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Electroanalysis has obtained considerable progress over the past few years, especially in the field of electrochemical sensors. Broadly speaking, electrochemical sensors include not only conventional electrochemical biosensors or non‐biosensors, but also emerging electrochemiluminescence (ECL) sensors and photoelectrochemical (PEC) sensors which are both combined with optical methods. In addition, various electrochemical sensing devices have been developed for practical purposes, such as multiplexed simultaneous detection of disease‐related biomarkers and non‐invasive body fluid monitoring. For the further performance improvement of electrochemical sensors, material is crucial. Recent years, a kind of two‐dimensional (2D) nanomaterial MXene containing transition metal carbides, nitrides and carbonitrides, with unique structural, mechanical, electronic, optical, and thermal properties, have attracted a lot of attention form analytical chemists, and widely applied in electrochemical sensors. Here, we reviewed electrochemical sensors based on MXene from Nov. 2014 (when the first work about electrochemical sensor based on MXene published) to Mar. 2021, dividing them into different types as electrochemical biosensors, electrochemical non‐biosensors, electrochemiluminescence sensors, photoelectrochemical sensors and flexible sensors. We believe this review will be of help to those who want to design or develop electrochemical sensors based on MXene, hoping new inspirations could be sparked. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel turn-on near-infrared fluorescent probe TQ-AChE was developed to detect endogenous AChE. • The probe had high selectivity and sensitivity to AChE (LOD = 0.02 U/mL) and a fast response time (30 min). • In vivo studies in mouse models validate the potential of the probe in real-time monitoring of AChE expression in liver injury. Acetylcholinesterase (AChE) is a key enzyme in the cholinergic pathway of the nervous systems, with its aberrant expression linked to various diseases. In this study, we have developed a novel Turn-On near-infrared fluorescent probe, TQ-AChE, for the sensitive and selective detection of AChE activity. Characterized by its near-infrared emission at 740 nm, TQ-AChE effectively overcomes the limitations of traditional fluorescent probes, such as short excitation wavelengths and limited tissue penetration, crucial for both in vitro and in vivo applications. The probe's low limit of detection (LOD) of 0.02 U/mL for AChE makes it highly sensitive, enabling rapid quantification of AChE activity in serum effectively. Cell imaging studies demonstrate that TQ-AChE can confirm higher AChE activity expression in normal liver cells compared to liver cancer cells. TQ-AChE can also monitor AChE fluctuations in APAP-induced acute effectively, facilitating the evaluation of the efficacy of liver detoxifying agents. Additionally, in vivo studies in mouse models validate the potential of the probe in real-time monitoring of AChE expression in liver injury. The ability of TQ-AChE to visualize AChE expression signifies its potential as a promising tool for early liver disease diagnosis and therapeutic monitoring, opening new possibilities in hepatological research and clinical diagnostics. [ABSTRACT FROM AUTHOR]

Highlights • Metal-organic framework was used as the sorbent for micro solid-phase extraction. • A semi-automated device for microextraction in packed syringe was fabricated. • The proposed method provides considerable efficiencies for extraction. • The clean-up of analytes from complex matrixes was finished in single-step. Abstract In this work, a metal-organic framework material MIL-101(Cr) was prepared and used as the sorbent for a laboratory-made semi-automated microextraction in packed syringe (MEPS). Six triazine herbicides, including desmetryn, prometon, ametryn, prometryn, atraton, and dipropetryn, that are commonly found in corn samples, were extracted and determined by the MEPS method and high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Key parameters affecting the extraction efficiencies, including type of extraction solvent, type and amount of sorbent, time of ultrasonic extraction and adsorption, and type, volume and flow rate of elution solvent, were investigated. The limits of detection (LODs, S/N = 3) and quantification (LOQs, S/N = 10) for all analytes obtained by the proposed method were in the ranges of 0.01–0.12 ng g−1 and 0.04–0.35 ng g−1, respectively, which were far lower than that of reported methods. The findings indicated that the proposed semi-automated MEPS method was easy and efficient for the extraction of triazine herbicides in corn samples. [ABSTRACT FROM AUTHOR]

Herein we report a new carbazole-benzo[e]indolium dye (CEBI) as a ratiometric fluorescent and chromogenic probe for sulfite (SO 3 2− ) detection based on intramolecular charge transfer (ICT) mechanism. Upon treatment with SO 3 2− , the probe CEBI displayed a remarkable fluorescence ratiometric response (∼560-fold fluorescenc enhancement) together with a color change from red to weak red and a large shift (135 nm) in emission wavelength. The experimentally observed changes in the spectral features of the probe upon addition of SO 3 2− were systematically studied using high resolution electrospray ionization mass spectrometry (HR-ESI–MS), proton nuclear magnetic resonance ( 1 H NMR), and time-dependent density functional theory (TDDFT) calculations. We found a linear relationship between the ratio of fluorescence intensities at 465 nm and 600 nm ( F 465 /F 600 ) and SO 3 2− concentration over the range of 0–40 μM with a detection limit of 0.025 μM. Moreover, the novel probe demonstrated fluorescence imaging of SO 3 2− in living cells and zebrafish, suggesting its potential in clinical diagnostics. [ABSTRACT FROM AUTHOR]

A water-soluble fluorescence probe (TF) derived from fluorescein has been developed. This probe can be used to detect ClO − and Cd 2+ under physiological condition based on oxidation and coordination reactions, exhibiting almost 64-fold and 4-fold fluorescence enhancement. The experimentally observed changes in the structure and electronic properties of the probe in the presence of ClO − and Cd 2+ were modeled by density functional theory (DFT) and time-dependent density functional theory (TDDFT) computational calculations. Moreover, the present probe was successfully applied to the fluorescence imaging of ClO − and Cd 2+ in living cells. [ABSTRACT FROM AUTHOR]

On the basis of fluorescence resonance energy transfer (FRET), a new rhodamine derivative (DRh) was synthesized as a ratiometric fluorescent probe for detecting Hg 2 + in water and living cells samples. The recognition properties of the probe DRh with metal ions had been investigated in H 2 O/CH 3 CN (9:1, v / v ; Tris-HCl 50 mmol L − 1 ; pH = 7.0) solution by the UV–Vis spectrophotometry and the fluorescence spectrophotometry. The results showed that the probe DRh exhibited the selective recognition of Hg 2 + . Upon the addition of Hg 2 + , the spirolactam ring of probe DRh was opened. The 1:1 stoichiometric structure between DRh and Hg 2 + were supported by Job's plot, MS and DFT theoretical calculations. The linearly fluorescence intensity ratio ( I 582 / I 538 ) is proportional to the concentration of Hg 2 + in the range 0–30 μmol L − 1 . The limit of detection (LOD) of Hg 2 + is 0.008 μmol L − 1 (base on S/N = 3). The present probe was applied to the determination of Hg 2 + in neutral water samples and gave recoveries ranging from 104.5 to 107.9%. Furthermore, the fluorescent probe also can be applied as a bioimaging reagent for Hg 2 + detection in HeLa cells. [ABSTRACT FROM AUTHOR]

