A rapid and specific fluorescent probe based on aggregation-induced emission enhancement for mercury ion detection in living systems

Design and Synthesis of two novel carbazole-based fluorescent probes and their application in detecting Hg2

Mercury is a highly toxic and non-degradable heavy metal pollutant that poses great harm to human health and the ecological environment. Two novel carbazole based thioacetal fluorescent probes 4a and 4b for highly sensitive and selective detection of Hg2+ have been designed and synthesized. Though both probes 4a and 4b can detect Hg2+ through thioacetal deprotection reaction, due to the difference in structural stability and the AIE effect of probe 4a, probe 4a has higher selectivity and sensitivity, with a detection limit as low as 5.1 × 10-8 M and a response time of approximately 25 s. In addition, probe 4a can detect Hg2+ under the solvent systems with high water content, thus we have successfully applied probe 4a to the detection of Hg2+ in actual water and soil samples, and used it as test strips.

Highly selective peptide-based fluorescent probe with aggregation induced emission (AIE) for detection of chondroitin sulfate and its application in living cells and zebrafish imaging

Chondroitin sulfate (CS), as a kind of acid mucosaccharide with natural activity, has shown various physiological activities in human body due to its advantages of high biocompatibility, good degradability and little side effects. Herein, a novel and simple peptide probe (TPE-ASRH) based on tetraphenylethene (TPE) and tetrapeptide (Ala-Ser-Arg-His-NH2) was designed and synthesized. TPE-ASRH displayed remarkable aggregation induced emission (AIE) characteristic in DMSO/water binary mixture. Based on electrostatic attraction, TPE-ASRH displayed highly selective and sensitive detection to chondroitin sulfate with large Stokes shift (156 nm), and the limit of detection (LOD) for chondroitin sulfate was calculated to be 0.11 nM based on 3σ/k. In addition, the colour change of TPE-ASRH was observed significantly from midnightblue to steelblue after adding chondroitin sulfate using naked eyes under 365 nm UV irradiation. Meanwhile, TPE-ASRH was able to achieve a rapid response to chondroitin sulfate (less than 30 s) with a pH response range of 3-12, which indicated that TPE-ASRH can detect chondroitin sulfate rapidly under physiological conditions. The response mechanism of TPE-ASRH to chondroitin sulfate was demonstrated using Zeta particle size and potential, UV-vis titration spectroscopy, FTIR spectra and CD spectroscopy. Most importantly, TPE-ASRH revealed the considerably low cytotoxic effects and good biological permeability, and was successfully applied to image chondroitin sulfate in living cells and zebrafish.

A novel dual-function peptide-based fluorescent probe with large Stokes shift for the simultaneous detection and quantification of Ag(I) and Hg(II) ions

Achieving highly selective detections of Ag+ and Hg2+ is of great importance because their excessive emission can cause many diseases. Herein, a novel large Stokes shift fluorescent probe DKT based on dansyl fluorophore modified peptide biomolecules (NH2-Thr-Lys-Thr-NH2) was successfully synthesized, which can simultaneously detect Ag+ (turn on) and Hg2+ (turn off) based on different fluorescent response patterns in 100% aqueous solution. DKT also enables quantitative detection of Ag+ and Hg2+ with LODs of 37.1 nM and 26.7 nM, respectively. Besides, ESI-HRMS spectra, Job's plot, and fluorometric titration confirmed that the binding stoichiometry was determined to be 2: 1 between DKT and Ag+/Hg2+. Moreover, DKT has good fluorescence stability and rapidly detected Ag+ and Hg2+ over a wide pH range. Furthermore, DKT was applied to quantitative detect Ag+ and Hg2+ in three actual water samples, three tea samples and watermelon juice, which exhibited that DKT has good potential for accuracy in environmental monitoring and water quality control. Additionally, the results of fluorescence bioimaging showed that DKT had significant distinguishing ability to detect Ag+ and Hg2+ in living cells and zebrafish larvae. More importantly, smartphone App platform based on DKT not only provided a reliable new method for the field quantitative monitoring of Ag+ and Hg2+, but also expanded its application prospect in the field of heavy metal ions pollution detection.

