). The probe FlaN-DN stood out from the primarily screening on the selectivity and response intensities. It could respond to H₂S with both the chromogenic and fluorescent signals. Among the recent reported probes for the H₂S detection, FlaN-DN indicated the most highlighted advantages including the rapid response (within 200 s) and the high response multiplication (over 100 folds). FlaN-DN was sensitive to the pH condition, thus could be applied to distinguish the cancer micro-environment. Moreover, FlaN-DN suggested practical capabilities including a wide linear range (0-400 μM), a relatively high sensitivity (limit of detection 0.13 μM), and high selectivity towards H₂S. As a low cytotoxic probe, FlaN-DN achieved the imaging in living HeLa cells. FlaN-DN could detect the endogenous generation H₂S and visualize the dose-dependent responses to the exogenous H₂S level. This work provided a typical case of natural-sourced derivatives as functional implements, which might inspire the future investigations.

A turn-on fluorescent nanosensor for H2S detection and imaging in inflammatory cells and mice

Hydrogen sulfide (H₂S) is an endogenously generated gaseous signaling molecule and is known to be involved in the occurrence and development of inflammation. To better understand its physiological and pathological process of inflammation, reliable tools for H₂S detection in living inflammatory models are desired. Although a number of fluorescent sensors have been reported for H₂S detection and imaging, water-soluble and biocompatibility nanosensors are more useful for imaging in vivo. Herein, we developed a novel biological imaging nanosensor, XNP1, for inflammation-targeted imaging of H₂S. XNP1 was obtained by self-assembly of amphiphilic XNP1, which was constructed by the condensation reaction of the hydrophobic, H₂S response and deep red-emitting fluorophore with hydrophilic biopolymer glycol chitosan (GC). Without H₂S, XNP1 showed very low background fluorescence, while a significant enhancement in the fluorescence intensity of XNP1 was observed in the presence of H₂S, resulting in a high sensitivity toward H₂S in aqueous solution with a practical detection limit as low as 32.3 nM, which could be meet the detection of H₂S in vivo. XNP1 also has a good linear response concentration range (0-1 μM) toward H₂S with high selectivity over other competing species. These characteristics facilitate direct H₂S detection of the complex living inflammatory cells and drug-induced inflammatory mice, demonstrating its practical application in biosystems.