Construction of a Novel Fluorescent Probe for On-site Measuring Hydrogen Sulfide Levels in Food Samples

A novel fluorescent probe with a phosphofluorene molecular structure for selective detection of hydrogen sulfide in living cells

Hydrogen sulfide (H2S) gas plays a significant role in biological regulation. With advancements in technology, H2S has been discovered across diverse fields, necessitating a comprehensive understanding of its physiological functions through monitoring changes in H2S within complex environments and physiological processes. In this study, we designed a phosphofluorene-based conjugate probe PPF-CDNB with an asymmetric π-conjugated phosphine structure and utilized dinitrophenyl ether as the recognition site for H2S. PPF-CDNB exhibited exceptional resistance to interference and demonstrated stability over a broad pH range (3.0-10.0), making it suitable for various environmental conditions. Intracellular experiments revealed that PPF-CDNB effectively monitored both endogenous and exogenous levels of H2S.

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.

Rational synthesis of 1,3,4-thiadiazole based ESIPT-fluorescent probe for detection of Cu2+ and H2S in herbs, wine and fruits

Here, 1,3,4-thiadiazole unit was employed as novel excited state intramolecular proton transfer (ESIPT) structure to prepare favorable fluorescent probe. High selectivity and rapid response to Cu2+ was obtained and the settling reaction was also used to recover ESIPT characteristics of probe to achieve sequential detection of H2S. Remarkable color change of solution from colorless to bright yellow and fluorescence emission from green to dark realized the visual detection of Cu2+ by naked eyes and transition of probe into portable fluorescent test strips. As expected, L-E could be utilized to quantitatively sense Cu2+ and H2S in different actual water and food samples including herbs, wine and fruits. The limits of detection for Cu2+ and H2S were as low as 34.5 nM and 38.6 nM. Also, probe L-E achieved real-time, portable, on-site quantitative detection of Cu2+ via a colorimeter and a smartphone platform with limit of detection to 90.3 nM.

All-in-one strategy for the nano-engineering of paper-based bifunctional fluorescent platform for robustly-integrated real-time monitoring of food and drinking-water safety

Cu2+ contamination and food spoilage raise food and drinking water safety issues, posing a serious threat to human health. Besides, Cu2+ and H2S levels indicate excess Cu2+-caused diseases and protein-containing food spoilage. Herein, a coumarin-containing bifunctional paper-based fluorescent platform integrated with a straightforward smartphone color recognition app is developed by an all-in-one strategy. The proposed fluorescent materials can simultaneously detect Cu2+ and H2S for on-demand food and drinking water safety monitoring at home. Specifically, a coumarin-derived fluorescence sensor (referred to as CMIA) with a low detection limit (0.430 μM) and high-selectivity/-sensitivity for Cu2+ is synthesized through a simple one-step route and then loaded onto commercially used cellulose fiber filter paper to engineer a biomass-based fluorescent material (CMIA-FP). The CMIA-FP offers user-friendly, high-precision, fast-responsive, and real-time visual monitoring of Cu2+. Moreover, CMIA forms a chemically stable complex with Cu2+, loaded onto filter paper to prepare another biomass-based fluorescent platform (CMIA-CU-FP) for visual real-time monitoring of H2S. Based on the exquisite composition design, the proposed dual-function paper-based fluorescent materials equipped with a smartphone color recognition program concurrently realize fast, accurate, and easy real-time monitoring of Cu2+ in drinking water and H2S in chicken breast-/shrimp-spoilage, demonstrating an effective detection strategy for the Cu2+ and H2S monitoring and presenting the new type of biomass-based platforms for concentrated reflection of drinking water and food safety.

Recent design strategies and applications of organic fluorescent probes for food freshness detection

Food spoilage poses a significant risk to human health, making the assessment of food freshness essential for ensuring food safety and quality. In recent years, there has been rapid progress in the development of fast detection technologies for food freshness. Among them, organic fluorescent probes have garnered significant attention in the field of food safety and sensing due to their easy functionalization, high sensitivity, and user-friendly nature. To comprehensively examine the latest advancements in organic fluorescent probes for food freshness detection, this review summarized their applications within the past five years. Initially, the fundamental detection principles of organic fluorescent probes are outlined. Subsequently, the recent research progress in utilizing organic fluorescent probes to detect various chemical indicators of freshness are discussed. Finally, the challenges and future directions for organic fluorescent probes in food freshness detection are elaborated upon. While, organic fluorescent probes have demonstrated their effectiveness in evaluating food freshness and possess great potential for practical applications, further research is still needed to enable their widespread commercial utilization. With continued advancements in synthesis and functionalization techniques, organic fluorescent probes will contribute to enhancing the efficiency of food safety detection.