Based on fluorescein, a novel water-soluble and reversible fluorescent probe (Flu-Py) was designed and synthesized for the sequentially “ON–OFF–ON” fluorescent detection of Al 3+ and F − in concentration range of 0–10 μmol L −1 and 0–30 μmol L −1 , respectively, with high sensitivity and excellent selectivity. The detection limits for Al 3+ and F − were 0.092 μmol L −1 and 0.112 μmol L −1 , respectively. The binding mode and sensing mechanism of Flu-Py with Al 3+ was verified by density functional theory (DFT) and time dependent density functional theory (TDDFT) calculation. The “ON-OFF–ON” fluorescent property of Flu-Py upon the addition of Al 3+ and F − was utilized for the imaging of living cells. [ABSTRACT FROM AUTHOR]

A trivalent chromium (Cr 3 + ) fluorescence probe (RhC) was designed and synthesized via Schiff base reaction based on rhodamine–crown ether conjugate. This probe displayed a favorable selectivity for Cr 3 + over a range of other common metal ions in DMF/H 2 O (3:7, v / v ; PBS buffer 50 mmol L − 1 ; pH = 6.8) solution, leading to prominent fluorescence “OFF–ON” switching of the rhodamine fluorophore. The limit of detection was calculated to be 1.5 μmol L − 1 (S/N = 3). The binding ratio of RhC–Cr 3 + complex was determined to be 1:2 according to the Job's plot and HR-MS. The probe was successfully applied to examination of Cr 3 + in drinking water spiked samples. The average recoveries ranged from 104.9% to 106.9% at spiked concentration level of 10.00 μmol L − 1 , and the obtained results were consistent with those obtained using atomic absorption spectrometry (AAS). Moreover, bioimaging experiments showed that RhC can sense the Cr 3 + in living cells with a fluorescence enhancement signal. [ABSTRACT FROM AUTHOR]

A reversible off-on-type probe for pH sensing with fluorescence and surface-enhanced Raman scattering (SERS) dual-signal output, Rhodamine–phenanthroline (RGP), was designed and synthesized from Rhodamine 6G and 1,10-phenanthroline. Due to the molecular structure transformation between spirocyclic and ring-open forms, RGP exhibits varying fluorescence and SERS activities at different pH levels. The values of acidity constants ( pK a ) and fluorescence quantum yield ( Φ ) of RGP were 2.43 (±0.14) and 0.48, respectively. The fluorescence change of RGP was reversible and took place mainly within the pH range from 1.0 to 4.0. The SERS signals of RGP could be stable more than 3 h under room temperature and with little loss of efficiency after the pH of the sample solution was switched between 3.29 and 6.09 for 5 times. Most of the common inorganic ions and polycyclic aromatic hydrocarbons (PAHs) in water samples have little influence on the analytical performance of the probe. The present probe is simple and easy-to-use for the pH sensing in acidic media. [ABSTRACT FROM AUTHOR]

A selective and ultrasensitive surface-enhanced Raman spectroscopy (SERS) method was developed for the determination of formaldehyde (HCHO) in environmental waters and food samples. It is based on derivatization of HCHO with 4-amino-5-hydrazino-3-mercapto-1,2,4-triazole (AHMT) with HCHO. One of the products of the derivative reaction, 6-mercapto-5-triazolo[4,3-b]-s-tetrazine (MTT), can be quantified by SERS at 832 cm using silver nanoparticles (AgNPs) as substrates. The incubation time for derivatization, the volume of reagents and the mixing times were optimized. The peak areas of the SERS are linearly related to the concentration of HCHO in the 1 − 1,000 μg L range, the limit of detection is 0.15 μg L, and the limit of quantification is 0.45 μg L. Recoveries obtained by analyzing two spiked samples of environmental water and two spiked food samples were in the range between 91.0 and 108.7 %. There is no significant difference between the results obtained by the present method and the liquid chromatographic method (Chinese industrial standard method, SN/T 1547-2011). [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

We have developed a SERS method for the determination of o-phenylenediamine (OPD) in water. It is based on the chemical cyclization reaction of OPD with nitrite in acidic medium. Benzotriazole (BTAH), one of the products of the reaction, can be determined by SERS with high sensitivity when using silver nanoparticles decorated with α-cyclodextrin (α-CD-AgNPs) as a substrate. The acidity of the medium, nitrite concentration, reaction time and mixing time for solutions of analytes and SERS substrates were optimized. The enhancement factors of the optimal SERS substrates (even if stored for a few months) range from 2.17 × 10 to 2.52 × 10 when utilizing the SERS peak at 1,602 cm. Other figures of merit include (a) a linear analytical range from 0.10 to 1.0 μmol L, (b) a detection limit of 30 nmol L, and (c) a quantification limit at 100 nmol L. The high selectivity for OPD was confirmed by studies on the potentially interfering species m- and p-phenylenediamine, aniline, and 1-naphthylamine. Recoveries of OPD from spiked real water samples ranged from 97.8 to 104.5 %, with relative standard deviations of less than 4 %. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

We have developed a surface-enhanced Raman scattering (SERS) probe for the determination of mercury(II) using methimazole-functionalized and cyclodextrin-coated silver nanoparticles (AgNPs). These AgNPs in pH 10 solution containing sodium chloride exhibit strong SERS at 502 cm. Its intensity strongly decreases in the presence of Hg(II). This effect serves as the basis for a new method for the rapid, fast and selective determination of trace Hg(II). The analytical range is from 0.50 μg L to 150 μg L, and the limit of detection is 0.10 μg L. The influence of 11 metal ions commonly encountered in environmental water samples was found to be quite small. The method was applied to the determination of Hg(II) in spiked water samples and gave recoveries ranging from 98.5 to 105.2 % and with relative standard deviations of <3.5 % ( n = 5). The total analysis time is <10 min for a single sample. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

