Dual-Site Chemosensor for Monitoring ·OH-Cysteine Redox in Cells and In Vivo

Coumarin-aurone based fluorescence probes for cysteine sensitive in-situ identification in living cells

The quantification of cysteine (Cys) levels in the organisms holds paramount significance in biological research and disease diagnosis, which can give the correlation between abnormal Cys levels and diseases. In this study, two fluorescent probes, designated as DEA-OH and DEA-AC, featuring a coumarin-aurone backbone specifically engineered for Cys detection, were meticulously designed and synthesized. The diethylamino coumarin-aurone probe DEA-OH and the acrylate-substituted probe DEA-AC demonstrated remarkable sensitivity in detecting cysteine by means of copper displacement (DEA-OH) and acrylate hydrolysis mechanisms (DEA-AC) with fluorescence detection limits of 7.25 μM and 1.65 μM, respectively. Moreover, the fluorescence peak wavelength of the two probes displayed a linear relationship with solvent polarity in the ET (30) range of 30-65 kcal•mol-1, indicating the potential for monitoring changes in environmental polarity within this ET (30) range. The outstanding attributes exhibited by DEA-AC including superior photostability, remarkable selectivity, and swift response (kinetic rate constant: 0.00747 s-1), coupled with the exceptional anti-interference ability, have significantly broadened its scope of applications, for example detecting alterations in Cys within biological systems.

A fluorescent probe for detecting bisulfite/sulfite in lipid droplets and tracking the dynamics of lipid droplets

Intracellular lipid droplets (LDs) are important organelles regulating intracellular redox processes. Endogenous bisulfite/sulfite (HSO3-/SO32-) is one of the metabolites of thiol metabolism. The variation in HSO3-/SO32- content around LDs is closely related to cellular homeostasis. However, there is currently no effective method to visualize and quantify the dynamic changes in HSO3-/SO32- content around LDs. In this work, a fluorescent probe MC-BEN utilizing a triphenylamine basic framework was developed to selectively recognize HSO3-/SO32- via a nucleophilic addition reaction. The probe exhibits excellent anti-interference capability, short response time, outstanding photostability, and a low fluorescence detection limit (6.1 μM) for HSO3-/SO32- recognition. More interesting, there is a trend of accelerated contact between LDs and lysosomes after MC-BEN targeting LDs and reacting with endogenous/exogenous HSO3-/SO32-, which may provide new ideas for the study of intracellular lysosomal lipophagy.

Sulfur-based fluorescent probes for biological analysis: A review

The widespread adoption of small-molecule fluorescence detection methodologies in scientific research and industrial contexts can be ascribed to their inherent merits, including elevated sensitivity, exceptional selectivity, real-time detection capabilities, and non-destructive characteristics. In recent years, there has been a growing focus on small-molecule fluorescent probes engineered with sulfur elements, aiming to detect a diverse array of biologically active species. This review presents a comprehensive survey of sulfur-based fluorescent probes published from 2017 to 2023. The diverse repertoire of recognition sites, including but not limited to N, N-dimethylthiocarbamyl, disulfides, thioether, sulfonyls and sulfoxides, thiourea, thioester, thioacetal and thioketal, sulfhydryl, phenothiazine, thioamide, and others, inherent in these sulfur-based probes markedly amplifies their capacity for detecting a broad spectrum of analytes, such as metal ions, reactive oxygen species, reactive sulfur species, reactive nitrogen species, proteins, and beyond. Owing to the individual disparities in the molecular structures of the probes, analogous recognition units may be employed to discern diverse substrates. Subsequent to this classification, the review provides a concise summary and introduction to the design and biological applications of these probe molecules. Lastly, drawing upon a synthesis of published works, the review engages in a discussion regarding the merits and drawbacks of these fluorescent probes, offering guidance for future endeavors.