A large Stokes shift peptide-based fluorescent probe for Cd2+ and Hg2+ detection in aqueous solution and its applications in bioimaging, real sample, logic gate and smartphone device

Realize the efficient and sensitive detection of cadmium ions (Cd2+) and mercury ions (Hg2+) based on different response modes is of great significance because their large emissions seriously harm the ecological environment and human health. Herein, a novel peptide-based fluorescent probe named DGGC was synthesized and characterized with satisfactory water solubility (100 % aqueous solution) and significantly large Stokes (230 nm). DGGC exhibited high selectivity and excellent sensitivity towards Cd2+ based on fluorescence enhancement response and Hg2+ based on fluorescence quenching response. The limit of detections (LODs) for Cd2+ and Hg2+ were as low as 8.6 nM and 35.1 nM, respectively. The results of fluorescence titration, Job's plot analysis and ESI-HRMS data revealed that DGGC combined with Cd2+ and Hg2+ in a 2:1 stoichiometric ratio. Additionally, the bioimaging results demonstrated that significant discrimination sensitivity of DGGC for imaging of Cd2+ and Hg2+ in living cells and zebrafish larvae. In addition, DGGC showed high precision and accuracy in the quantitative analysis of Cd2+ and Hg2+ in various real samples. Furthermore, DGGC monitored Cd2+ and Hg2+ contamination on the surface of rice, leaves, kiwifruit and pumpkin under 365 nm UV light using naked eyes. The fluorescence change of DGGC after the addition of Cd2+ and Hg2+ was used as an INHIBIT logic gate. More significantly, the smartphone colour recognition App was successfully applied to the semi-quantitative detection  of Cd2+ and Hg2+ without the need for a large instrument.

A reversible aggregation-induced emission fluorescent probe for dynamic visualization of intracellular mercury(II) and cell state differentiation

The dynamic interplay between toxic mercury ions (Hg2 +) and reactive sulfur species (RSS) in living systems plays a crucial role in cellular defense mechanisms and redox homeostasis. However, current fluorescent probes for Hg2+ are limited by their irreversibility and inability to provide the real-time information. Herein, we present a novel reversible aggregation-induced emission (AIE) fluorescent probe, NI-PSO, that overcomes these limitations. NI-PSO exhibits a remarkable 160-fold fluorescence enhancement upon Hg2+ binding with high sensitivity and selectivity. The probe's unique reversibility, facilitated by the coordination interaction between phenylthioether and Hg2+, enables real-time monitoring of mitochondrial Hg2+ in the presence of exogenous and endogenous RSS. Notably, by visualizing Hg2+ dynamics, NI-PSO successfully differentiates various cellular states, including normal, inflammatory, and cancerous cells, providing insights into the role of RSS in mercury detoxification and maintaining cellular redox homeostasis. Our design opens up new avenues for investigating dynamic biological processes and their implications in health and disease.

A Rhodamine-based high-sensitivity low-cytotoxicity probe for rapid turn-on detection of Hg2

By integrating Rhodamine B and 4-phenylmorpholine moieties, a novel fluorescent probe named RhPy is synthesized for detecting Hg2+. Its recognition mechanism involves the reaction of Hg2+ with dithiooxamide, ultimately triggering the opening of the Rhodamine spirolactam and forming a new molecule RhPy-S with strong emission. The probe exhibits impressive limit of detection (0.015 μM) and short response time (<10 s). Importantly, RhPy shows almost none-cytotoxicity and RhPy-S has the emission spectrum peaking at 596 nm, which endow the probe with a good tissue penetration ability and practical utility in living cells, zebrafish and in vivo mice models. This work advances the field by providing a highly sensitive chemosensor for both environmental and biological applications.

Fluorometric Innovations for Ultrasensitive Trace Element Analysis in Environmental Matrices

Trace elements in environmental matrices and their potential harm to humans and the ecosystem are causing growing concern. For environmental monitoring and assessment, trace element analysis in water, soil, and air must be precise. Due to its selectivity and sensitivity, fluorometric analysis has grown in popularity. This review covers the latest fluorometric approaches for trace element measurement in environmental samples. This review discusses sensitive and selective fluorometric probes. A significant increase in fluorescence intensity makes this probe better for trace element research. Various parameters like pH, temperature, and reaction time were carefully optimized in each approach to increase sensitivity and accuracy. The current study sheds light on this analytical approach's concepts, applications, and difficulties. In general, fluorometric analysis is important for environmental studies. For researchers, it allows them to use fluorometric technology with other methods and focus on real-time analysis to solve environmental challenges.