We have synthesized silver nanoparticles (AgNPs) decorated with α-cyclodextrin (CD) by using the traditional silver mirror reaction in the presence of CD. The CD-AgNPs were used as substrate in surface-enhanced Raman spectroscopy (SERS) for determining melamine. The intensity of the Raman band of melamine at 704 cm was used to determine melamine in milk and milk powder. The use of CD-AgNPs as the SERS substrate rather than classical silver nanoparticles makes the method more sensitive in giving an enhancement by a factor of up to ~ 10 in scattering efficiency. The effects of the volume of solutions (of CD-AgNPs, NaCl, NaOH, melamine) and of mixing time were optimized. The standard addition method was employed for quantitative analysis. The correlation coefficient of the calibration plot is 0.9995, and the limit of detection is 3.0 μg L. The method was successfully applied to the determination of melamine in milk and milk powder, with relative standard deviations of <10 % and recoveries between 89 and 104 %. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Carcinoembryonic antigen (CEA) is an important cancer marker that plays a significant role in achieving low-cost, rapid and highly sensitive clinical detection. In this work, we developed a disposable electrochemiluminescence (ECL) sensor chip based on a screen-printed electrode (SPE) for detecting CEA via ECL technology. An amino-modified Ti3C2 MXene was used as a carrier to successfully prepare a highly efficient ECL probe AuNPs-Ru-Arg@NH2-Ti3C2-MXene by loading with AuNPs-Arg through covalent links and modifying with a ruthenium complex. Upon the addition of CEA, the ECL signal decreased significantly with the increase of CEA, due to the formation of immune complexes at the interface of the electrode. The sensing chip was used to detect CEA in an aqueous solution and found to have a detection limit of 1.5 pg mL−1. The chip was used to determine CEA in the serum of healthy humans and cancer patients, and the results were consistent with those obtained using ELISA. The disposable ECL sensor chip has many advantages including convenience, rapid detection, low cost and easy mass production; thus it has great application potential in clinical cancer diagnosis. [ABSTRACT FROM AUTHOR]

Cellulose paper was coated with the metal-organic framework MIL-101(Cr) in a chitosan matrix and utilized for thin-film microextraction (TFME). The coated paper possesses excellent extraction efficiency for the triazine herbicides atraton, desmetryn, secbumeton, prometon, ametryn, dipropetryn, and dimethametryn. High-performance liquid chromatography-tandem mass spectrometry was applied to quantify target analytes. The effects of mass ratio of MIL-101(Cr) to chitosan, sample pH value, time of adsorption and desorption, and type and volume of desorption solvent on extraction efficiency were optimized. Under the optimal conditions, the method has limits of detection between 1.5 and 22 ng·L−1. The recoveries of triazines from spiked tap water, drinking water, lake water and river water range from 77.0 to 125.3%, with relative standard deviations of <17.4%. [ABSTRACT FROM AUTHOR]

Ascorbic acid (AA) is an essential vitamin in humans, and numerous AA detection studies have been conducted. Most quantum dots (QDs)-based approaches depend on redox reactions involving AA, and they require the introduction of an intermediate (e.g., metal ions, OPD, TMB) or the assembly of fluorescent substances with nanosheets (such as MnO 2) that can be degraded by AA. These methods are complex, unstable, and are susceptible to interferences. To address these problems, a core-shell fluorescence probe was developed for turn-on sensing of AA. The transition metal oxide shell FeOOH was generated around the surface of CuInZnS QDs to quench the fluorescence. In the presence of AA, the FeOOH shell was decomposed into Fe2+ and the fluorescence of QDs was recovered. Using a physical shell, the obtained nanocomposite realized direct AA detection, avoiding the effects of interfering substances caused by QDs exposure. Moreover, our probe showed great potential in point-of-care tests and was readily adapted for use as a smartphone-assisted paper sensor. [Display omitted] • A core-shell fluorescence probe CuInZnS QDs@FeOOH was developed for turn-on sensing of ascorbic acid (AA). • The probe can realize direct and convenient AA detection without intermediate intervention and complicated processing. • By building a physical shell, the probe can avoid the effect of interfering substances causing by QDs exposure. • A smartphone-assisted paper sensor was fabricated and exhibited great potential in point-of-care test. [ABSTRACT FROM AUTHOR]

Glutathione-capped water-soluble CuInS/ZnS quantum dots (QDs) were prepared by a microwave-assisted method. Their fluorescence, with excitation/emission peaks at 380/570 nm, is found to be quenched by hydrogen peroxide (H2O2) that is produced by the uricase catalyzed oxidation of uric acid (UA) and oxygen. The findings are used in a quenchometric method for the determination of UA. The effects of different ligands on the QDs, of pH value, buffers, enzyme ratio and reaction time were optimized. The detection limit for UA is 50 nM which is lower than other QD-based method, and the detection ranges extends from 0.25-4.0 μM. The assay is simple and sensitive, and no further modification of the QDs is required.ᅟ [ABSTRACT FROM AUTHOR]

This study presents a novel, eco-friendly composite adsorbent material designed for the magnetic solid-phase extraction of diamide insecticides from vegetable samples. The membrane, denoted as Fe-MMm, was incorporated with a cellulose framework embedded with Metal-Organic Frameworks (MOFs) and Multi-Walled Carbon Nanotubes (MWCNTs) magnetized with Fe 3 O 4. This innovative material streamlined the conventional solid-phase extraction process, simplifying the sample pre-treatment. By combining it with liquid chromatography tandem mass spectrometry (LC-MS/MS), the method achieves significantly enhanced extraction efficiency through systematic optimization of experimental parameters, including adsorbent selection, pH, ionic strength, adsorption time, and elution time. The method had a wide linear range of 0.1–1000 ng/mL and an exceptionally low detection limit ranging from 0.023 to 0.035 ng/mL. The successful identification of diamide insecticides in vegetable samples underscores the potential of Fe-MMm as a robust material for sample pretreatment in analytical applications. [Display omitted] • The MOF and MWCNTs@Fe 3 O 4 are embedded in the skeleton of MFC. • A solid-phase extraction method based on Fe-MMms was proposed and detected using LC-MS/MS. • Fe-MMm demonstrates excellent reusability in solid-phase extraction, with minimal performance changes after 10 uses. • The method exhibits extremely high sensitivity and a wide linear range, with an exceptionally low detection limit ranging from 0.023 to 0.035 ng/mL. [ABSTRACT FROM AUTHOR]

In the present study, a novel ratiometric fluorescence probe based on dual-emitting Mn-doped ZnS quantum dots (Mn:ZnS QDs) was established for detection of Pb2+ and methyl parathion (MP). The dual-emitting Mn:ZnS QDs was aqueous synthesised in one pot and played as a ratiometric fluorescence probe for the detection of Pb2+ with high sensitivity. The fluorescence intensity ratio (F 450nm /F 585nm) of the probe against the concentration of Pb2+ showed a good linear relationship from 10 nM to 60 nM with a detection limit of 0.5 nM. Furthermore, the Mn:ZnS QDs/Pb2+ system was established as a turn-on fluorescence sensing system to quantitative measure the MP concentration. The fluorescence intensity at 450 nm exhibited a good linear relationship in the MP concentration range from 0.19 to 0.95 μM with a detection limit of about 0.02 μM. It also had a satisfying performance in fruit and environmental water samples. Therefore, the prepared Mn:ZnS QDs-based sensor has been established as a ratiometric fluorescence probe and turn-on method for quantitative detection of lead ion and MP, respectively. Image 1 • A novel ratiometric fluorescence probe based on dual-emitting Mn-doped ZnS quantum dots (F 450nm /F 585nm) was established for Pb2+ detection. • The organophosphorus hydrolysate can "turn-on" the fluorescence sensor. • The proposed "turn-on" fluorescence sensor system was applied to quantitative analysis of methyl parathion with a low detection limit of 0.02 μM. • The "turn-on" fluorescence sensor strategy is selective to P–S bond organophosphorus pesticides. [ABSTRACT FROM AUTHOR]

