Biothiols-activated near-infrared frequency up-conversion luminescence probe for early evaluation of drug-induced hepatotoxicity.

A novel biothiols-sensitive near-infrared (NIR) fluorescent probe RhDN based on a rhodamine skeleton was developed for early detection of drug-induced hepatotoxicity in living mice. RhDN can be used not only as a conventional large stokes shift fluorescent (FL) probe, but also as a kind of anti-Stokes frequency upconversion luminescence (FUCL) molecular probe, which represents a long wavelength excitation (808 nm) to short wavelength emission (760 nm), and response to Cys/Hcy/GSH with high sensitivity. Compared with traditional FL methods, the FUCL method exhibited a lower detection limit of Cys, Hcy, and GSH in 75.1 nM, 101.8 nM, and 84.9 nM, respectively. We exemplify RhDN for tracking endogenously biothiols distribution in living cells and further realize real-time in vivo bioimaging of biothiols activity in mice with dual-mode luminescence system. Moreover, RhDN has been successfully applied to visualize the detection of drug-induced hepatotoxicity in living mice. Overall, this report presents a unique approach to the development of large stokes shift NIR FUCL molecular probes for in vitro and in vivo biothiols biosensing.

A ratiometric fluorescent probe based on a novel fluorophore with high selectivity for imaging cysteine in living cells.

As a biothiol, cysteine (Cys) is essential to both physiological and pathological processes and has been associated with many diseases, including neurological disorders, rheumatoid arthritis, and renal dysfunction. Therefore, the development of a high-performance probe for detecting Cys levels can help prevent and diagnose disease. In this study, a ratiometric fluorescent probe based on a novel fluorophore was developed for detecting Cys, and it showed high specificity and a rapid response time toward Cys. This probe demonstrates excellent biocompatibility and has been utilized effectively for the imaging of Cys in living cells.

Development of a fluorous trapping reagent for rapid detection of electrophilic reactive metabolites.

A cysteine-based fluorous trapping reagent, Rf8CYS, was developed. Rf8CYS formed adducts with soft and hard electrophilic reactive metabolites. These fluorous-tagged adducts were purified via both fluorous solid-phase extraction and the direct injection method. The highly sensitive mass spectrometric detection of an unprecedented adduct of the ticlopidine metabolite was realized.

Using L-cysteine to enhance calibration range and prevent a memory effect in mercury analysis of complex samples via ICP-OES.

BACKGROUND: Mercury (Hg) is a persistent pollutant occurring in the environment able to transition between different species. It can therefore be found in air, soil and water reservoirs becoming a present concern for the general population but also sensitive populations like pregnant women. Therefore, investigating organ-specific transfer mechanisms of Hg is mandatory for Hg toxicity testing. For this, an in vitro system using microporous inserts to monitor the transfer across an in vitro placental barrier has been used. However, due to the cytotoxicity of Hg only low concentrations (1.26 ×10-4 - 1.36 ×10-2 µg/µL Hg) can be applied, making Hg determination in cell culture medium using inductively coupled plasma-optical emission spectrometry challenging, especially when these trace amounts should be determined alongside other trace elements which are naturally occurring in cells and cell culture medium like the essential metals manganese (Mn), iron (Fe), copper (Cu), and zinc (Zn). Additionally, Hg analysis on an ICP system holds also a number of challenges like a persistent memory effect and instability of Hg standard solutions. METHODS: The development of a rapid and sensitive ICP-OES method to determine Hg in different matrices like cell culture medium and cells has been performed on an Avio 220 Max ICP-OES (Perkin-Elmer) equipped with a cyclonic spray chamber and MicroMist® nebulizer. Cell lysates and cell culture medium were diluted in a mixture of 0.2 % L-cysteine, 2 % HNO3 and 0.1 % HCl and directly introduced into the ICP-OES system. Further method development included the suitability of the analysis of multiple elements like Mn, Fe, Cu, and Zn as well as the determination of the limit of detection and limit of quantification. RESULTS: The combination of 0.2 % L-cysteine, 2 % HNO3 and 0.1 % HCl is able to bind and stabilize Hg ions in standard solutions and in biological matrices over a wide dynamic concentration range (1 - 500 µg/L) also alongside other metals like Mn, Fe, Cu and Zn without losses of sensitivity. A short run time of 3 min enables high throughput analysis. Additionally, the high salt and carbon concentrations in the culture medium do not affect Hg sensitivity using the ICP-OES. CONCLUSION: This method is a useful tool for the quantification of Hg in a variety of complex matrices including cells and cell culture media (high salt and carbon-rich (∼1 % each)) with high sensitivity and minimal sample preparation allowing high throughput. Furthermore, not only Hg can be determined in biological matrices, but even multiple elemental analysis can be carried out to address the effect of Hg on other metals homeostasis.