A selective mitochondria-targeted fluorescent probe for imaging cysteine in drug-induced liver injury

Cysteine (Cys) is involved in many physiological processes. It's challenging to detect Cys selectively as it has similar chemical structure with other biothiols such as homocysteine (Hcy) and glutathione (GSH). In this work, a novel fluorescence probe toward mitochondrial cysteine, HPXI-6C, has been developed by employing carbonate as a new recognizing unit and hemicyanine as a chromophore. HPXI-6C exhibits a high selectivity to Cys over hydrogen sulfide, homocysteine and glutathione. The limit of detection toward Cys was determined to be 42 nM. HPXI-6C can localize in mitochondria and produce strong fluorescence peaked at 725 nm in response to Cys in tumor cells. The uptake and generation pathways of Cys in acetaminophen hepatotoxicity cells was revealed by using HPXI-6C. HPXI-6C has been successfully applied in imaging of Cys in drug-induced liver injury in vivo. The research demonstrated that HPXI-6C is powerful in monitoring Cys and is conducive to the early diagnosis of drug-induced liver injury diseases.

Red-Light Triggered H-Abstraction Photoinitiators for the Efficient Oxygen-Independent Therapy of Hypoxic Tumors

The clinical application of photodynamic therapy (PDT) is limited by oxygen-dependence and side effects caused by photosensitizer residues. Photoinitiators based on the H-abstraction reaction can address these challenges because they can generate alkyl radical-killing cells independently of oxygen and undergo rapid bleaching following H-abstraction. Nonetheless, the development of photoinitiators for PDT has been impeded by the absence of effective design strategies. Herein, we have developed aryl-ketone substituted cyanine (ACy-R), the first red-light triggered H-abstraction photoinitiators for hypoxic cancer therapy. These ACy-R molecules inherited the near-infrared absorption of cyanine dye, and aryl-ketone modification imparted H-abstraction capability. Experimental and quantum calculations revealed that modifying the electron-withdrawing groups of the aryl (e.g., ACy-5F) improved the contribution of the O atom to the photon excitation process promoting intersystem crossing and H-abstraction ability. Particularly, ACy-5F rapidly penetrated cells and enriched in the endoplasmic reticulum. Even under severe hypoxia, ACy-5F initiated red-light induced H-abstraction with intracellular biomolecules, inducing necroptosis and ferroptosis. Moreover, ACy-5F was degraded after H-abstraction, thus avoiding the side effects of long-term phototoxicity after therapy. This study not only provides a crucial molecular tool for hypoxic tumors therapy, but also presents a promising strategy for the development of multifunctional photosensitizers and photoinitiators.

A Review on Recent Development of Phenothiazine-Based Chromogenic and Fluorogenic Sensors for the Detection of Cations, Anions, and Neutral Analytes

This review provides an in-depth examination of recent progress in the development of chemosensors, with a particular emphasis on colorimetric and fluorescent probes. It systematically explores various sensing mechanisms, including metal-to-ligand charge transfer (MLCT), ligand-to-metal charge transfer (LMCT), photoinduced electron transfer (PET), intramolecular charge transfer (ICT), and fluorescence resonance energy transfer (FRET), and elucidates the mechanism of action for cation and anion chemosensors. Special attention is given to phenothiazine-based fluorescence probes, highlighting their exceptional sensitivity and rapid detection abilities for a broad spectrum of analytes, including cations, anions, and small molecules. Phenothiazine chemosensors have emerged as versatile tools widely employed in a multitude of applications, spanning environmental and biomedical fields. Furthermore, it addresses existing challenges and offers insights into future research directions, aiming to facilitate the continued advancement of phenothiazine-based fluorescent probes.