Abstract Typically, sialic acids (SA) with a nine-carbon backbone are found at the glycan chain termini on the cell membranes, which play crucial roles in various physiological and pathological processes. The expression level of SA in the blood serum has been reported to correlate with various disease states among cancer. In this study, a novel approach for preparing fluorescent boronic-acid-modified carbon dots (C-dots) for the detection of SA was developed. The functionalized C-dots were synthesized by a facile, one-step hydrothermal method using 3-pyridineboronic acid as the sole carbon source. The added SA selectively recognized the C-dots, leading to the fluorescence quenching of the C-dots in a linear range of 80–4000 μM with a detection limit of 54 μM. The as-developed boronic-acid nanoprobe was successfully applied for the detection of SA in human serum samples with satisfactory results. In addition, this method afforded results within 4 min. Compared to other methods, this new proposed approach was simpler and exhibited excellent sensitivity and selectivity, demonstrating immense potential as an alternative for SA detection. Graphical abstract fx1 Highlights • In this study, a simple, sensitive nonenzymatic strategy for SA detection with carbon dots. • The sensor exhibited high selectivity and sensitivity. • This method is applied to detect sialic acid in real samples with satisfactory recoveries. • This method does not require any complicated modifications and expensive instrumentation. [ABSTRACT FROM AUTHOR]

Abstract A novel fluorescence detection method based on competitive immunoassay and magnetic bioseparation technique was developed and applied to the determination of pig immunoglobulin G (IgG) in serum samples. Core-shell structured Fe 3 O 4 @SiO 2 nanoparticles were synthesized by chemical coprecipitation, followed by functionalization with amino groups and immobilization of pig IgG antibodies. The synthesized Fe 3 O 4 @SiO 2 -antibody nanoparticles were employed as the probe for the competitive immune recognition of the target antigens in samples and the antigens labeled with fluorescein isothiocyanate (FITC). After the magnetic separation of probes binding with these two types of antigens, fluorescence of the free FITC-labeled antigens was measured for the quantification of the target antigens, since the ratio of the FITC-labeled antigens in supernatant before and after the competitive immune recognition depends on the amount of the target antigens in sample, due to the competitive nature of the binding of the antibody for these two types of antigens. Under the optimal conditions, a linear relationship was obtained between the change of fluorescence intensity and the concentration of pig IgG in a range from 0.75 to 23.50 µg L−1, with a detection limit (LOD) of 0.031 µg L−1. With the facile-prepared probes, this fluorescence competitive method can provide a rapid, specific and highly sensitive immunoassay protocol for the determination of target proteins in complex matrix samples. Graphical abstract fx1 Highlights • The analysis was simplified through competitive immunoreactions and magnetic bioseparation. • Good sensitivity and selectivity were obtained by taking advantage of fluorescence immunoassay. • The results of analyzing serum samples indicate its promising potential in clinical diagnosis. [ABSTRACT FROM AUTHOR]

Alkaline phosphatase (ALP) is an essential enzyme in various tissues, which has been reported to be extensively involved in various physiological and pathological processes. Fluorescent probe assays carried out in vivo are desirable for monitoring the ALP activity. In this study, a novel red-light fluorescent DHP probe, which exhibited good selectivity and high sensitivity, for monitoring the ALP activity in real time was described. The DHP probe exhibited good water solubility, and the detection limit of ALP was determined as 0.031 U/L; this value is almost less than those of the other probes reported previously. The probe exhibited high selectivity, which will not interfere with various enzymes and amino acids. Moreover, the sensing and luminescence mechanisms of ALP to DHP was investigated by density functional theory (DFT) and time-dependent DFT. Furthermore, the DHP probe was applied for the detection of endogenous ALP in BEL-7402 cells, and the fluctuation of the ALP levels in BEL-7402 and HEK 293 T cells was successfully tracked by fluorescence microscopy. [ABSTRACT FROM AUTHOR]

Early diagnosis of chronic, critical diseases improves clinical outcomes, and biomarkers play an important role as an indicator of severity or presence of a disease. Alkaline phosphatase (ALP) is one such vital biomarker in the diagnosis of several diseases. Herein we introduce a facile, sensitive fluorescent assay, based on the inner filter effect (IFE), for ALP activity determination in serum and in living cells. It is well known that the key to maximize the sensitivity of an IFE-based fluorescence assays is to broaden the overlap between the absorption of an absorber and the excitation/emission of a fluorophore. We employed CuInS/ZnS quantum dots (CIS/ZnS QDs) and p -nitrophenylphosphate (PNPP) as the fluorescent indicator and the substrate, respectively, for ALP activity assessment. Due to the CIS/ZnS QDs have an efficient excitation at 405 nm, meanwhile with a large Stokes shift emission at 588 nm, p -nitrophenol (PNP) with absorption peak at 405 nm, the hydrolyzed produce of PNPP and ALP, can act as a competitive absorber to absorb the excitation light of CIS/ZnS QDs, resulting in noticeable quenching of CIS/ZnS QDs. The proposed sensor detects ALP activity in human serum samples (sample consumption: 20 μL) with detection limit of 0.01 U L -1 . Excellent biocompatibility of CIS/ZnS QDs enables the sensor to monitor endogenous ALP in living cells. Furthermore, because the surface modification or the linking between the receptor and the fluorophore is no longer required, this fluorescent sensing system has the potential to simplify ALP clinical measurement, thereby improving diagnostics of relevant diseases. [ABSTRACT FROM AUTHOR]

