A novel water-soluble fluorescence probe based on ICT lighten for detecting hydrogen sulfide and its application in bioimaging

A highly sensitive and selective fluorescent "on-off-on" peptide-based probe for sequential detection of Hg2+ and S2- ions: Applications in living cells and zebrafish imaging

Mercury ions (Hg2+) and sulfur ions (S2-), have caused serious harm to the ecological environment and human health as two kinds of highly toxic pollutants widely used. Therefore, the visual quantitative determination of Hg2+ and S2- is of great significance in the field of environmental monitoring and medical therapy. In this study, a novel fluorescent "on-off-on" peptide-based probe DNC was designed and synthesized using dipeptide (Asn-Cys-NH2) as the raw material via solid phase peptide synthesis (SPPS) technology with Fmoc chemistry. DNC displayed high selectivity in the recognition of Hg2+, and formed non-fluorescence complex (DNC-Hg2+) through 2:1 binding mode. Notably, DNC-Hg2+ complex generated in situ was used as relay response probe for highly selective sequential detection of S2- through reversible formation-separation. DNC achieved highly sensitive detection of Hg2+ and S2- with the detection limits (LODs) of 8.4 nM and 5.5 nM, respectively. Meanwhile, DNC demonstrated feasibility for Hg2+ and S2- detections in two water samples, and the considerable recovery rate was obtained. More importantly, DNC showed excellent water solubility and low toxicity, and was successfully used for consecutive discerning Hg2+ and S2- in test strips, living cells and zebrafish larvae. As an effective visual analysis method in the field, smartphone RGB Color Picker APP realized semi-quantitative detections of Hg2+ and S2- without the need for complicated device.

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 ratiometric peptide-based fluorescent probe for sequential detection of Hg2+ and S2- ions and its application in living cells and zebrafish imaging

A new ratiometric peptide-based fluorescent probe DWPH was designed and synthesized, comprising dansyl fluorophore as a fluorescent dye, and tripeptide backbone (Trp-Pro-His-NH2) as a recognition group. The addition of Hg2+ caused the maximum emission peak of DWPH to blue shift from 560 nm to 510 nm. DWPH exhibited large Stokes shift (230 nm), satisfactory water solubility (100 % aqueous medium), good selectivity (only Hg2+), high sensitivity (24.6 nM), rapid response (within 50 s) and strong anti-interference ability for Hg2+ detection over a wide pH range (7-11). Additionally, the complex DWPH-Hg2+ as a relay response probe could also be applied to S2- according to displacement approach. Notably, the detection limit for S2- was calculated as 23.3 nM, exhibiting that DWPH showed great potential for environmental monitoring and bioimaging. In addition, DWPH were successfully used to determine Hg2+ and S2- in living cells and zebrafish based on excellent permeability and low cytotoxicity. What's more, the gradient concentration color changes of Hg2+ and S2- were combined with the smartphone APP to obtain red-green-blue (RGB) values, thus enabling rapid semi-quantitative detection of Hg2+ and S2- without expensive instruments.

Review of Chemical Sensors for Hydrogen Sulfide Detection in Organisms and Living Cells

As the third gasotransmitter, hydrogen sulfide (H₂S) is involved in a variety of physiological and pathological processes wherein abnormal levels of H₂S indicate various diseases. Therefore, an efficient and reliable monitoring of H₂S concentration in organisms and living cells is of great significance. Of diverse detection technologies, electrochemical sensors possess the unique advantages of miniaturization, fast detection, and high sensitivity, while the fluorescent and colorimetric ones exhibit exclusive visualization. All these chemical sensors are expected to be leveraged for H₂S detection in organisms and living cells, thus offering promising options for wearable devices. In this paper, the chemical sensors used to detect H₂S in the last 10 years are reviewed based on the different properties (metal affinity, reducibility, and nucleophilicity) of H₂S, simultaneously summarizing the detection materials, methods, linear range, detection limits, selectivity, etc. Meanwhile, the existing problems of such sensors and possible solutions are put forward. This review indicates that these types of chemical sensors competently serve as specific, accurate, highly selective, and sensitive sensor platforms for H₂S detection in organisms and living cells.

A novel peptide-based relay fluorescent probe with a large Stokes shift for detection of Hg2+ and S2- in 100 % aqueous medium and living cells: Visual detection via test strips and smartphone

Herein, a novel relay peptide-based fluorescent probe DGRK was synthesized via solid phase peptide synthesis (SPPS) technology. DGRK exhibited excellent water-solubility, good stability, remarkably large Stokes shift (230 nm) and high selectivity response to Hg²⁺ with a non-fluorescence complex DGRK-Hg²⁺ formation via a 1:1 binding mode. Further studies indicated that the DGRK-Hg²⁺ complex could act as a secondary probe for rapidly and sequentially detecting S^2- based on fluorescent "off-on" response, and without interference from a range of anions. The limit of detection (LOD) for Hg²⁺ and S^2- were calculated to be 33.6 nM and 60.9 nM, respectively. In addition, The reversibility of interaction of confirmed that the continuous and reversible recognition behavior of Hg²⁺ and S^2- by the probe DGRK, and could be cycled more than 5 times. In addition, DGRK could be successfully applied to the fluorescence imaging of Hg²⁺ and S^2- in two living cells based on excellent cells permeability and low cytotoxicity. Meanwhile, DGRK was successfully used to create the low-cost and portable test strips for visual detection and rapid analysis under 365 nm UV lamp, and the test strips combined with a smartphone (RGB color) was successfully applied to the semi-quantitative analysis and monitoring of dynamic changes of Hg²⁺ levels.