A metal-phenolic coordination framework nanozyme exhibits dual enzyme mimicking activity and its application is effective for colorimetric detection of biomolecules.

Biomolecules play vital roles in many biological processes and diseases, making their identification crucial. Herein, we present a colorimetric sensing method for detecting biomolecules like cysteine (Cys), homocysteine (Hcy), and glutathione (GSH). This approach is based on a reaction system whereby colorless 3,3',5,5'-tetramethylbenzidine (TMB) undergoes catalytic oxidation to form blue-colored oxidized TMB (ox-TMB) in the presence of hydrogen peroxide (H2O2), utilizing the peroxidase and catalase-mimicking activities of metal-phenolic coordination frameworks (MPNs) of Cu-TA, Co-TA, and Fe-TA nanospheres. The Fe-TA nanospheres demonstrated superior activity, more active sites and enhanced electron transport. Under optimal conditions, the Fe-TA nanospheres were used for the detection of biomolecules. When present, biomolecules inhibit the reaction between TMB and H2O2, causing various colorimetric responses at low detection limits of 0.382, 0.776 and 0.750 µM for Cys, Hcy and GSH. Furthermore, it was successfully applied to real water samples with good recovery results. The developed sensor not only offers a rapid, portable, and user-friendly technique for multi-target analysis of biomolecules at low concentrations but also expands the potential uses of MPNs for other targets in the environmental field.

Hydrazone-linked covalent organic framework functionalized with cysteine as a fluorescence sensor and Exploration of paper chip for p-nitrophenol detection.

The large use and emission of p-nitrophenol (p-NP) seriously pollute the environment and endanger human health. In this work, a hydrazone-linked fluorescent covalent organic framework (BATHz-COF) was simply synthesized at room temperature and covalently linked N-acetyl-L-cysteine (NALC) via the "thiol-ene" click reaction, where carboxyl groups were introduced to improve dispersion and fluorescence intensity. As a rapid, good selectivity and reusability fluorescence sensor, the obtained COF-NALC has been used for quantitative analysis of p-NP predicated on the internal filtering effect (IFE). Under optimal conditions, COF-NALC enabled quantitative detection of p-NP with a linear range of 5-50 µM and the detection limit was 1.46 µM. The application of COF-NALC to the detection of p-NP in river water samples was successful, and the satisfactory recoveries were 98.0%-109.3%. Furthermore, the fluorescent COF paper chips constructed by in situ growth were combined with a smartphone to build a visual platform for the quick and real-time detection of p-NP, providing an excellent illustration for the development of intelligent fluorescence sensing in environmental analysis.

Efficient turn-on fluorescent probe cooperated by cascade response for disclosing the fluctuation of cysteine in cells.