A novel surface plasmon resonance (SPR) biosensor based on hollow gold nanospheres (HGNPs) and an improved sandwich assay was developed to detect rabbit IgG. The electromagnetic coupling between the HGNPs and Au film, and the notable plasmonic fields spread over the inner and outer surfaces of HGNPs, led to the considerable amplification of the SPR signal. Polydopamine-Ag@Fe 3 O 4 /reduced graphene oxide (PDA-Ag@Fe 3 O 4 /rGO) was introduced to bind detection antibody (Ab 2 ) to form the improved sandwich structure. Ag nanoparticles were excited to produce SPR and their hot electrons were doped on graphene thin films, which amplified the response of biomolecules. Magnetic nanoparticles (Fe 3 O 4 ) simplified the collection of Ab 2 -PDA-Ag@Fe 3 O 4 /rGO. An external layer of polydopamine (PDA) permitted the efficient immobilization of Ab 2 without activation via abundant functional groups and protected the nanoparticles from etching or agglomeration. In addition, because of its large mass, Ab 2 -PDA-Ag@Fe 3 O 4 /rGO also played a key role in the further amplification of the SPR response signals. This novel SPR biosensor exhibited an effective response to the rabbit IgG at the different concentrations ranging from 0.019 to 40.00 μg mL −1 . This value is 132 times lower than that observed for a traditional SPR biosensor based on Au-3-mercaptopropionic acid and 8 times lower than that obtained from an Ab 2 sandwich assay, which indicates that the SPR sensor has high sensitivity. In addition, the designed biosensor showed satisfactory recoveries to detect the rabbit IgG spiked in serum samples. Therefore, the novel SPR biosensor with high sensitivity and acceptable recovery has potential for practical applications. [ABSTRACT FROM AUTHOR]

Herein, we report a novel Schiff base “turn-on” fluorescent and chromogenic probe N′-(3-(benzo[d]thiazol-2-yl)-2-hydroxybenzylidene)-4-(dimethylamino)-benzohydrazide (BHDB) for CN − detection under physiological pH, based on nucleophilic reaction of imine ( CH N ) and CN − , exhibiting almost 66-fold fluorescence increase and a remarkable color change from colorless to yellow. The experimentally observed changes in the spectral properties of the probe upon addition of CN − were systematically studied using high resolution electrospray ionization mass spectrometry (HR-ESI-MS), proton nuclear magnetic resonance ( 1 H-NMR), and time-dependent density functional theory (TDDFT) calculations. Using the fluorescence spectra changes, we found a detection limit for CN − of 0.15 μmol L −1 , far lower than the maximum permissive level of CN − (1.9 μmol L −1 ) in drinking water recommended by World Health Organization (WHO). Moreover, the novel probe demonstrated fluorescence imaging of CN − in living cells and zebrafish, suggesting its potential in clinical diagnostics. [ABSTRACT FROM AUTHOR]

Oral health is an essential part of overall health. Matrix metalloproteinase-2 (MMP-2) is a potential biomarker for diseases. The ability to accurately detect MMP-2 in vivo and in vitro is of great importance for the early diagnosis and prognosis, as well as the treatment evaluation, of oral diseases. In this study, cyanine 3 (Cy3) polypeptide containing the specific peptide substrate (PLGVR) of MMP-2 was modified onto SiO 2 -coated upconversion nanoparticles to fabricate a fluorescence resonance energy transfer (FRET)-based ratiometric fluorescent nanoplatform (UCNPs@SiO 2 @Cy3-pep). The green upconversion luminescence of UCNPs@SiO 2 is quenched by Cy3, while its red upconversion luminescence is undisturbed. After Cy3 is cleaved at the PLGVR peptide by MMP-2, it is detached from the surface of UCNPs@SiO 2 , resulting in the recovery of green luminescence. Based on this principle, we applied UCNPs@SiO 2 @Cy3-pep to detect MMP-2 activity in different oral disease samples and models. We found that the level of MMP-2 in saliva of patients with oral cancer was 10 times higher than that of healthy individuals. In addition, the MMP-2 level in patients with periodontitis and severe dental caries also increased to varying degrees compared with that in healthy patients. Finally, in vitro and in vivo imaging experiments revealed that the nanoplatform was effective in monitoring MMP-2 level. Together, the developed nanoplatform can be an ideal tool for medical diagnosis of MMP-2-related diseases. [Display omitted] • The developed nanoplatform can be an ideal tool for medical diagnosis of MMP-2 related diseases. • The nanoplatform provides a detection limit of MMP-2 as low as 0.2 ng/mL. • The nanoplatform will facilitate the progress of revealing the biological roles of MMP-2 in oral diseases. • The constructed nanoprobe is suitable for real-time monitoring of MMP-2 in vivo and in vitro. [ABSTRACT FROM AUTHOR]

Aminopeptidase N (APN) plays an important role in promoting the circulation of amino acids and influences many important physiological functions of organisms. Monitoring of APN level is of great value for the early clinical diagnosis and prognosis of diseases and certain cancers. In this study, we designed a ratiometric APN fluorescent chemosensor NB-APN by using Nile blue derivative as a fluorophore and alanyl as a recognition unit. After APN was recognized by alanyl of NB-APN, the NB previously blocked by the alanyl group was released, causing the inverse evolution trend of fluorescence intensitis of signal peaks at 675 nm and 610 nm. The ratiometric signal sensitively responded to the concentration of APN, and the detection limit was as low as 15 pg/mL. This chemosensor was successfuly applied for quantitative detection of APN in urine samples. Moreover, the chemosensor realized ratiometric fluorescence imaging of APN in in vitro and in vivo , and demonstrated the potential value of APN in the diagnosis and treatment of liver diseases in a drug-induced liver injury model. Therefore, the proposed chemosensor can potentially be applied in diagnosis of APN-related diseases. [Display omitted] • We designed a ratiometric APN fluorescent chemosensor NB-APN by using Nile blue (NB) derivative. • The detection limit was as low as 15 pg/mL. • The chemosensor realized ratiometric fluorescence imaging of APN in in vitro and in vivo. • The proposed chemosensor can potentially be applied in diagnosis of APN-related diseases. [ABSTRACT FROM AUTHOR]

A new rhodamine derivative (RhS) with a recognition capability for Cu 2+ was synthesized and employed as a reversible fluorescent probe for Cu 2+ in drinking water and living cells. The spirolactam ring-opening of probe RhS induced by Cu 2+ lead to a highly selective fluorescence “turn-on” response toward Cu 2+ over other metal ions with micromolar sensitivity. The 1:1 stoichiometric structure between RhS and Cu 2+ were supported by Job's plot, MS and DFT theoretical calculations. The analytical results obtained by UV–vis and fluorescence spectrophotometry show that the linear range and the limit of detection (LOD) of the present probe for Cu 2+ are 0.50–20.00 and 0.11 μmol L −1 , respectively. The present probe was applied to the detection of Cu 2+ in drinking water with the recoveries ranging from 100.4 to 101.2%, and the fluorescence imaging for living HeLa cells. [ABSTRACT FROM AUTHOR]