A fluorous-tag-assisted fluorescent probe for simple and selective detection of hydrogen sulfide: application for turbid dyeing solutions

Accurate hydrogen sulfide (H2S) detection has attracted much attention because its toxicity may affect aquatic environments and human health. However, recognizing H2S levels by conventional fluorescent probes in turbid wastewater has been challenging because the opaque environment interferes with their photophysical properties. To overcome this limitation, a fluorous-tagging strategy can be used for the development of fluorescent sensors to detect H2S in turbid solutions. The use of fluorescent probe assisted with fluorous-tag allowed for easy isolation of the probe using polytetrafluoroethylene (PTFE) material, while disturbing species were eliminated through a simple aqueous wash. This approach enabled the fluorescent probe to effectively quantify H2S, even in opaque solutions containing organic dyes that could interfere with fluorescence emission.

Red-emitting fluorescent probe for hydrogen sulfide detection and its applications in food freshness determination and in vivo bioimaging

We report the development of a red-emitting fluorescence probe (XDS) for hydrogen sulfide (H₂S) detection in biosystems, real-world food samples, and application of this probe for monitoring of H₂S production during food spoilage. The XDS probe is developed by coupling of coumarin derivative to rhodanic-CN through a H₂S responsive CC bond. Remarkable fluorescence quenching of XDS is observed as a result of the response to H₂S. Semi-quantitative detection of H₂S in three real-world water and two beer samples and monitoring of H₂S production during food spoilage in real-time by "naked-eye" and smartphone colorimetric analysis are then achieved using XDS as the probe. Moreover, XDS is low toxicity, allowing it being used for visualizing endogenous and exogenous H₂S in vivo in a mouse model. It is expected that the successful development of XDS could provide an effective tool for investigating the roles of H₂S in biomedical system and for future food safety evaluation.

A novel chromophore reaction-based pyrrolopyrrole aza-BODIPY fluorescent probe for H2S detection and its application in food spoilage

In this work, we developed an aggregation-induced emission enhancement (AIEE) active and NIR emissive pyrrolopyrrole aza-BODIPY (PPAB) polymer (P1) for H₂S detection for the first time. P1 showed obvious colorimetric change from green to yellow-green and ratiometric fluorescence "turn on" phenomenon with 167 nm blue-shift (from dark red to bright green). The sensing mechanism revealed a novel chromophore reaction between imine in PPAB core and H₂S was involved, leading to less conjugated product. It exhibited distinct advantages of good selectivity, high sensitivity, and low detection limit of 0.66 μM. The potential applicability of P1 for H₂S detection in the real samples (tap water, lake water and milk) was demonstrated. In addition, the solid sensor prepared by loading P1 on the PMMA film was successfully realized the visual detection of gaseous H₂S gas produced from egg spoilage. Therefore, this work provides a promising approach based on novel sensing mechanism for monitoring H₂S in complicated biological systems and practical food samples.

Mitochondria-targeted fluorescent probe with long wavelength emission for detecting H2S and its application in foodstuff, water and living cells

Hydrogen sulfide (H₂S) is crucial to cellular energy production, apoptosis, and redox homeostasis in mitochondria of living cells. In this work, a unique mitochondria-targeting fluorescence probe (DDMI) was established for H₂S determination based on styrylpyridinium scaffold. When DDMI was treated with H₂S, it showed significant fluorescence enhancement at 623 nm, with good selectivity, and high sensitivity. In addition, the "turn-on" fluorescent probe DDMI could detect H₂S in water samples with good recoveries in the range of 95.4 %-105.6 % and track the degree of food spoilage by visualizing the change of DDMI-loaded test strips. Furthermore, the established probe DDMI was successfully used for monitoring exogenous H₂S in living cells and mitochondria targeting. These results paved the way for success in developing a technology that could be used to identify H₂S in environment, foodstuff, and living cells.