Heteroaryl-Fused Triazapentalenes: Synthesis and Aggregation-Induced Emission

A pyridine-fused triazapentalene shows weak fluorescence in solution and is readily accessible via nitrene-mediated cyclization. In this study, a modified Cadogan reaction was used to synthesize HetATAP 1. Palladium-catalyzed reactions have been used as post-functionalization methods. Interestingly, modified Suzuki cross-couplings with various boronic acids resulted in poor to moderate yields of HetATAPs 2-5 which were arylated at the azole moiety. Direct CH arylation of HetATAP 1 gave the products with the same regiochemistry in satisfactory yields. The structures of HetATAPs 2-5 were confirmed using NMR analysis. In addition, the photophysical properties of HetATAPs 1-5 were studied under various conditions. Particularly, the emission of HetATAPs 2-5 is enhanced in the solid and aggregate state.

Detection of Hg2+ Using a Dual-Mode Biosensing Probe Constructed Using Ratiometric Fluorescent Copper Nanoclusters@Zirconia Metal-Organic Framework/N-Methyl Mesoporphyrin IX and Colorimetry G-Quadruplex/Hemin Peroxidase-Mimicking G-Quadruplex DNAzyme

Mercury (Hg2+) has been recognized as a global pollutant with a toxic, mobile, and persistent nature. It adversely affects the ecosystem and human health. Already developed biosensors for Hg2+ detection majorly suffer from poor sensitivity and specificity. Herein, a colorimetric/fluorimetric dual-mode sensing approach is designed for the quantitative detection of Hg2+. This novel sensing approach utilizes nanofluorophores, i.e., fluorescent copper nanoclusters-doped zirconia metal-organic framework (CuNCs@Zr-MOF) nanoconjugate (blue color) and N-methyl mesoporphyrin IX (NMM) (red color) in combination with peroxidase-mimicking G-quadruplex DNAzyme (PMDNAzyme). In the presence of Hg2+, dabcyl conjugated complementary DNA with T-T mismatches form the stable duplex with the CuNCs@Zr-MOF@G-quadruplex structure through T-Hg2+-T base pairing. It causes the quenching of fluorescence of CuNCs@Zr-MOF (463 nm) due to the Förster resonance energy transfer (FRET) system. Moreover, the G-quadruplex (G4) structure of the aptamer enhances the fluorescence emission of NMM (610 nm). Besides this, the peroxidase-like activity of G4/hemin DNAzyme offers the colorimetric detection of Hg2+. The formation of duplex with PMDNAzyme increases the catalytic activity. This novel biosensing probe quantitatively detected Hg2+ using both fluorimetry and colorimetry approaches with a low detection limit of 0.59 and 36.3 nM, respectively. It was also observed that the presence of interfering metal ions in case of real aqueous samples does not affect the performance of this novel biosensing probe. These findings confirm the considerable potential of the proposed biosensing probe to screen the concentration of Hg2+ in aquatic products.

A MELET- and IFE-based UV-visible luminescent ratiometric probe for quantization of mercury(II) and nitrofurantoin in environmental sewage

A novel fluorimetric ratiometric probe of green and eco-friendily nitrogen-enriched, oxygen-doped carbon nanodots (Cnanodots) was prepared for the quantitative analysis of mercury(II) (HgII) and nitrofurantoin (Nit) in the environmental sewage. The Cnanodots exhibits dual-emission peaks respectively at 345 and 445 nm under 285 nm excitation, with excitation-independent properties. Unexpectedly, this Cnanodots displays two obvious ratiometric responses to HgII and Nit through decreasing the signal at 345 nm and remaining invariable at 445 nm. Experimental results confirm that the highly sensitive analysis of HgII and Nit are achieved respectively based on matching energy-level electron transfer and inner filter effect mechanisms. The fluorescence (FL) ratiometric intensity of [FL345nm/FL445nm] expresses a good linear relationship with the concentration of HgII in the scope of 0.01-20 μM, while the logarithm of [Log(FL0345nm-FL345nm)] on the quenching degree of the probe by Nit also shows a good linear correlation within the range of 0.01-100 μM. The detection limits were calculated to be 4.14 nM for HgII, and 7.84 nM for Nit. Moreover, recovery experiments of Cnanodots for HgII and Nit sensing in real sewage samples obtained satisfactory results, comfirming the feasibility of practical application.