Fast and easy detection of hypochlorite by a smartphone-based fluorescent turn-on probe: Applications to water samples, zebrafish and plant imaging

We have developed a fluorescent probe DBT-Cl ((E)-2-(2-(4-(diphenylamino)benzylidene) hydrazinyl)-N,N,N-trimethyl-2-oxoethan-1-aminium chloride) for ClO- with an aggregation-induced emission (AIE) strategy depending on solvent polarity. DBT-Cl possessed a prominent solvatochromic emission property with intramolecular charge transfer (ICT) from the TPA (triphenylamine) to the amide group, which was studied by spectroscopic analysis and DFT calculations. These unique AIE properties of DBT-Cl led to the recognition of ClO- with high fluorescent selectivity. DBT-Cl quickly detected ClO- in less than 1 sec with a fluorescent color change from green to cyan. DBT-Cl had a low detection limit of 9.67 μM to ClO-. Detection mechanism of DBT-Cl toward ClO- was illustrated to be oxidative cleavage of DBT-Cl by 1H NMR titrations, ESI-mass, and DFT calculations. We established the viability for dependable detection of ClO- in actual water samples, as well as zebrafish and plant imaging. In particular, DBT-Cl was capable of easily monitoring ClO- through a smartphone application. Therefore, DBT-Cl assured a promising approach for a fast-responsive and multi-applicable ClO- probe in environmental and living organism systems.

Simultaneous detection of cysteine and glutathione in food with a two-channel near-infrared fluorescent probe

L-Cysteine (Cys) and glutathione (GSH) are closely related biological species that widely exist in food and living cells. To simultaneously detect Cys and GSH from different emission channels, we developed a fluorescent probe (BDP-NBD) based on near-infrared BODIPY and 7-nitrobenzofurazan (NBD). Upon nucleophilic substitution reaction with GSH, BDP-NBD generated an emission band at 713 nm, which can be used to determine GSH (0-100 μM) with a low detection limit (34 nM). Different from GSH, BDP-NBD underwent a nucleophilic substitution-rearrangement reaction with Cys, affording two emission bands at 550 nm and 713 nm, respectively. BDP-NBD was successfully employed to quantify Cys and GSH in various food samples with good recoveries (86.6%-104.6%). Besides, BDP-NBD can image Cys and GSH in living cells from two emission channels. Therefore, this work developed a tool for the simultaneous determination of Cys and GSH in both food and living cells so as to ensure food safety and human health.

Dual-Site Chemosensor for Visualizing •OH-GSH Redox and Tracking Ferroptosis-Inducing Pathways In Vivo

Oxidative stress, characterized by an imbalance between oxidative and antioxidant processes, results in excessive accumulation of intracellular reactive oxygen species. Among these responses, the regulation of intracellular hydroxyl radicals (•OH) and glutathione (GSH) is vital for physiological processes. Real-time in situ monitoring these two opposing bioactive species and their redox interactions is essential for understanding physiological balance and imbalance. In this study, we developed a dual-site fluorescence chemosensor OG-3, which can independently image both exogenous and endogenous •OH and GSH in separate channels both within cells and in vivo, eliminating issues of spatiotemporal inhomogeneous distribution and cross-interference. With its imaging capabilities of monitoring •OH-GSH redox, OG-3 elucidated two different pathways for ferroptosis induction: (i) inhibition of system xc- to block cystine uptake (extrinsic pathway) and (ii) GPX4 inactivation, leading to the loss of antioxidant defense (intrinsic pathway). Moreover, we assessed the antiferroptotic function and effects of ferroptosis inhibitors by monitoring •OH and GSH fluctuations during ferroptosis. This method provides a reliable platform for identifying potential ferroptosis inhibitors, contributing to our understanding of relevant metabolic and physiological mechanisms. It shows potential for elucidating the regulation of ferroptosis mechanisms and investigating further strategies for therapeutic applications.