Growth studies of dominant lactic acid bacteria in orange juice and selection of strains to ferment citric fruit juices with probiotic potential

The study aimed to evaluate the ability of dominant lactic acid bacteria (LAB) in orange juice to growth on N-depleted MRS medium supplemented or not with cysteine (mMRS), then to select the most nutritionally promising strains for growth assays in the food matrix and evaluation of beneficial attributes for fruit juice fermentation. Levilactobacillus brevis and Lactiplantibacillus plantarum were dominant species among the total of 103 LAB isolates as confirmed by multiplex PCR and/or 16 s rDNA sequence analysis. Based on growing lower than 20% and higher than 70% in mMRS (1.0 g/l meat extract, without peptone and yeast extract) with and without cysteine requirement, one L. brevis (JNB23) and two L. plantarum (JNB21 and JNB25) were selected. These bacteria and the L. plantarum strains N4 and N8 (previously isolated from oranges peel) when inoculated in orange juice grew up to 1.0 log cfu/ml for 24 h incubation at 30 °C and mainly produced lactic acid, with strains JNB25 and JNB23 reaching the highest and lowest cell densities in agreement with their nutritional exigency. In addition, all L. plantarum strains exhibited antagonistic activity against the majority of tested bacterial pathogens (in opposition to L. brevis), ability to grow or survive to pH 3.0 for 3 h, to grow with 0.5% sodium taurocholate, and a decrease after simulated gastrointestinal digestion assay which did not exceed 1.0 or 2.0 log units, depending on the strain. Thus, autochthonous L. plantarum strains with ability for overcoming nutritional limitations and beneficial attributes are promising candidates for further investigations as novel probiotic and/or preservative starters to ferment citric fruit juices.

Reversible AIE-active fluorescent probe with a large emission peak shift for ratiometric detection of food freshness indicator H2S

It is crucial to on-site monitor H₂S for addressing the concerns associated with food safety. We rationally prepared an AIE-active fluorescent probe (CLBZ) with the aggregated state conversion for sensing H₂S in a ratiometric response manner. CLBZ displayed ratiometric response, fast response time (5 s), well-resolved emission peak shift (147 nm) and high selectivity towards H₂S, and it can be used as a reversible and reusable probe. The probe-based test strip was also developed to conveniently detect H₂S generated during food spoilage in the absence of laboratory instruments. It achieved the consistent results and sensitivity with that determined by the colony forming unit (CFU) assay. These results paved a successful way to develop an effective analytical method for food quality and safety.

A fluorimetric test strip with suppressed "Coffee Ring Effect" for selective mercury ion analysis

Nowadays, test strips are widely applied, but their use is mostly limited to the qualitative or half-quantitative analysis of targets. The main reason for their limited use is the "Coffee Ring Effect" (CRE) of probe materials, which leads to a heterogeneous probe distribution and poor testing reproducibility and sensitivity. In the present work, a fluorescent test strip was fabricated with a suppressed CRE of silver nanocluster (AgNC) probes coated by gelatin (Gel) under vacuum-aided fast lyophilization. Uniform and stable deposition of AgNC probes was achieved onto the test strips with a high loading capacity. The AgNCs displayed specific responses to Hg²⁺ ions, allowing sensitive and quantitative analysis in the linear concentration ranges from 0.20 to 50000 nM with a limit of detection of 0.10 nM. Given the advantages of rapid and facile preparation, CRE suppression, high biocompatibility, and cost-effectiveness, such a fabrication protocol may pave the way for the design of various test strips-based devices for point-of-care analytical applications in the fields of environmental monitoring, food quality analysis, and clinical diagnostics.

Highly Selective Electrochemiluminescence Chemosensor for Sulfide Enabled by Hierarchical Reactivity

Hydrogen sulfide (H₂S) is a well-known toxic gas with the odor of rotten eggs. Several reaction-based electrochemiluminescence (ECL) chemosensors for H₂S have been developed; however, no homogeneous ECL probe with high selectivity toward H₂S in aqueous media has been reported. Herein, we report an iridium(III) complex-based ECL chemodosimetric probe employing two 7-nitrobenz-2-oxa-1,3-diazol-4-yl (NBD) groups known as a photo-induced electron transfer quencher and a reaction site for the selective detection of H₂S; the detection mechanism involves H₂S being clearly distinguished from biothiols based on the different cleavage rates of the two NBD groups and extremely weak ECL interferences caused by reaction by-products. The probe was rationally designed to improve selectivity toward H₂S within the ECL analysis platform by enabling the removal of nonspecific background signals observed via fluorescence analysis. This analytical system exhibited remarkable selectivity toward H₂S, a rapid reaction rate, and high sensitivity (LOD = 57 nM) compared to conventional fluorescence methods. Furthermore, the probe could successfully quantify H₂S in tap water samples and commercial ammonium sulfide solutions, which demonstrates the effectiveness of this probe in field monitoring.