A turn-on anthraquinone-derived colorimetric and fluorometric dual-mode probe for highly selective Hg2+ determination and bioimaging in living organisms

Mercury ion (Hg2+) is considered a harmful neurotoxin, and real-time monitoring of Hg2+ concentrations in environmental and biological samples is critical. Fluorescent probes are a rapidly emerging visualization tool owing to their simple design and good selectivity. Herein, a novel fluorescence (FL) probe 2-(4-((6-((quinolin-8-yloxy)methyl)pyridin-2-yl)methyl)piperazin-1-yl)anthracene-9,10-dione (QPPA) is designed using piperazine as a linker between the anthraquinone group, which serves as a fluorophore, and N4O as the Hg2+ ligand. The probe exhibits FL "turn-on" sensing of Hg2+ because the complex inhibits the photo-induced electron transfer (PET) process. Moreover, QPPA can overcome the invasion by other possible cations, resulting in a clear color change from orange to colorless with the addition Hg2+. The chelation of QPPA with Hg2+ in a 1:1 ratio. Subsequently, the theoretically determined binding sites of the ligand to Hg2+ are validated through 1H NMR titration. The in situQPPA-Hg2+ complex can be subjected to Hg2+ extraction following the introduction of S2- owing to its robust binding capacity. The exceptional limit of detection values for Hg2+ and S2- are obtained as 63.0 and 79.1 nM (S/N = 3), respectively. Moreover, QPPA can display bright red FL in the presence of Hg2+ in different biological specimens such as HeLa cells, zebrafish, onion root tip tissues, and water flea Daphnia carinata, further providing an effective strategy for environmental monitoring and bioimaging of Hg2+ in living organisms.

Nitrogen and Sulfur Co-doped Carbon Dots for Ratiometric Fluorometric Determination of Mercury Ions

Nitrogen and sulfur co-doped carbon dots (N, S-CDs) were prepared for dual-channel ratiometric fluorescence determination of mercury ions (Hg2+). The dual-emission N, S-CDs were synthesized using a simple one-pot hydrothermal treatment. When excited with visible light, N,S-CDs exhibited two emission peaks at 390 and 500 nm. Notably, the presence of Hg2+ caused a considerable decrease in the fluorescence of N, S-CDs at 500 nm, mainly due to the static quenching effect. In comparison, the fluorescence at 390 nm was almost unchanged. With a limit of detection (LOD) of 0.21 µM for Hg2+, the N, S-CDs were successfully applied to the unlabeled ratiometric fluorescence determination of Hg2+ in actual water samples with good recoveries (94.5-107.8%). In conclusion, this developed ratiometric fluorescent sensor provides a reliable, environmentally friendly, rapid, and efficient platform for detecting Hg2+ in environmental applications.

Real time monitoring of nerve agent mimics: Novel solid state emitter for enhanced precision and reliability

Chemical nerve agents are hazardous compounds that terrorists can exploit to pose a significant threat to public safety and national security. The nucleophilic behaviour of these agents enables their interaction with acetyl cholinesterase in the body, leading to paralysis and potentially fatal consequences. Therefore, developing robust and efficient detection methods for these agents is crucial for preventing their misuse. In this manuscript, (E)-12-(1-hydrazineylideneethyl)benzo[f]pyrido[1,2-a]indole-6,11-dione (HBID) is developed as a novel colorimetric and fluorometric probe for the detection of specific chemical nerve agent simulants in both liquid and vapor phase. HBID reacts rapidly with diethyl chlorophosphate (DCP), a common nerve agent simulant, leading to a significant increase in the fluorescence intensity. Under optimized conditions, HBID exhibits high sensitivity, good recyclability, fast response and low limit of detection (0.092 µM). NMR and mass spectral studies suggest that the reaction involves the nucleophilic addition of HBID to DCP, forming a phosphate ester. Additionally, the developed sensor demonstrates viscosity-sensitive AIE phenomena thus greatly expanding its potential applications in biological systems. This sensitivity enables precise detection and visualization of viscosity changes within cellular environments, making the sensor an invaluable tool for studying complex biological processes. The developed probe also detects pH within biologically relevant range (4-6). In practical applications, the probe-treated strips efficiently detected DCP vapor in real time, showing a noticeable fluorescence response. Further, the probe has a strong potential to detect the presence of DCP in the soil samples.

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.