A new high-sensitivity surface plasmon resonance (SPR) biosensor based on biofunctional gold nanostars (AuNSs) and carboxyl-functionalized graphene oxide (cGO) sheets was described. Compared with spherical gold nanoparticles (AuNPs), the anisotropic structure of AuNSs, which concentrates the electric charge density on its sharp tips, could enhance the local electromagnetic field and the electronic coupling effect significantly. cGO was obtained by a diazonium reaction of graphene oxide (GO) with 4-aminobenzoic acid. Compared with GO, cGO could immobilize more antibodies due to the abundant carboxylic groups on its surface. Testing results show that there are fairly large improvements in the analytical performance of the SPR biosensor using cGO/AuNSs-antigen conjugate, and the detection limit of the proposed biosensor is 0.0375 μg mL −1 , which is 32 times lower than that of graphene oxide-based biosensor. [ABSTRACT FROM AUTHOR]

Autoimmune thyroid diseases (AITD) often interfere with early detection due to asymptomatic symptoms and normal thyroid function in routine tests. Developing early diagnostic tools is crucial for timely and accurate treatment, potentially reducing complications and improving patient outcomes. In this study, we developed Ox-NE, a novel fluorescent probe designed for the specific detection and quantification of neutrophil elastase (NE), a key biomarker of inflammation. Unlike the traditional probes, Ox-NE utilizes a unique mechanism that minimizes background fluorescence and enhances photostability, offering rapid, non-invasive, and apparent diagnostic capabilities. Ox-NE had a low limit of detection (LOD) of 1.54 μg/mL and exhibited high sensitivity and specificity with strong anti-interference properties. Through in vitro experiments, Ox-NE could accurately detect elevated NE levels in the serum of thyroiditis patients. Additionally, it could differentiate between normal thyroid cells, inflamed thyroid cells, and thyroid cancer cells. It also effectively facilitated the screening of sivelestat, a therapeutic agent for thyroiditis. Successful fluorescence imaging in mouse models further confirmed the potential of Ox-NE in advancing thyroid disease diagnostics. [Display omitted] • Ox-NE is the first non-conjugated organic probe to detect autoimmune thyroiditis, effectively reducing high background signals. • Ox-NE could effectively distinguish between thyroid inflammation and thyroid cancer. • NE shows potential as a clinical biomarker of serum in thyroid diseases, with Ox-NTR as a promising diagnostic imaging tool. [ABSTRACT FROM AUTHOR]

Due to the detrimental effects of various harmful substances—such as carcinogens, drug toxicity, and environmental pollutants—on the liver, which can trigger or exacerbate conditions like hepatocellular carcinoma (HCC), drug-induced liver injury (DILI), and non-alcoholic fatty liver disease (NAFLD), accurate detection and monitoring of these diseases are crucial for effective treatment. Carboxylesterase 2 (CES2) is primarily found in the liver and, as a potential biomarker, its accurate detection can enhance the early diagnosis and treatment efficacy of liver diseases. Traditional fluorescence probes for CES2 detection suffer from non-specific recognition groups, leading to poor targeting specificity. To address this limitation, we propose a novel CES2-responsive fluorescent probe utilizing cholic acid (CA) as a recognition group. The probe, LAN-CA, was synthesized by esterifying CA with a near-infrared fluorophore, LAN-OH. This novel fluorescent probe leverages the unique affinity of CA for hepatocytes, ensuring that LAN-CA remains and accumulates specifically within the hepatoenteric circulation. In vitro experiments showed that the probe exhibits superior optical performance compared to traditional benzoate-based probe (LAN-PH), with a detection limit of 0.015 μg/mL. Examination of 56 common biological interferents demonstrated that using CA as a recognition group offers high selectivity. Cell experiments confirmed that LAN-CA is an effective tool for monitoring endogenous CES2 in live cells. Comprehensive evaluations of fluorescence imaging in various mouse models of liver diseases, such as HCC, DILI, and NAFLD, demonstrated that LAN-CA provides exceptional imaging accuracy and therapeutic monitoring capabilities. In conclusion, this probe not only can be a promising tool for accurate liver disease diagnosis, but also can provide valuable insights into treatment efficacy. [Display omitted] • Probe LAN-CA selected cholic acid as a novel recognition group for CES2. • Cholic acid is not only a recognition group, but also has a good hepatoenteric targeting ability. • Probe LAN-CA effectively imaged hyperlipidemic cells and monitored their recovery process. • LAN-CA was successfully used for diagnosing hepatoenteric diseases and monitoring NAFLD drug therapy. [ABSTRACT FROM AUTHOR]

Near-infrared (NIR) fluorescent probes have excellent properties such as fast imaging speed, non-invasive, good stability and low background interference, and have great application potential in biological imaging and surgical guidance. At present, the study of fluorescent probes with long time imaging has attracted extensive attention to guide surgery, while some issues need to be considered, such as toxicity, long tissue residence time and long time for metabolism. Meanwhile, fluorescent probes with rapid metabolism tend to decay fast. Therefore, fluorescent probes need to be continuously designed and synthesized to achieve a balance of performance between suitable imaging time and reasonable metabolic rate. To this end, we design a NIR fluorescence probe that can not only complete the needs of in vivo or cell imaging in a reasonable time, but also can rapidly metabolize and shorten its residence time in the body. The synthesis of a rapidly metabolizable NIR fluorescent probe Kang-CES2 were based on isophorone for enzyme-activated imaging anaplastic thyroid cancer (ATC) in vivo. Kang-CES2 has demonstrated excellent imaging capabilities in vivo and potentiality as a spray and biopsies tool. Meanwhile, the results of intratumoral injection in mice showed that Kang-CES2 can quickly distinguish between normal and ATC tissues and continue to emit NIR light until the end of surgery. The results of tail vein injection of mice showed that Kang-CES2 can rapidly metabolize in the body within 33 minutes. We believe Kang-CES2 has the potential to be a powerful fluorescent tool capable of guiding ATC surgical resection with rapid metabolism. • Kang-CES2 achieve a balance of performance between reasonable imaging time and rapid metabolic rate. • Kang-CES2 is based on isophorone synthesis, which is simple and fast. • Kang-CES2 is a highly specific enzyme-activated probe that can specifically identify CES2 in vitro and in vivo. • Kang-CES2 has the ability to be used as a spray tool and a biopsies tool. [ABSTRACT FROM AUTHOR]