Two-photon ratiometric fluorescent probe based on NBD-amine functionalized semiconducting polymer nanoparticles for real-time imaging of hydrogen sulfide in living cells and zebrafish

The thiolysis of 7-nitro-1,2,3-benzoxadiazole amine (NBD-A) paves the way for specific sensing of H₂S over biothiols and real-time imaging in living organisms. Rational fabrication of NBD-A-based probe with ratiometric mode and two-photon excitation is highly appealing to achieve high quality bioimaging. In this work, the NBD-A molecules are assembled with poly(9,9-dioctylfluorenyl-2,7-diyl) polymer nanoparticles, defined as NBD@PFO, to construct two-photon ratiometric probes for H₂S detection through the fluorescence resonance energy transfer (FRET). For the construction of NBD@PFO nanohybrids, polymer nanoparticles are employed as the NBD-A molecular vehicle, energy donor and two-photon absorber, while NBD-A is served as the response unit and energy acceptor. Taking advantages of NBD-A and polymer nanoparticles, the obtained NBD@PFO probes exhibit high selectivity, fast response (<5 s), ratiometric detection and two-photon excitation. Our results indicate that NBD@PFO nanohybrids are successfully applied for monitoring of H₂S concentration in living cells and zebrafish, exhibiting great potential of polymer nanoparticles to improve the imaging capability of an organic small molecular probe.

Amphiphilic BODIPY-based nanoparticles as "light-up" fluorescent probe for PAEs detection by an aggregation/disaggregation approach

Phthalic acid eaters (PAEs) play the role of plasticizer and have been widely used in the industrial and plastic production process. But due to not chemically bound in the polymeric matrix, PAEs can be easily released directly and/or indirectly into the environment, and pose a threat the ecosystem and human health. Small-molecule self-assembled nanoparticles have drawn more and more attention due to advantages of precise molecular structure, biocompatibility, great diversity, and tunability in optical properties and functionalities. Here we report the use of disaggregation-induced emission (DIE) based supramolecular assembly to design organic nanoprobe for detection PAEs. In the water solution, the designed small organic fluorophore AJ-1 was aggregated via noncovalent forces to form fluorescence off nanoparticles, but in the presence of PAEs, they disaggregated and produced a clear light-up fluorescent signal. The detection of PAEs with selectivity, sensitivity and rapid response were further achieved. The experiment of recovery of PAEs in real-water sample illustrated the practicability of probe AJ-1 in real-world applications. Besides, cellular uptake assay suggested that AJ-1 could pass through membrane and gather in the cytoplasm.

Mitochondria-Targeted Red-Emission Fluorescent Probe for Ultrafast Detection of H2S in Food and Its Bioimaging Application

Hydrogen sulfide (H₂S) contributes to human health and prolongs the storage time of postharvest fruits and vegetables. At the same time, H₂S can cause a negative impact on some foodstuffs and beverages, so an efficient probe to detect H₂S is needed. Herein, a fluorescent turn-on responding probe SPy-DNs for H₂S detection has been designed and synthesized. SPy-DNs exhibited a red emission (608 nm), large Stokes shift (111 nm), and a detection limit of a nanomolar level (356 nM) in a dimethylformamide/phosphate-buffered saline (DMF/PBS) (1:1, v/v, 10 mM, pH 7.4) solution. SPy-DNs can detect H₂S with ultrafast response within 4 s, which is faster than the response of other reported probes. In addition, the applicability of SPy-DNs to detect H₂S has been determined in the actual water samples, targeted mitochondria, and imaged H₂S in living cells. Moreover, SPy-DNs was successfully used as a tool to judge H₂S levels in beer, which indicates that SPy-DNs possesses the advantage of rapid detection of H₂S in foodstuffs.

A novel fluorescent BODIPY-based probe for detection of Cu2+ and H2S based on displacement approach

A new BODIPY-based fluorescent probe (BC-DPA) was prepared by a simple method for Cu²⁺ detection in aqueous media and living cells. BC-DPA displayed excellent selectivity toward Cu²⁺via fluorescence "turn-off" mode when a mononuclear Cu(Ⅱ) complex is formed. The corresponding BC-DPA-Cu(Ⅱ) complex, whose structure was characterized by X-ray crystallography, has Cu(Ⅱ) in a distorted octahedral geometry. On the basis of the displacement approach, the fluorescence of BC-DPA-Cu²⁺ was recovered in the presence of S^2-, which allowed the system to act as a sensitive "turn-on" sensor for hydrogen sulfide. Furthermore, BC-DPA exhibited noticeable permeability and low cytotoxicity, making it a useful tool to detect Cu²⁺ in biosystems.