A dual-signals fluorometric and colorimetric peptide-based probe for Cu(II) and glyphosate detection and its application for bioimaging and water testing

A novel dual-signal fluorometric and colorimetric probe FMDH (5-FAM-Met-Asp-His-NH2), incorporating a tripeptide (Met-Asp-His-NH2) linked to 5-carboxyfluorescein (5-FAM), was firstly synthesised. FMDH demonstrated exceptional selectivity and sensitivity, rapid response, wide pH response range and robust anti-interference capabilities for monitoring Cu2+. This was achieved through a distinctive naked-eye colorimetric and fluorescent quenching behaviour. A good linearity within the range of 0-3 μM (R2 = 0.9914) was attained, and the limit of detection (LOD) for Cu2+ was 47.4 nM. Furthermore, the FMDH-Cu2+ ensemble responded to glyphosate with notable selectivity and sensitivity. A good linear correlation (R2 = 0.9926) was observed at the lower concentration range (2.4-7.8 μM) and achieving a detection limit as low as 29.9 nM. The response time of FMDH with Cu2+ and glyphosate were less than 20 s, and the pH range of 7-11 that was suitable for practical application under physiological pH conditions. MTT assays confirmed that FMDH offers good permeability and low toxicity, facilitating successful application in imaging analysis of Cu2+ and glyphosate in living cells and zebrafish. In addition, FMDH was employed in the detection of these analytes in real water samples. Cost-effective, highly sensitive and easily prepared FMDH-impregnated test strips were developed for the efficient visual detection of Cu2+ and glyphosate under 365 nm UV light. Increasing concentrations of Cu2+ and glyphosate resulted in notable colour changes under 365 nm UV light, enabling visual semi-quantitative analysis via a smartphone colour-analysis App.

Rational design of peptide-based fluorescent probe for sequential recognitions of Cu(II) ions and glyphosate: Smartphone, test strip, real sample and living cells applications

A new peptide-based fluorescent probe named DMDH with easy-to-synthesize, excellent stability, good water solubility and large Stokes shift (225 nm) was synthesized for highly selective sequential detections of copper ions (Cu2+) and glyphosate (Glyp). DMDH demonstrated great detection performance towards Cu2+via strong fluorescence quenching, and forming non-fluorescence DMDH-Cu2+ ensemble. As a new promising cascade probe, the fluorescence of DMDH-Cu2+ ensemble was significantly recovered based on displacement approach after glyphosate was added. Interestingly, the limit of detections (LODs) for Cu2+ and glyphosate were 40.6 nM and 10.6 nM, respectively, which were far lower than those recommended by the WHO guidelines for drinking water. More importantly, DMDH was utilized to evaluate Cu2+ and glyphosate content in three real water samples, demonstrating that its effectiveness in water quality monitoring. Additionally, it is worth noting that DMDH was also applied to analyze Cu2+ and glyphosate in living cells in view of significant cells permeability and low cytotoxicity. Moreover, DMDH soaked in filter paper was used to create qualitative test strips and visually identify Cu2+ and glyphosate through significant color changes. Furthermore, smartphone RGB color recognition provided a new method for semi-quantitative testing of Cu2+ and glyphosate in the absence of expensive instruments.

Label-free multi-line immunochromatographic sensor based on TCBPE for broad-spectrum detection Salmonella in food

BACKGROUND

Salmonella, a foodborne pathogen poses significant threats to food safety and human health. Immunochromatographic (ICTS) sensors have gained popularity in the field of food safety due to their convenience, speed, and cost-effectiveness. However, most existing ICTS sensors rely on antibody sandwich structures which are limited by their dependence on high-quality paired antibodies and restricted sensitivity. For the first time, we combined multi-line ICTS strips with fluorescent bacterial probes to develop a label-free multi-line immunochromatographic sensor capable of detecting broad-spectrum Salmonella. Salmonella was labeled with the aggregation-induced luminescence material TCBPE, resulting in its transformation into a green fluorescent probe.

RESULTS

Using this sensor, we successfully detected Salmonella typhimurium within the concentration range of 104-108 CFU/mL with a visual detection limit of 6.0 × 104 CFU/mL. Compared to single-line sensors, our multi-line sensor exhibited significantly improved fluorescence intensity resulting in enhanced detection sensitivity by 50 %. Furthermore, our developed multi-line ICTS sensor demonstrated successful detection of 18 different strains of Salmonella without any cross-reaction observed with 5 common foodborne pathogens tested. The applicability and reliability were validated using milk samples, cabbage juice samples as well and drinking water samples suggesting its potential for rapid and accurate detection of Salmonella in real-world scenarios across both the food industry and clinical settings.