BACKGROUND: The research on cysteine (Cys) determination is deemed as a hot topic, since it has been reported to be connected with various physiological processes and disease prediction. However, existing Cys-responding probes may expose some defects such as long reaction time, disappointing photostability, and suboptimal sensitivity. Under such a circumstance, our team has proposed an efficient fluorescent probe with novel sensing mechanism to perfectly cope with the above-mentioned drawbacks. RESULTS: A novel cascade reaction-based probe 9-(2,2-dicyanovinyl)-2,3,6,7-tetrahydro-1H,5H-pyrido[3,2,1-ij]quinolin-8-yl acrylate (DPQA) has been synthesized for the first time. Undergoing addition-cleavage and cyclization-rearrangement processes, DPQA reacts with Cys to generate an iminocoumarin product with relucent green fluorescence, namely 11-imino-2,3,6,7-tetrahydro-1H,5H,11H-pyrano[2,3-f]pyrido[3,2,1-ij]quinoline-10-carbonitrile (IMC-J), and the relative fluorescence quantum yield (Φf) soars from 0.007 to 0.793. Utilizing such a mechanism, DPQA shows a superb turn-on signal (172-fold), low detection limit (4.1 nM), and wide detection range (5-6000 nM) toward Cys detection. Encouraged by the admirable sensing performance of DPQA, bioimaging of endogenous Cys has been attempted in HeLa cells with satisfactory results. Moreover, cell model of H2O2-induced oxidative stress has been established and the Cys fluctuation during this process has been inspected, elucidating how living cells confront with the eruption of reactive oxygen species (ROS) storm. SIGNIFICANCE: The probe DPQA with such an intriguing cascade responding process for Cys detection has been endowed with many merits, such as fast reaction and superior sensitivity, conducive to improving responsiveness and rendering it more suitable for further applications. Thereby, we expect that the DPQA would be an efficient tool for detecting Cys fluctuation in living cells of different physiological processes.

Electrochemical and quantum chemical approaches to the study of dopamine sensing using bentonite and l-cysteine modified carbon paste electrode.

This work presents a significant investigation involving both electrochemical experiment and quantum chemical simulation approaches. The objective was to characterize the electrochemical detection of dopamine (DA). The detection was carried out using a modified carbon paste electrode (CPE) incorporating bentonite (Bent) and l-cysteine (CySH) (named as CySH/Bent/CPE). To understand and explain the oxidation mechanism of DA on the CySH/Bent modified electrode surface, the coupling of the two approaches were exploited. The CySH/Bent/CPE showed excellent electroactivity toward DA such as good sensibility, selectivity, stability, and regenerative ability. The developed sensor shows a dynamic linear range from 0.8 to 80 µM with a limit of detection and quantification of 0.5 µM and 1.5 µM, respectively. During the quantitative analysis of DA in presence of ascorbic acid (AA) and uric acid (UA) the electrochemical oxidation signals of AA, DA, and UA distinctly appear as three separate peaks. The potential differences between the peaks are 190 mv, 150 mv, and 340 mV for the AA-DA, DA-UA, and AA-UA oxidation pairs, respectively. These observations stem from square wave voltammetry (SWV) studies, along with the corresponding redox peak potential separations. The developed sensor is simple and accurate to monitor DA in human serum samples. On the other hand, CySH acts as an electrocatalyst on the CySH/Bent/CPE surface by increasing its active electron transfer sites, as suggested by the quantum chemical modeling with analytical results of Fukui. Furthermore, the voltammetric results obtained agree well with the theoretical calculations.

Active site-tuned high peroxidase-like activity nanozyme for on-the-spot detection of saliva total antioxidant capacity using smartphone devices.