A multiple acetal chalcone-BODIPY-based fluorescence: synthesis, physical property, and biological studies

Fluorescent probes with outstanding physical and biological properties are superior for functional fluorescent dyes design. However, few studies pay attention to the stability of specific groups in fluorescent probes. The aldehyde group in the fluorescent probe is highly active but unstable under certain conditions. Therefore, we introduced ethoxy groups to realize the conversion to aldehyde groups under acidic conditions and avoid the instability of straightforward aldehyde groups. In this work, two fluorophores based on the multi acetal difluoroboraindacene (BODIPY) units with combination of the pharmaceutical intermediate chalcone have been firstly developed. In the design part, chalcone was introduced as a medium for fluorophore and multiple acetal. The mild synthesis strategy is based on the ligand ((Z)-2-chloro-1-(difluoroboranyl)-5-((4-ethyl-3,5-dimethyl-2H-pyrrol-2-ylidene)(phenyl)methyl)-1H-pyrrole) and connects with chalcone in (2E,2'E)-3,3'-(1,3-phenylene)bis(1-(2,4-bis(2,2-diethoxyethoxy)phenyl)prop-2-en-1-one). The emission wavelengths of the products are around 530 nm with high fluorescence intensity. To highlight the biological characteristics of these novel BODIPY fluorescents, we further demonstrated biological analysis studies on MTT and flow cytometry assays. The IC₅₀ values of BODIPY 5 ranged from 79 ± 6.11 to 63 ± 5.67 μM and BODIPY 6 were found to be 86 ± 4.07 to 58 ± 10.51 μM in tested cell lines. Flow cytometry data analysis shows that the representative agent 6 and reference have similar rational apoptosis rates in first quadrant. Last but not least, 6 shows outstanding biological compatibility and cell imaging potential in live cell imaging and in vivo assay, not only is the fluorescence prominent enough, but also rapidly distributes. Thus, our study reports a mild synthesis strategy and full biological analysis on BODIPY fluorescents, and the subtle modulation of the physical and biological properties by pharmaceutical substituents makes these designed chalcone-BODIPY-based dyes hopeful to realize drug functional fluorescent dyes. Two new highly sensitive BODIPY fluorophores are synthesized based on the ligand ((Z)-2-chloro-1-(difluoroboranyl)-5-((4-ethyl-3,5-dimethyl-2H-pyrrol-2-ylidene)(phenyl)methyl)-1H-pyrrole), which connects with chalcone in (2E,2'E)-3,3'-(1,3/4-phenylene)bis(1-(2,4-bis(2,2-diethoxyethoxy)phenyl)prop-2-en-1-one). Multiple acetals were introduced and the physical and biological properties of BODIPYs are described with MTT assay and in vitro and in vivo imaging.

Sensing of Hydrogen Sulfide Gas in the Raman-Silent Region Based on Gold Nano-Bipyramids (Au NBPs) Encapsulated by Zeolitic Imidazolate Framework-8

Mostly, surface-enhanced Raman scattering (SERS) sensors used the Raman characteristic bands concentrated in the Raman "fingerprint" region (500-1800 cm^-1), which may result in spectral overlapping interference. The study of the response in the Raman-silent region (10-500 and 1800-2800 cm^-1) can help overcome this problem. Hydrogen sulfide (H₂S) gas causes a great threat to human's health, but its low concentration in the airborne species is a challenge for sensitive and selective detection. Herein, a novel low-wavenumber (10-500 cm^-1) SERS sensor for H₂S gas detection has been developed based on gold nano-bipyramids (Au NBPs) encapsulated by zeolitic imidazolate framework-8 (ZIF-8) (Au NBPs@ZIF-8). The sensor takes advantage of the high adsorption capacity of ZIF-8 toward H₂S gas and the H₂S-triggered SERS spectral changes in the low-wavenumber Raman-silent region. A clear SERS peak of Au-Br at ∼175 cm^-1 generated from Au NBPs@ZIF-8 showed a decrease in the presence of H₂S because of the competition of adsorption sites between Au-S and Au-Br bonds. Furthermore, Au NBPs@ZIF-8 can enrich and monitor the level of H₂S gas with high efficiency and low interference. The developed sensor has a detection range of 0.2 nM to 20 mM with a limit of detection (LOD) of 0.17 nM. The developed sensor had been applied to detect the H₂S gas released from the spoiled fish meat with high selectivity.