SIGNIFICANCE

In this experiment, we developed a TCBPE-based multiline immunochromatographic sensor. Specifically, Salmonella was labeled with the aggregation-induced luminescence material TCBPE, resulting in its transformation into a green fluorescent probe. Through the multi-line analysis system, the detection sensitivity and accuracy of the sensor are improved. In brief, the sensor does not require complex antibody labeling and paired antibodies, and only one antibody is needed to complete the detection process.

A novel red-to-near-infrared AIE fluorescent probe for detection of Hg2+ with large Stokes shift in plant and living cells

Due to the highly toxic nature of mercury ions to living organisms, accurately detecting Hg2+ in water samples and biological systems is of great significance. In this study, we designed and synthesized a novel red-to-near-infrared Aggregation-Induced Emission (AIE) fluorescent probe (named as DS) based Fluorene derivatives on specifically for Hg2+ detection. Probe DS can visually identify Hg2+ through an red-to-near-infrared fluorescence enhancement change, characterized by a large Stokes shift (130 nm) and AIE feature. This probe offers a fast response, high selectivity and sensitivity. The Hg2+-induced deprotection reaction of the thioketal mechanism was thoroughly investigated using nuclear magnetic resonance spectroscopy (NMR), mass spectrometry (MS) and density functional theory (DFT) calculation. Additionly, dynamic light scattering (DLS) results indicated that the aggregation states changes of the molecular play a crucial role in the AIE fluorescence response of probe DS toward Hg2+. The red-to-near-infrared response with AIE feature not only avoids the interference of auto-fluorescence signals in complex environments, but also reduces the fluorescence quenching caused by probe molecular aggregation. This makes probe DS highly suitable for high-quality imaging detection of Hg2+ in aqueous environments. Furthermore, probe DS demonstrates the capability for visual fluorescence detection of Hg2+ concentrations in water sample, plant roots and living cells.

Semi-quantitative and visual detection of Cu2+ and glyphosate in real samples and living cells using fluorescent and colorimetric dual-signals peptide-based probe

The excessive emission of copper ions (Cu2+) and the abuse of glyphosate (Glyp) have caused serious harm to the ecological environment and human health, so it is important to develop a fast and convenient method for the analysis of Cu2+ and glyphosate to ensure environmental and food safety. Herein, a dual-signals peptide-based probe (FASRH) with fluorescent and colorimetric was prepared using 5-carboxyl fluorescein modified tetrapeptide (Ala-Ser-Arg-His-NH2). FASRH was successfully used to recognize Cu2+ as a fluorescence "on-off" probe, forming the FASRH-Cu2+ complex with non-fluorescence. As a new promising cascade probe, FASRH-Cu2+ complex probe has high selectivity (only Glyp), good sensitivity (50.2 nM), good anti-interference ability and wide pH range (7.0-11.0) for the detection of glyphosate by ligand replacement method. In addition, the recognizable color changed markedly under 365 nm UV light and natural light. Notably, FASRH not only achieved accurate monitoring of Cu2+ and glyphosate in two real water samples, but also successfully applied to detect Cu2+ and glyphosate in live Hacat cells based on low cytotoxicity. Moreover, it is worth noting that FASRH-impregnated test strips exhibited significant fluorescence and colorimetric color changes for Cu2+ and glyphosate via naked eye. Furthermore, smartphone-assisted FASRH was used for the portable detection of Cu2+ and glyphosate based on the advantages of simplicity, low cost and fast response.

Ratiometric peptide-based fluorescent probe with large Stokes shift for detection of Hg2+ and S2- and its applications in cells imaging and smartphone-assisted recognition

In this work, a new ratiometric fluorescent probe DKA was synthesized based on the double sides of lysine backbone conjugated with alanine and dansyl groups. DKA exhibited fluorescence ratiometric response for Hg2+ with high sensitivity (13.4 nM), specific selectivity (only Hg2+), strong anti-interference ability (no interference), fast recognition (within 60 s) and wide pH range (5-10). The stoichiometry of binding of DKA and Hg2+ was determined to be 1:1 via Job's plot, ESI-HRMS and 1HNMR titration analysis. Subsequently, the in situ formation of DKA-Hg2+ complex was used for highly selective detection of S2- as a novel fluorescence "on-off" probe, and the lowest detection limit for S2- was 12.9 nM. In addition, DKA possessed excellent cells permeation and low toxicity, and fluorescence imaging of Hg2+ and S2- was performed in living Hacat cells. Most importantly, the digital imaging using a smartphone color recognition APP indicated that DKA could semi-quantitatively and visually detected Hg2+ and S2- without expensive equipment.