Design strategy for an analyte-compensated fluorescent probe to reduce its toxicity

During biological detection, the toxicity caused by probes to living organisms is neglected. In this study, an analyte-compensated fluorescent probe (NP-SN₃) was constructed for the detection of H₂S. Through experiments with HepG2 cells and zebrafish embryos and larvae, the NP-SN₃ probe showed no significant difference in imaging performance compared with the traditional probe (NP-N₃) but exhibited lower detection-induced toxicity in the imaging of liver fibrosis in activated HSC-T6 cells. During the development of zebrafish embryos and continuous administration in rats, NP-SN₃ showed a lower death rate, higher hatchability and lower malformation in zebrafish embryos and milder pathological symptoms in stained rat tissues.

Hydrogen sulfide detection and zebrafish imaging by a designed sensitive and selective fluorescent probe based on resorufin

A new long-wavelength fluorescent probe 1 that could specifically identify H₂S has been successfully synthesized and applied for imaging H₂S in zebrafish. Probe 1 was readily prepared by featuring nitrobenzene as the recognition unit coupled to resorufin. The fluorescence off-on response is based on the fact that H₂S can reduce the nitro group to an amino group, followed by the 1,6-rearrangement-elimination and the release of resorufin. By evaluating the application abilities of probe 1 in vivo and vitro, it is shown that probe 1 has high sensitivity and selectivity to H₂S, low background fluorescence interference, with a low detection limit of 17.30 μM. Notably, the occurrence of the reaction can be observed by the naked eye, and the color of the solution changes from yellow to pink. More importantly, it is the first time that using paper chips as carrier to detect H₂S, which lays a foundation for the practical application of detecting H₂S. The excellent analysis and application capabilities of probe 1 make it an effective tool for further application in practice.

An ESIPT-based colorimetric and fluorescent probe with large Stokes shift for the sensitive detection of hypochlorous acid and its bioimaging in cells

Hypochlorous acid (HOCl), with a low physiological concentration, plays a vital role in killing the pathogens and anti-inflammation in the human immune system.

ESIPT silent and mitochondrial-targeted rapid response for SO2 regulated by pyridinium and its real-time detection in living cells

ESIPT has been widely used in fluorescence recognition because of its advantages such as large Stokes shift.

A triphenylamine derived fluorescent probe for efficient detection of H2S based on aggregation-induced emission

The probe TPA-HS can quickly identify H₂S (20 minutes) and release TPA-CHO with aggregation-induced emission properties.

A simple fluorescent probe for detection of Ag+ and Cd2+ and its Cd2+ complex for sequential recognition of S2

In this study, we designed and synthesized a simple probe 2-(8-((8-methoxyquinolin-2-yl)methoxy)quinolin-2-yl)benzo[d]thiazole (DQT) for detection of Ag⁺ and Cd²⁺ in a CH₃OH/HEPES (9 : 1 v/v, pH = 7.30) buffer system. Its structure was characterized by NMR, ESI-HR-MS and DFT calculations, and its fluorescence performance was also investigated. Probe DQT showed fluorescence quenching in response to Ag⁺ and Cd²⁺ with low detection limits of 0.42 μM and 0.26 μM, respectively. Importantly, the complexation of the probe with Cd²⁺ resulted in a red shift from blue to green, making it possible to detect Ag⁺ and Cd²⁺ by the naked eye under an ultraviolet lamp. The DQT-Cd²⁺ complex could be used for sequential recognition of S^2-. The recovery response could be repeated 3 times by alternate addition of Cd²⁺ and S^2-. A filter paper strip test further demonstrated the potential of probe DQT as a convenient and rapid assay.

A rapid and sensitive fluorescent probe for detecting hydrogen polysulfides in living cells and zebra fish

Hydrogen polysulfides (H₂S_n, n>1) plays crucial roles in many biological processes, while it remains a challenge for rapid and selective detection of H₂S_n. We designed and synthesized a turn-on fluorescent probe (JCCF) for detecting H₂S_n based on a new julolidine-coumarinocoumarin scaffold. H₂S_n could trigger a dramatic fluorescence enhancement (52-fold) with a fast response time and a low detection limit of 98.3 nM (S/N = 3). Moreover, JCCF was successfully applied to image H₂S_n in living cells and zebra fish with low cytotoxicity.

A photostable fluorescent probe based on PET off for the detection of hydrogen sulfide and its application in bioimaging

As an important small gas signal molecule, H₂S has become an important research hotspot for both chemists and biologists.

A water soluble ratiometric fluorescent probe for targeting SO2 in mitochondria based on conjugated biquinolines

Despite the unprecedented development of SO₂ fluorescent probes in the past five years, the water-solubility of these probes is still an important factor related to their practical application.

A colorimetric and near-infrared fluorescent probe for detection of hydrogen sulfide and its real multiple applications

A novel colorimetric and near-infrared fluorescent probe (L) with D-π-A structure derived from 4-diethylaminosalicylaldehyde and 2-(3-cyano-4,5,5-trimethylfuran-2(5H)-ylidene)malononitrile has been developed. Probe L displays highly selective and sensitive recognition for H₂S over various anions with a large Stokes shift (96 nm) in DMF/H₂O (3/7, v/v, PBS-HCl 10 mM, pH = 7.4). A naked-eye observable color change of L solution from colorless to bluish-purple occurred on treatment with H₂S. The potential applications of probe L were evaluated and the results show that probe L can detect H₂S vapor and H₂S in real water, red wine and living cells.