Biosensing of Cysteine through the Induction of Oxygen Vacancies in a Cu/Zr Heterostructure Prepared by Supercritical Antisolvent Technique

There has been a growing emphasis on facile preparation of binary heterogeneous composite materials. Leveraging the eco-friendly efficiency of supercritical CO2 technology, we achieved precise control over the influencing factors of mass transfer, enabling the accurate modulation of the resulting product morphology and properties. In the current study, CuxO/ZrOy composite materials were prepared using this technology and calcined to obtain electrode materials for the detection of cysteine (Cys). Essential comprehensive characterization techniques were employed to elucidate the heterojunction. The resulting electrode demonstrated a linear response to Cys within a concentration range of 0.5 nM to 1 μM, featuring a high sensitivity of 1035 μA·cm-2·μM-1 and a low detection limit of 97.3 nM. Thus, establishing a novel avenue for nonenzyme-based electrochemical sensors tailored for biologically active Cys detection through the implementation of a heterogeneous structure.

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.

Constructing a Hydrophilic Microsensor for High-Antifouling Neurotransmitter Dopamine Sensing

Real-time sensing of dopamine is essential for understanding its physiological function and clarifying the pathophysiological mechanism of diseases caused by impaired dopamine systems. However, severe fouling from nonspecific protein adsorption, for a long time, limited conventional neural recording electrodes concerning recording stability. This study reported a high-antifouling nanocrystalline boron-doped diamond microsensor grown on a carbon fiber substrate. The antifouling properties of this diamond sensor were strongly related to the grain size (i.e., nanocrystalline and microcrystalline) and surface terminations (i.e., oxygen and hydrogen terminals). Experimental observations and molecular dynamics calculations demonstrated that the oxygen-terminated nanocrystalline boron-doped diamond microsensor exhibited enhanced antifouling characteristics against protein adsorption, which was attributed to the formation of a strong hydration layer as a physical and energetic barrier that prevents protein adsorption on the surface. This finally allowed for in vivo monitoring of dopamine in rat brains upon potassium chloride stimulation, thus presenting a potential solution for the design of next-generation antifouling neural recording sensors. Experimental observations and molecular dynamics calculations demonstrated that the oxygen-terminated nanocrystalline boron-doped diamond (O-NCBDD) microsensor exhibited ultrahydrophilic properties with a contact angle of 4.9°, which was prone to forming a strong hydration layer as a physical and energetic barrier to withstand the adsorption of proteins. The proposed O-NCBDD microsensor exhibited a high detection sensitivity of 5.14 μA μM-1 cm-2 and a low detection limit of 25.7 nM. This finally allowed for in vivo monitoring of dopamine with an average concentration of 1.3 μM in rat brains upon 2 μL of potassium chloride stimulation, thus presenting a potential solution for the design of next-generation antifouling neural recording sensors.

Near-Infrared Fluorescence Probe with a New Recognition Moiety for the Specific Detection of Cysteine to Study the Corresponding Physiological Processes in Cells, Zebrafish, and Arabidopsis thaliana

Cysteine (Cys), as one of the biological thiols, is related to many physiological and pathological processes in humans and plants. Therefore, it is necessary to develop a sensitive and selective method for the detection and imaging of Cys in biological organisms. In this work, a novel near-infrared (NIR) fluorescent probe, Probe-Cys, was designed by connecting furancarbonyl, as a new recognition moiety, with Fluorophore-OH via the decomposition of IR-806. The use of the furan moiety is anticipated to produce more effective fluorescence quenching because of the electron-donating ability of the O atom. Probe-Cys has outstanding properties, such as a new recognition group, an emission wavelength in the infrared region at 710 nm, a linear range (0-100 μM), a low detection limit of 0.035 μM, good water solubility, excellent sensitivity, and selectivity without the interference of Hcy, GSH, and HS-. More importantly, Probe-Cys could achieve the detection of endogenous Cys by reacting with the stimulant 1,4-dimercaptothreitol (DTT) and the inhibitor N-ethylmaleimide (NEM) in HepG2 cells and zebrafish. Ultimately, it was successfully applied to obtain images of Arabidopsis thaliana, revealing that the content of Cys in the meristematic zone was higher than that in the elongation zone, which was the first time that the NIR fluorescence probe was used to obtain images of Cys in A. thaliana. The superior properties of the probe exhibit its great potential for use in biosystems to explore the physiological and pathological processes associated with Cys.