Imaging gastrointestinal damage due to acute mercury poisoning using a mitochondria-targeted dual near-infrared fluorescent probe

Mercury (Hg) is one of the most widespread pollutants that pose serious threats to public health and the environment. People are inevitably exposed to Hg via different routes, such as respiration, dermal contact, drinking or diet. Hg poisoning could cause gingivitis, inflammation, vomiting and diarrhea, respiratory distress or even death. Especially during the developmental stage, there is considerable harm to the brain development of young children, causing serious symptoms such as intellectual disability and motor impairments, and delayed neural development. Therefore, it's of great significance to develop a specific, quick, practical and labor-saving assay for monitoring Hg2+. Herein, a mitochondria-targeted dual (excitation 700 nm and emission 728 nm) near-infrared (NIR) fluorescent probe JZ-1 was synthesized to detect Hg2+, which is a turn-on fluorescent probe designed based on the rhodamine fluorophore thiolactone, with advantages of swift response, great selectivity, and robust anti-interference capability. Cell fluorescence imaging results showed that JZ-1 could selectively target mitochondria in HeLa cells and monitor exogenous Hg2+. More importantly, JZ-1 has been successfully used to monitor gastrointestinal damage of acute mercury poisoning in a drug-induced mouse model, which provided a great method for sensing Hg species in living subjects, as well as for prenatal diagnosis.

A novel dual-responsive colorimetric/fluorescent probe for the detection of N2H4 and ClO- and its application in environmental analysis and bioimaging

Hydrazine (N2H4) and hypochlorite (ClO-) are both reactive chemical substances extensively utilized across various industrial domains. Excessive hydrazine (N2H4) and hypochlorite (ClO-) can pose significant risks to the environment, ecosystems, and human health. In order to assess and control the environmental hazard caused by N2H4 and ClO-, there is an imperative need for efficient methods capable of rapid and precise detection of these contaminants. This paper introduces a novel dual-responsive colorimetric/fluorescent probe (MDT) for the detection of N2H4 and ClO- in environmental and biological samples. The probe exhibits turn-on fluorescent responses to N2H4 or ClO- with low detection limits (N2H4: 8 nM; ClO-: 15 nM), large Stokes shifts (N2H4: 175 nm; ClO-: 203 nm), short response time (N2H4: 4 min; ClO-: 5 s) and broad pH range (5-10). In practical applications, MDT has been successfully employed in detecting N2H4 and ClO- in water and soil samples from diverse locations. Test strips loaded with MDT offer a visual and convenient means to track N2H4 vapor and quantify N2H4 and ClO- concentrations in solutions. Finally, MDT has been utilized for sensing N2H4 and ClO- in Arabidopsis thaliana roots and living zebrafish. This study presents a promising tool for monitoring N2H4 and ClO- in the environment and living organisms.

Naphthalimide-based fluorescent probe for Hg2+ detection and imaging in living cells and zebrafish

A simple naphthalimide-based fluorescent probe was designed and synthesized for the determination of mercury ion (Hg2+ ). The probe showed a noticeable fluorescence quenching response for Hg2+ . When added with Hg2+ , the fluorescence intensity of the probe at 560 nm was remarkably decreased with the color changed from yellow to colorless under ultraviolet (UV) light. The probe had a notable selectivity and sensitivity for Hg2+ and displayed an excellent sensing performance when detecting Hg2+ at low concentration (19.5 nM). The binding phenomenon between the probe and Hg2+ was identified by Job's method and high-resolution mass spectrometry (HRMS). Moreover, the probe was not only utilized to identify Hg2+ in real samples with satisfactory results (92.00%-110.00%) but also was successfully used for bioimaging in cells and zebrafish. The recognition mechanism has been verified by transmission electron microscopy (TEM) for the first time. All the results showed that the probe could be used as a potent useful tool for detection of Hg2+ .