Metal-Organic Framework (MOF) based nanozymes with clear structure are beneficial for exploration of structural-performance and exhibit broad prospects in improving activity. In this study, the prepared bimetallic Fe3Ni-MOF nanozyme was superior to single metal MOF in the peroxidase-like activity. Subsequently, a derivative nanozyme (Fe3Ni-MOF-Ar) was prepared by pyrolysis using Fe3Ni-MOF as the precursor in argon atomoshere with controlled temperature. The investigated of Fe3Ni-MOF-Ar revealed that the irregular macroporous state and the presence of heterovalent FeIII/FeII sites of Fe3Ni-MOF-Ar enable the retention, exposure, and electronic structure regulation of active sites, promoting the dual mechanism (the generation of •OH and electron transfer mechanism) and significantly increasing the peroxidase-like activity. Fe3Ni-MOF-Ar exhibited a strong affinity for substrate H2O2, which is higher than horseradish peroxidase. Ascorbic acid and cysteine are typical substances of antioxidants. Fe3Ni-MOF-Ar was used for sensitive colorimetric detection of ascorbic acid and cysteine, and the detection limit was as low as 150 and 60 nM. In addition, the smartphone devices was used to detection of antioxidant equivalent ascorbic acid, with a detection range of 0.5-120 µM. Fe3Ni-MOF-Ar nanozyme is feasible for sensitive detection of saliva total antioxidant capacity.

Sensitive SERS assay for L-cysteine based on functionalized silver nanoparticles.

L-cysteine, an indispensable amino acid present in natural proteins, plays pivotal roles in various biological processes. Consequently, precise and selective monitoring of its concentrations is imperative. Herein, we propose a Surface-enhanced Raman Scattering (SERS) sensor for detecting L-cysteine based on the anti-aggregation of 4-mercaptobenzoic acid (4-MBA) and histidine (His) functionalized silver nanoparticles (Ag NPs). The presence of Hg2+ ions can induce the aggregation of Ag NPs@His@4-MBA due to the unique nanostructures of Ag NPs@His@4-MBA, resulting in a robust SERS intensity of 4-MBA. However, in the presence of L-cysteine, the stronger affinity between L-cysteine and Hg2+ reduces the concentration of free Hg2+, causing the dispersion of the aggregated functionalized Ag NPs and the reduction of the SERS signal intensity of 4-MBA. The developed SERS platform demonstrates excellent performance with a low detection limit of 5 nM (S/N = 3) and linear detection capabilities within the range of 0.01-100 µM for L-cysteine. Additionally, the method was successfully employed for the determination of L-cysteine in spiked serum samples, yielding recoveries ranging from 95.0 % to 108.1 % with relative standard deviations of less than 3.3 %. This study not only presents a novel approach for fabricating highly sensitive and specific SERS biosensors for biomolecule detection but also offers a significant strategy for the development and construction of SERS substrates using anti-aggregation design.

Old drug, new use: The thalidomide-based fluorescent probe for cysteine detection and imaging in living cells.

Thalidomide, as a high-profile cereblon (CRBN) ligand, has attracted much attention because of its ability to target protein degradation. In this study, we are committed to developing a new fluorescent probe THD-1 based on thalidomide, aiming at improving the performance of cysteine fluorescent probe in optical properties and biocompatibility. The experimental results showed that THD-1, as a cysteine fluorescent probe, owned the characteristics of obvious colorimetric change, fast response time, good selectivity and high sensitivity. The mechanism of THD-1 sensing cysteine was further verified to ensure its reliability and effectiveness. It was also worth mentioning that THD-1 was successfully applied to the biological imaging of cysteine in living A549 cells, which highlighted its value in practical application. Overall, thalidomide, as a clinically approved drug, not only enriches the fluorescent skeleton library, but also paves a new way for the further development of fluorescent probes.

A Mass Spectrometry Strategy for Protein Quantification Based on the Differential Alkylation of Cysteines Using Iodoacetamide and Acrylamide.