Dual-Channel/Localization Single-Molecule Fluorescence Probe for Monitoring ATP and HOCl in Early Diagnosis and Therapy of Rheumatoid Arthritis

Rheumatoid arthritis (RA), a common chronic inflammatory illness, is still incurable, reducing the sufferers' quality of life significantly. Adenosine 5'-triphosphate (ATP) and hypochlorous acid (HOCl) are key indicators in RA, but their precise mechanisms in RA pathophysiology are unknown. As a result, in order to detect ATP and HOCl simultaneously, we created two new dual-channel/localization single-molecule fluorescence probes, RhTNMB and RhFNMB. Furthermore, RhFNMB outperformed RhTNMB in terms of detection performance. ATP and HOCl produce independent fluorescence responses in the light red channel (λex = 520 nm, λem = 586 nm) and deep red channel (λex = 620 nm, λem = 688 nm), respectively, without spectral crosstalk. It should be noted that the probe RhFNMB successfully imaged ATP in mitochondria and HOCl in cells. Surprisingly, the probe RhFNMB demonstrated remarkable detection ability in the diagnosis and treatment of Pseudomonas aeruginosa-induced abdominal inflammation in mice. We continued to apply the probe RhFNMB to track ATP and HOCl in RA and discovered that ATP and HOCl concentrations were considerably greater in RA joints than in normal joints. We also confirmed the therapeutic effect of methotrexate on RA. This study is the first to achieve dual-channel imaging of ATP and HOCl, which is of great value for the early diagnosis and therapy of RA.

Microenvironment-differential Imaging of Demethylated Metabolites of Methionine for Identifying Ferroptosis Regional Preferences with Path-independent Equifinal Fluorescence Probes

We realized the microenvironment-differential Imaging of demethylated metabolites of methionine and the regional regulation of ferroptosis.

Chemically Tailored Single Atoms for Targeted and Light-Controlled Bactericidal Activity

Single-atom (SA) nanoparticles exhibit considerable potential in terms of photothermal properties for bactericidal applications. Nevertheless, the restricted efficacy of their targeted and controlled antibacterial activity has hindered their practical implementation. This study aims to overcome this obstacle by employing chemical modifications to tailor SAs, thereby achieving targeted and light-controlled antimicrobial effects. By conducting atomic-level modifications on palladium SAs using glutathione (GSH) and mercaptophenylboronic acid (MBA), their superior targeted binding capabilities toward Escherichia coli cells are demonstrated, surpassing those of SAs modified with cysteine (Cys). Moreover, these modified SAs effectively inhibit wound bacteria proliferation and promote wound healing in rats, without inducing noticeable toxicity to major organs under 808 nm laser irradiation. This study highlights the significance of chemical engineering in tailoring the antibacterial properties of SA nanoparticles, opening avenues for combating bacterial infections and advancing nanoparticle-based therapies.

High-selective two-site fluorescent probe for Cys/SO2 detection and cell imaging

A fluorescent probe has been designed using cyanine phenothiazine and 7-nitro-1,2,3-benzoxadiazole (NBD) for selective detection of Cys-SO2 components. The probe utilizes the NBD structure to achieve specificity towards Cys and employs a reaction mechanism between the double bond of cyanine and phenothiazine with SO32- to achieve selectivity towards SO2. Importantly, the NBPI phenothiazine structure incorporates a large C-O bond energy attached to NBD, effectively eliminating interference from Hcy and ensuring highly selective response to Cys. The optimized design of the probe enables excellent linearity and extremely low detection limits for Cys-SO2 components in vitro experiments. The probe NBPI allows separate detection of Cys-SO2 in the presence of both components. Furthermore, the probe NBPI demonstrated successful imaging of endogenous and exogenous Cys and SO2 in cell studies.