The toxicity of organophosphorus pesticides (OPs) can catastrophically cause liver cell damage and inhibit the catalytic activity of cholinesterase. We designed and synthesized a near-infrared fluorescent probe HP-LZB with large Stokes shift which can specifically identify and detect butyrylcholinesterase (BChE) and visually explore the interaction between OPs and endogenous BChE in living cells. Fluorescence was turned on when HP-LZB was hydrolyzed into HP-LZ in the presence of BChE, and OPs could inhibit BChE's activity resulting in a decrease of fluorescence. Six OPs including three oxon pesticides (paraoxon, chlorpyrifos oxon and diazoxon) and their corresponding thion pesticides (parathion, chlorpyrifos and diazinon) were investigated. Both in vitro and cell experiments indicated that only oxon pesticides could inhibit BChE's activity. The limits of detection (LODs) of paraoxon, chlorpyrifos oxon and diazoxon were as low as 0.295, 0.007 and 0.011 ng mL−1 respectively and the recovery of OPs residue in vegetable samples was satisfactory. Thion pesticides themselves could hardly inhibit the activity of BChE and are only toxic when they are converted to their corresponding oxon form in the metabolic process. However, in this work, thion pesticides were found not be oxidized into their oxon forms in living HepG2 cells due to the lack of cytochrome P450 in hepatoma HepG2 cell lines. Therefore, this probe has great application potential in effectively monitoring OPs in real plant samples and visually exploring the interaction between OPs and BChE in living cells. [Display omitted] • HP-LZB is a near-infrared probe that can specifically recognize and detect BChE. • HP-LZB was used to detect OPs in vitro and in living cells. • Oxon OPs inhibit BChE's activity, resulting in a decrease of cell fluorescence. • Thion pesticides were found not be oxidized into their oxon forms in HepG2 cells. • The LODs of chlorpyrifos oxon and diazoxon were as low as 0.007 and 0.011 ng mL−1. [ABSTRACT FROM AUTHOR]

A rapid, simple, and sensitive method for the determination of Rhodamine B in chili powder was established based on surface-enhanced Raman spectroscopy using citrate-coated silver nanoparticles as the substrate. This substrate was found to produce enhancement factors of 1.6 × 107 at 625 per centimeter. A portable Raman spectrometer was used allowing on-site measurements. The effects of the volume of silver nanoparticle solution, the volume of hydrochloric acid, the volume of Rhodamine B, and the mixing time were optimized. The linear dynamic range was from 0.2 to 20.0 micrograms per liter and the limit of detection was 0.08 microgram per liter. The method was applied to the determination of Rhodamine B in chili powder, with recoveries between 81.42 and 97.22 percent, and relative standard deviation values lower than 4.84 percent. [ABSTRACT FROM AUTHOR]

Non-alcoholic fatty liver disease (NAFLD) now affects more than one quarter of the global population and becomes a heavy public health burden. However, the underlying mechanism for the pathogenesis of NAFLD is still not clear. Carboxylesterase 2 (CES2), highly abundant in the liver and intestine, plays an important role in endogenous lipid metabolism and lipolysis. So far, the literatures for the role of CES2 in the development of NAFLD are still limited. In this study, we designed and synthesized a near-infrared fluorescent probe (HP-LZ-CES2) which can be specifically recognized and hydrolyzed by CES2, releasing a benzoate residue and a fluorophore (HP-LZ) with good fluorescence signal. With this probe, CES2 levels can be quantitatively measured in vitro and qualitatively visualized in living cells and mice. The probe has the advantages of large Stokes shift, high detection sensitivity and good selectivity. Further, the CES2 expression levels were visually investigated in both high-fat cells as the in vitro model for NAFLD and high-fat diet fed mouse as the in vivo model for NAFLD. The cell imaging experiments indicated a reduction of fluorescence signal in high-fat hepatic cells. The in vivo experiments showed an obvious reduction of fluorescence in the liver of NAFLD mouse model, which is consistent with the hepatic cell experiments. In contrast, an enhancement of fluorescence was observed in the intestine of NAFLD mouse model. As a result, the NAFLD mouse model can be visually distinguished from the normal chow mouse by vision. Therefore, the proposed probe can be an auxiliary tool for the diagnosis of NAFLD and a visual tool for understanding CES2's role in the development of NAFLD. [Display omitted] • HP-LZ-CES2 is a near-infrared probe that specifically recognizes and detects CES2. • A reduction of CES2 was found in high-fat hepatic cells and NAFLD mouse liver. • The probe can distinguish NAFLD mouse model from mouse with normal diet. [ABSTRACT FROM AUTHOR]

Atherosclerosis (AS) is a common disease associated with cholesterol metabolism. Cholesterol esterase (CHE), which is found primarily in the liver, intestines, adipose tissue, and skin, plays a crucial role in cholesterol metabolism; thus, it is a potential biomarker for the early diagnosis and therapeutic monitoring of AS. Traditional fluorescent probes for detecting AS often rely on general biomarkers such as reactive oxygen species (ROS) or proteases, which lack specificity. To address this limitation, we developed a novel CHE-responsive fluorescent probe, NR-CHE, which utilizes cholic acid as the recognition group. This probe was synthesized by an esterification reaction between cholic acid and a lipid droplet-targeting near-infrared dye, NR-OH. The NR-CHE probe integrated the lipid droplet-targeting capability of NR with the specific response of CHE, thus offering a unique affinity for cells with lipid abnormalities and enabling precise imaging of atherosclerosis. In vitro experiments demonstrated that NR-CHE exhibited superior optical properties, with a detection limit of 0.076 U/mL. Tests involving 32 common biological interferents confirmed that the recognition group cholic acid provided high selectivity to the probe. Cell experiments further validated that NR-CHE is an effective tool for monitoring endogenous CHE in live cells. Comprehensive fluorescence imaging assessments in an AS mouse model showed that NR-CHE delivered exceptional imaging accuracy. As an extended application, NR-CHE also demonstrated potential in image-guided surgical resection in a liver cancer model. Collectively, NR-CHE holds great promise as a tool for the accurate diagnosis of AS and for guiding tumor resection surgery. [Display omitted] • Probe NR-CA selected cholic acid as a novel recognition group for CHE. • NR-OH has high fluorescence quantum yield. • CHE can be well targeted to atherosclerotic sites, and NR-OH has strong lipid droplet targeting ability. • With the dual targeting ability of CHE and NR-OH, the probe has strong specificity imaging for atherosclerotic. [ABSTRACT FROM AUTHOR]