Mass spectrometry has become the most prominent yet evolving technology in quantitative proteomics. Today, a number of label-free and label-based approaches are available for the relative and absolute quantification of proteins and peptides. However, the label-based methods rely solely on the employment of stable isotopes, which are expensive and often limited in availability. Here we propose a label-based quantification strategy, where the mass difference is identified by the differential alkylation of cysteines using iodoacetamide and acrylamide. The alkylation reactions were performed under identical experimental conditions; therefore, the method can be easily integrated into standard proteomic workflows. Using high-resolution mass spectrometry, the feasibility of this approach was assessed with a set of tryptic peptides of human serum albumin. Several critical questions, such as the efficiency of labeling and the effect of the differential alkylation on the peptide retention and fragmentation, were addressed. The concentration of the quality control samples calculated against the calibration curves were within the ±20% acceptance range. It was also demonstrated that heavy labeled peptides exhibit a similar extraction recovery and matrix effect to light ones. Consequently, the approach presented here may be a viable and cost-effective alternative of stable isotope labeling strategies for the quantification of cysteine-containing proteins.

A two-photon fluorescent probe for highly selective detection of Cys over GSH and Hcy based on the Michael addition and transcyclization mechanism and its application in bioimaging and protein straining in SDS-PAGE.

BACKGROUND: Cysteine (Cys), glutathione (GSH), and homocysteine (Hcy), as three major biothiols are involved in a variety of physiological processes and play a crucial role in plant growth. Abnormal levels of Cys can cause plants to fail to grow properly. To date, although a very large number of fluorescent probes have been reported for the detection of biothiols, very few of them can be used for the selective discrimination of Cys from GSH and Hcy due to their structural similarity, and only a few of them can be used for plant imaging. RESULTS: Here, three fluorescent probes (o-/m-/p-TMA) based on TMN fluorophore and the ortho-/meta-/para-substituted maleimide recognition groups were constructed to investigate the selective response effect of Cys. Compared to the o-/m-TMA, p-TMA can selectively detect Cys over GSH and Hcy with a rapid response time (10 min) and a low detection limit (0.26 µM). The theoretical calculation confirmed that the intermediate p-TMA-Cys-int has shorter interatomic reaction distances (3.827 Å) compared to o-/m-TMA-Cys (5.533/5.287 Å), making it more suitable for further transcyclization reactions. Additionally, p-TMA has been employed for selective tracking of exogenous and endogenous Cys in Arabidopsis thaliana using both single-/two-photon fluorescence imaging. Furthermore, single cell walls produced obvious two-photon fluorescence signals, indicating that p-TMA can be used for high-concentration Cys analysis in single cells. Surprisingly, p-TMA can be used as a fluorescent dye for protein staining in SDS-PAGE with higher sensitivity (7.49 µg/mL) than classical Coomassie brilliant blue (14.11 µg/mL). SIGNIFICANCE: The outstanding properties of p-TMA make it a promising multifunctional molecular tool for the highly selective detection of Cys over GSH and Hcy in various complex environments, including water solutions, zebrafish, and plants. Additionally, it has the potential to be developed as a fluorescent dye for a simple and fast SDS-PAGE fluorescence staining method.

Acidic Derivatization of Thiols Using Diethyl 2-Methylenemalonate: Thiol-Michael Addition Click Reaction for Simultaneous Analysis of Cysteine and Cystine in Culture Media Using LC-MS/MS.

Cysteine (Cys) and its oxidized form, cystine (Cys2), play crucial roles in biological systems and have considerable applications in cell culture. However, Cys in cell culture media is easily oxidized to Cys2, leading to solubility issues. Traditional analytical methods struggle to maintain the oxidation states of Cys and Cys2 during analysis, posing a significant challenge to accurately measuring and controlling these compounds. To effectively control the Cys and Cys2 levels, a rapid and accurate analytical method is required. Here, we screened derivatizing reagents that can react with Cys even under acidic conditions to realize a novel analytical method for simultaneously determining Cys and Cys2 levels. Diethyl 2-methylenemalonate (EMM) was found to possess the desired traits. EMM, characterized by its dual electron-withdrawing attributes, allowed for a rapid reaction with Cys under acidic conditions, preserving intact information for understanding the functions of target compounds. Combined with LC-MS/MS and an internal standard, this method provided high analytical accuracy in a short analytical time of 9 min. Using the developed method, the rapid oxidation of Cys in cell culture media was observed with the headspace of the storage container considerably influencing Cys oxidation and Cys2 precipitation rates. The developed method enabled the direct and simplified analysis of Cys behavior in practical media samples and could be used in formulating new media compositions, ensuring quality assurance, and real-time analysis of Cys and Cys2 in cell culture supernatants. This novel approach holds the potential to further enhance the media performance by enabling the timely optimal addition of Cys.