A metal-complex based chemosensor for the detection of riboflavin and folate

The vitamins of riboflavin and folate are necessary nutrients for maintaining the proper functioning of human body. Riboflavin and folate deficiency will cause nerve damage, leading to peripheral neuritis, depression, tongue inflammation and other diseases. The sensitive detection of riboflavin and folate keeps its significance for patients and food quality control. In this study, a quinoline-pyridine-combined chemosensor (HQ-TPE) modified by tetraphenylethene was developed. After chelating Cd2+, the chemosensor exhibited high selectivity and sensitivity for riboflavin and folate. Moreover, it can discriminate the two different vitamins through different fluorescent responses, which should arise from the different intermolecular π-π interactions between the sensor HQ-TPE and the analyte upon coordination of riboflavin or folate with Cd2+. More importantly, the chemosensor could be used in visual semi-quantitative determination of riboflavin and folate in real samples (milk and lettuce). Therefore, the sensor presented here will not only be a powerful tool for the detection of riboflavin and folate, but also provides a new template for the design of metal complex as fluorescent sensor.

A dual-responsive ratiometric indicator designed for in vivo monitoring of oxidative stress and antioxidant capacity

The imbalance between oxidative stress and antioxidant capacity is strongly associated with the development of numerous degenerative diseases, including cardiovascular diseases, diabetes, neurodegenerative diseases, and cancer. Therefore, monitoring oxidative stress and antioxidant capacity in vivo is crucial for maintaining cellular homeostasis and the stability of the organism's internal environment. Here, we present the findings of our study on DQ1, a dual-responsive indicator designed specifically for imaging H2O2 and NAD(P)H, which are critical indicators of oxidative stress and antioxidant capacity. DQ1 facilitated the colorimetric and fluorescence detection of H2O2 and NAD(P)H in two well-separated channels, exhibiting a detection limit of 1.0 μM for H2O2 and 0.21 nM for NAD(P)H, respectively. Experiments conducted on living cells and zebrafish demonstrated that DQ1 could effectively detect changes in H2O2 and NAD(P)H levels when exposed to exogenous hypoxic conditions and chemical stimuli. Furthermore, the effectiveness of the as-fabricated indicator was investigated in two distinct mouse models: evaluating H2O2 and NAD(P)H levels in myocardial cell dysfunction during acute myocardial infarction and liver tissue damage under trichloroethylene stress conditions. In vivo experiments demonstrated that the levels of the two cardiac biomarkers increase progressively with the development of myocardial infarction, eventually reaching a steady state after 7 days when the damaged cells in the infarcted region become depleted. Moreover, during 14 continuous days of exposure to trichloroethylene, the two biomarkers in liver tissue exhibited a sustained increase, indicating a significant enhancement in intracellular oxidative stress and antioxidant capacity attributed to the mouse liver's robust metabolic capacity. The aforementioned studies underscore the efficacy of DQ1 as a valuable tool for scrutinizing redox states at both the single-cell and biological tissue levels. It presents significant potential for investigating the dynamic alternations in oxidative stress and antioxidant capacity within disease models as the disease progresses, thereby facilitating a more profound comprehension of these processes across various disease models.

Copper trafficking systems in cells: insights into coordination chemistry and toxicity

Transition metal ions, such as copper, are indispensable components in the biological system. Copper ions which primarily exist in two major oxidation states Cu(I) and Cu(II) play crucial roles in various cellular processes including antioxidant defense, biosynthesis of neurotransmitters, and energy metabolism, owing to their inherent redox activity. The disturbance in copper homeostasis can contribute to the development of copper metabolism disorders, cancer, and neurodegenerative diseases, highlighting the significance of understanding the copper trafficking system in cellular environments. This review aims to offer a comprehensive overview of copper homeostatic machinery, with an emphasis on the coordination chemistry of copper transporters and trafficking proteins. While copper chaperones and the corresponding metalloenzymes are thoroughly discussed, we also explore the potential existence of low-molecular-mass metal complexes within cellular systems. Furthermore, we summarize the toxicity mechanisms originating from copper deficiency or accumulation, which include the dysregulation of oxidative stress, signaling pathways, signal transduction, and amyloidosis. This perspective review delves into the current knowledge regarding the intricate aspects of the copper trafficking system, providing valuable insights into potential treatment strategies from the standpoint of bioinorganic chemistry.