Microenvironment-Sensitive Fluorescent Ligand Binds Ascaris Telomere Antiparallel G-Quadruplex DNA with Blue-Shift and Enhanced Emission

The development of small molecules that can selectively target G-quadruplex (G4) DNAs has drawn considerable attention due to their unique physiological and pathological functions. However, only a few molecules have been found to selectively bind a particular G4 DNA structure. We have developed a fluorescence ligand Q1, a molecular scaffold with a carbazole-pyridine core bridged by a phenylboronic acid side chain, that acts as a selective ascaris telomere antiparallel G4 DNA ASC20 ligand with about 18 nm blue-shifted and enhanced fluorescence intensity. Photophysical properties revealed that Q1 was sensitive to the microenvironment and gave the best selectivity to ASC20 with an equilibrium binding constant K_a =6.04×10⁵  M^-1 . Time-resolved fluorescence studies also demonstrated that Q1 showed a longer fluorescence lifetime in the presence of ASC20. The binding characteristics of Q1 with ASC20 were shown in detail in a fluorescent intercalator displacement (FID) assay, a 2-Ap titration experiment and by molecular docking. Ligand Q1 could adopt an appropriate pose at terminal G-quartets of ASC20 through multiple interactions including π-π stacking between aromatic rings; this led to strong fluorescence enhancement. In addition, a co-staining image showed that Q1 is mainly distributed in the cytoplasm. Accordingly, this work provides insights for the development of ligands that selectively targeting a specific G4 DNA structure.

A Simple Water-Soluble ESIPT Fluorescent Probe for Fluoride Ion with Large Stokes Shift in Living Cells

Developing an effective method for monitoring fluoride ion in biological samples is meaningful because fluoride ion plays a vital role in biological processes. In this contribution, a simple water-soluble ESIPT fluorescent probe 2-((4-((tert-butyldiphenylsilyl)oxy)-1,3-dioxoisoindolin-2-yl)methyl)-1-ethylpyridin-1-ium iodide (SPI) was constructed for monitoring fluoride ion. The probe SPI containing pyridinium salt group exhibited preeminent water solubility. The probe SPI introducing a trimethyldiphenylsilyl ether recognition group displayed excellent selectivity for fluoride ion over other biologically relevant species. Additionally, the probe SPI exhibited a fast response for a fluoride ion, suggesting that it could provide real-time fluoride ion detection. Importantly, the probe could detect fluoride ion with a linear range of 0-70.0 × 10-6 M and a low detection limit of 1.16 × 10-6 M. Furthermore, probe SPI could detect fluoride ion with a large Stokes shift (98 nm), which was attributed to ESIPT fluorescence sensing process. At last, probe SPI was successfully employed to monitor fluoride ion in living cells.

Conjugating a groove binder analogue to a styryl-quinolinium scaffold for the light-up detection of duplex and G-Quadruplex DNA with different binding modes

The rational design of novel small molecules, which can target specific DNA sequences or secondary structural DNAs, is one of the most important goals in medicinal chemistry. Also the studies of DNA binding potency which can give fundamental insight into binding mechanisms and specificity are essential. In this paper, a N-methylated quinolinium probe NSQ functionalized with a G-Quadruplex DNA groove binder analogue was designed and synthesized. NSQ was found to express selective and sensitive for "light-up" detection of both G-Quadruplex and duplex DNAs over RNA and other biomolecules. The characteristics of NSQ and its interactions with DNAs were comprehensively evaluated by means of fluorescence, UV-Vis, circular dichroism, FID assay, DFT calculation and molecular docking. NSQ exhibited higher binding affinity to G-Quadruplex than to duplex DNA. Binding mechanism analysis indicated NSQ interacted with G-Quadruplex DNA mainly through end-stacking mode, while bound with duplex DNA into the minor groove of AT-rich regions. Further, NSQ exhibited potent in vitro anti-tumor activity, and to elucidate the cellular applications, confocal cell imaging was carried out and validated its mainly nuclear localization.

An amphiphilic BODIPY-based selective probe for parallel G4 DNA targeting via disaggregation-induced emission

An amphiphilic BODIPY-based probe, AB-1, was established for parallel G4 DNA targeting based on the concept of triggered disaggregation-induced emission.

Tetranitrile-anthracene as a probe for fluorescence detection of viscosity in fluid drinks via aggregation-induced emission

An AIE-based fluorescent probe was developed for monitoring the viscosity change during the spoilage process of fluid drinks.