Smartphone-assisted mobile fluorescence sensor for self-calibrated detection of anthrax biomarker, Cu2+, and cysteine in food analysis.

Dipicolinic acid (DPA), as a biomarker for Bacillus anthracis, is highly toxic at trace levels. Rapid and on-site quantitative detection of DPA is essential for maintaining food safety and public health. This work develops a dual-channel self-calibrated fluorescence sensor constructed by the YVO4:Eu and Tb-ß-diketone complex for rapid visual detection of DPA. This sensor exhibits high selectivity, fast response time, excellent detection sensitivity, and the detection limit is as low as 4.5 nM in the linear range of 0-16 µM. A smartphone APP and portable ultraviolet lamp can assemble a mobile fluorescence sensor for on-site analysis. Interestingly, adding Cu2+ ions can quench the fluorescence intensity of Tb3+. In contrast, the addition of cysteine can restore the fluorescence, allowing the accurate detection of Cu2+ ions and cysteine in environmental water and food samples. This work provides a portable sensor that facilitates real-time analysis of multiple targets in food and the environment.

Multifunctional fluorescent probe for simultaneous revealing Cys and ONOO- dynamic correlation in the ferroptosis.

Ferroptosis is a type of lipid peroxidation-induced apoptosis brought on by imbalances in iron metabolism and redox. It involves both the thiol-associated anti-ferroptosis pathway and the excessive buildup of reactive oxygen species (ROS), which stimulates the ferroptosis pathway. Determining the precise control mechanism of ferroptosis requires examining the dynamic connection between reactive sulfur species (RSS) and ROS. Cysteine (Cys) and peroxynitrite (ONOO-) are highly active redox species in organisms and play dynamic roles in the ferroptosis process. In this study, a coumarin dye was conjugated with specific response sites for Cys and ONOO-, enabling the simultaneous detection of Cys and ONOO- through the green and red fluorescence channels, respectively (λem = 498 nm for Cys and λem = 565 nm for ONOO-). Using the probe LXB, we monitored the changes in Cys and ONOO- levels in the ferroptosis pathway induced by erastin. The results demonstrate a significant generation of ONOO- and a noticeable decrease in intracellular Cys levels at the beginning upon erastin treatment and finally maintains a relatively low level. This study presents the first probe to investigate the intracellular redox modulation and control between Cys and ONOO- during ferroptosis, providing valuable insights into the potential mutual correlation between Cys and ONOO- in this process.

Two spirobifluene-based turn-on fluorescent probes for highly selective detection of Cysteine and the applications in cells two-photon fluorescence imaging.

Two spirobifluene-based fluorescent probes SPF1 and SPF2, were designed and synthesized. The probes displayed "turn-on" fluorescence response for Cysteine. One of the challenges in developing a Cysteine probe is to secure high selectivity. SPF1/SPF2 can discriminate Cysteine from GSH as well as Hcy, and showed high substrate selectivity. The detection limit of SPF1 is 36 nM, which is excellent comparing with other optical sensors for Cysteine. The sensing mechanism of SPF1/SPF2 was verified by experimental data and theoretical calculations. There was a good linear relationship between the fluorescence intensity of SPF1/SPF2 and the concentration of Cysteine. The MTT tests indicated that SPF1/SPF2 had low cytotoxicity and good biocompatibility. Theoretical calculations demonstrated that SPF1, SPF2, and their related reaction products with Cysteine exhibited good two-photon absorption properties. Finally, SPF1/SPF2 had been successfully applied to the imaging of Cysteine in living cells under two-photon excitation.