Pattern Recognition and Visual Detection of Aldehydes Using a Single ESIPT Dye

The accurate discrimination and quantification of aldehydes is a worthy objective made challenging by their similar chemical reactivities. Considering the nucleophilic reaction mechanism between an aldehyde and a primary amine, it is reasonable to vary the reaction pH to manipulate the reactivity of aldehydes and the stability of the resulting Schiff base for analytical purposes. We have designed and synthesized three benzothiazole-based fluorescent molecules (BS1-BS3) containing an amino group substituted at the ortho-, meta-, and para-positions for aldehyde sensing. It was determined that only BS1 having an amino group at the ortho-position exhibits a significant fluorescence response in the presence of formaldehyde at a particular pH, whereas BS2 and BS3 gave negligible responses, indicating that the ESIPT process in BS1 should be responsible for the changes in its fluorescence. Accordingly, a pH-mediated sensor array BS1SA was constructed by dissolving BS1 in aqueous solvents with different pH values. BS1SA was found to be reliable for the discrimination of seven different aldehydes and identification of unknown aldehyde samples. Moreover, BS1 was successfully applied to prepare a fluorescent test paper for the visual detection of formaldehyde vapor.

Recent Progress in the Rational Design of Biothiol-Responsive Fluorescent Probes

Biothiols such as cysteine, homocysteine, and glutathione play significant roles in important biological activities, and their abnormal concentrations have been found to be closely associated with certain diseases, making their detection a critical task. To this end, fluorescent probes have become increasingly popular due to their numerous advantages, including easy handling, desirable spatiotemporal resolution, high sensitivity, fast response, and favorable biocompatibility. As a result, intensive research has been conducted to create fluorescent probes for the detection and imaging of biothiols. This brief review summarizes recent advances in the field of biothiol-responsive fluorescent probes, with an emphasis on rational probe design, including the reaction mechanism, discriminating detection, reversible detection, and specific detection. Furthermore, the challenges and prospects of fluorescence probes for biothiols are also outlined.

Fluorescent probes for lighting up ferroptotic cell death: A review

Ferroptosis is a newly discovered form of regulated cellular demise, characterized by the accumulation of intracellular oxidative stress that is dependent on iron. Ferroptosis plays a crucial role not only in the development and treatment of tumors but also in the pathogenesis of neurodegenerative diseases and illnesses related to ischemia-reperfusion injury. This mode of cell death possesses distinctive properties that differentiate it from other forms of cell death, including unique morphological changes at both the cellular and subcellular levels, as well as molecular features that can be detected using specific methods. The use of fluorescent probes has become an invaluable means of detecting ferroptosis, owing to their high sensitivity, real-time in situ monitoring capabilities, and minimal damage to biological samples. This review comprehensively elucidates the physiological mechanisms underlying ferroptosis, while also detailing the development of fluorescent probes capable of detecting ferroptosis-related active species across various cellular compartments, including organelles, the nucleus, and the cell membrane. Additionally, the review explores how the dynamic changes and location of active species from different cellular compartments can influence the ignition and execution of ferroptotic cell death. Finally, we discuss the future challenges and opportunities for imaging ferroptosis. We believe that this review will not only aid in the elucidation of ferroptosis's physiological mechanisms but also facilitate the identification of novel treatment targets and means of accurately diagnosing and treating ferroptosis-related diseases.