An AND-Gate Photoacoustic Probe for Cys and H2S Precise Photoacoustic Sensing in Localized Tumors.

Photoacoustic (PA) tomography has shown many promising aspects in noninvasive and precise imaging of deep-localized biomarkers. However, these traditional single-locked PA probes always face challenges in precise PA imaging with high specificity. Here, we report a novel AND-gate photoacoustic probe, BAE, to improve tumor imaging accuracy via the combination of two tumor-associated biomarkers, cysteine (Cys) and hydrogen sulfide (H2S). Only when Cys and H2S are concurrently introduced into the detection system does the absorption of BAE red-shift from the initial 680 to 810 nm, thereby showing a 5.29-fold enhancement in its PA signal at 810 nm. The good specificity of BAE is proven, since an obvious PA signal could be observed only in the solution containing both Cys and H2S and was not affected by other reactive sulfur species. After being taken up by tumors with the assistance of a nanomicelle, the AND-gate PA probe BAE was applied for dynamic real-time monitoring of Cys and H2S in vivo, achieving precise identification of tumors. This AND-gate PA probe provides a potential technical tool for precise sensing analysis of deep-seated diseases.

Dual-functional porphyrinic zirconium-based metal-organic framework for the fluorescent sensing of histidine enantiomers and Hg2.

A novel fluorescence sensor based on a porphyrinic zirconium-based metal-organic framework, L-cysteine-modified PCN-222 (L-Cys/PCN-222), was developed to selectively recognize histidine enantiomers and sensitively detect Hg2+. The dual-functional sensor was successfully prepared via the solvent-assisted ligand incorporation method and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), 1H nuclear magnetic resonance (1H NMR) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, circular dichroism (CD), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption-desorption analyses. L-Cys/PCN-222 not only showed a higher quenching response for L-histidine than that for D-histidine with a fast fluorescent response rate of <40 s but also exhibited low detection limits for L- and D-histidine (2.48 µmol L-1 and 3.85 µmol L-1, respectively). Moreover, L-Cys/PCN-222 was employed as a fluorescent and visual sensor for the highly sensitive detection of Hg2+ in the linear range of 10-500 µmol L-1, and the detection limit was calculated to be 2.79 µmol L-1 in surface water. The specific and selective recognition of chiral compounds and metal ions by our probe make it suitable for real field applications.

l-Cysteine-Tuned the Hierarchical Structure Based on Benzimidazole: Synthesis, Characterization, and Application in Ratiometric Electrochemiluminescence Immunoassay.

Efficient and robust electrochemiluminescence (ECL) emitters are crucial for enhancing the ECL immunosensor sensitivity. This study introduces a novel ECL emitter, CoBIM/Cys, featuring a hierarchical core-shell structure. The core of the structure is created through the swift coordination between the sulfhydryl and carboxyl groups of l-cysteine (l-Cys) and cobalt ions (Co2+), while the shell is constructed by sequentially coordinating benzimidazole (BIM) with Co2+. This design yields a greater specific surface area and a more intricate porous structure compared to CoBIM, markedly enhancing mass transfer and luminophore accessibility. Moreover, the l-Cys and Co2+ core introduces Co-S and Co-O catalytic sites, which improve the catalytic decomposition of H2O2, leading to an increased production of hydroperoxyl radicals (OOH•). This mechanism substantially amplifies the ECL performance. Leveraging the competitive interaction between isoluminol and BIM for OOH• during ECL emission, we developed a ratiometric immunosensor for cardiac troponin I (cTnI) detection. This immunosensor demonstrates a remarkably broad detection range (1 pg mL-1 to 10 ng mL-1), a low detection limit (0.4 pg mL-1), and exceptional reproducibility and specificity.