At present, surgical resection is the primary clinical treatment method for pancreatic cancer. Accurate assessment of resectability is crucial for effective treatment planning. This paper focuses on the detection of carbohydrate antigen 125 (CA125), the in vitro biomarker for determining the resectability of pancreatic cancer. We prepared a highly stable electrochemiluminescence (ECL) luminophore, Zn-PTC, by coordinating perylene tetracarboxylic acid (PTCA) with Zn²⁺ ions. However, the current applications of Zn-PTC as ECL luminophores face challenges due to their high luminescence potential. To address these challenges, we introduced the ECL resonance energy transfer (ECL-RET) strategy and synthesized a composite material, BNCs@Zn-PTC, to achieve low-potential anodic ECL luminescence. In the ECL-RET system, Zn-PTC serves as the energy donor, while gold-silver bimetallic nanoclusters (Au-Ag BNCs) act as the energy acceptor. UV-Vis spectra of Au-Ag BNCs partially overlapped with the ECL spectra of Zn-PTC, which facilitate to effective ECL-RET between the donor and the acceptor. Utilizing BNCs@Zn-PTC as ECL luminophores, we constructed a strand displacement reaction-catalyzed hairpin assembly (SDR-CHA) dual in vitro amplified ECL sensor to detect the target CA125. Under optimal experimental conditions, the sensor had a linear detection range at CA125 concentration from 1 μU mL−1 to 10 U mL−1, with a detection limit of 0.24 μU mL−1. This study presents a novel approach for developing low-potential ECL-emitting luminophores with significant potential in clinical applications. • Au-Ag BNCs and Zn-PTC act as acceptors and donors, respectively, resulting in efficient ECL-RET. • BNCs@Zn-PTC combines the advantages of Au-Ag BNCs and Zn-PTC to achieve low-potential ECL at the anode. • The SDR-CHA dual enzyme-free amplification strategy enhances the sensitivity of this ECL biosensor. • This ECL biosensor provides a new strategy for prognosis prediction of pancreatic cancer by detecting the level of CA125. [ABSTRACT FROM AUTHOR]

Colitis is considered a significant risk factor for the development and progression of colorectal cancer due to excessive inflammation formed as a result of inflammatory bowel disease (IBD), which is linked to colorectal cancer development. Colorectal cancer often lacks overt symptoms in its early stages, leading to late-stage diagnosis in most patients. Therefore, timely diagnosis and differentiation of colitis and colorectal cancer are crucial. This study introduces a novel activatable carboxylesterase 2 (CES2) fluorescent probe, DBF-CES2, consisting of a cationic indolium fluorophore and a CES2-specific benzyl ester recognition group. The probe operates via the intramolecular charge transfer (ICT) mechanism. Upon binding and hydrolysis by CES2, a potent electron-donating hydroxyl group is released, enhancing the ICT effect and increasing fluorescence intensity, emitting red fluorescence light (λ em = 680 nm). The probe had a large Stokes shift of 167 nm and a detection limit as low as 0.70 ng/mL. It also had high selectivity, sensitivity, and biocompatibility. Cellular imaging experiments demonstrated that CES2 expression levels in colorectal cancer cells were higher than those in normal cells. The DBF-CES2 probe specifically recognized endogenous CES2 in colorectal cancer cells, promptly distinguishing them from normal cells. In vivo imaging in mice confirmed that the probe could differentiate between colitis and colorectal cancer, allowing for the assessment of the therapeutic effects of two drugs. The synthesized CES2-targeting organic small molecule fluorescent probe DBF-CES2 is a new molecular tool for the early diagnosis of colitis and colorectal cancer-related diseases, holding significant potential in clinical diagnostics. • We developed DBF-CES2, a CES2-specific fluorescent probe with a cationic indolium fluorophore and benzyl ester group. • The detection limit of the DBF-CES2 probe was as low as 0.70 ng/mL. • The DBF-CES2 probe achieved fluorescence imaging of CES2 in both in vitro and in vivo settings. • This probe shows potential for early diagnosis of colorectal cancer and colitis. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel nano-capsule does not require any additional manipulation, thus reducing the waiting time for efficacy assessment. • Utilising the enhanced permeability and retention (EPR) effect, avoid damage to normal cells and achieve good targeting. • The synthesized nano-capsules are capable of loading various types of drugs, thereby enhancing drug screening selectivity. Chemotherapy has become a common treatment for osteosarcoma, a malignant tumour, due to its relatively low pain. However, traditional monitoring of the efficacy of chemotherapeutic drugs is often limited by the targeting ability of the drug and the probe, resulting in a significant reduction in the effectiveness of the probe in locating the drug at the point of action. Therefore, the development of nano-capsules for simultaneous delivery of the drug and the monitoring probe to the tumour site for simultaneous monitoring of the therapeutic effect of chemotherapeutic drugs is essential. In response to this demand, a novel nano-capsule, NG@Au-pep@DOX, was developed for personalized and precise cancer treatment. This system facilitates the targeted delivery of an apoptotic probe (Au-pep) and an anti-cancer drug to cancer cells. The nanogel delivery system ensures efficient, low side effect drug delivery combined with apoptosis probes to monitor efficacy in real time. The designed nano-capsule consists of a caspase-3 probe with a detection limit of 0.101 ng/μL. It can encapsulate doxorubicin with an encapsulation rate of 93.94 % and a loading rate of 5.68 %. We used fluorescence microscopy, flow cytometry and other methods and through the construction of 3D cell microspheres, live and dead cell staining, cell scratching, Transwell experiments, etc. to investigate the prospects of the constructed nanocapsules in biological cells, and applied them to mice, and all of them achieved the expected results. This integrated approach can be used to address the long waiting times inherent in chemotherapy efficacy monitoring and to improve the accuracy of drug as well as probe targeting. It represents a promising strategy for the accurate and personalized treatment of osteosarcoma. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel nano-capsule does not require any additional manipulation, thus reducing the waiting time for efficacy assessment. • Utilising the enhanced permeability and retention (EPR) effect, avoid damage to normal cells and achieve good targeting. • The synthesized nano-capsules are capable of loading various types of drugs, thereby enhancing drug screening selectivity. Chemotherapy has become a common treatment for osteosarcoma, a malignant tumour, due to its relatively low pain. However, traditional monitoring of the efficacy of chemotherapeutic drugs is often limited by the targeting ability of the drug and the probe, resulting in a significant reduction in the effectiveness of the probe in locating the drug at the point of action. Therefore, the development of nano-capsules for simultaneous delivery of the drug and the monitoring probe to the tumour site for simultaneous monitoring of the therapeutic effect of chemotherapeutic drugs is essential. In response to this demand, a novel nano-capsule, NG@Au-pep@DOX, was developed for personalized and precise cancer treatment. This system facilitates the targeted delivery of an apoptotic probe (Au-pep) and an anti-cancer drug to cancer cells. The nanogel delivery system ensures efficient, low side effect drug delivery combined with apoptosis probes to monitor efficacy in real time. The designed nano-capsule consists of a caspase-3 probe with a detection limit of 0.101 ng/μL. It can encapsulate doxorubicin with an encapsulation rate of 93.94 % and a loading rate of 5.68 %. We used fluorescence microscopy, flow cytometry and other methods and through the construction of 3D cell microspheres, live and dead cell staining, cell scratching, Transwell experiments, etc. to investigate the prospects of the constructed nanocapsules in biological cells, and applied them to mice, and all of them achieved the expected results. This integrated approach can be used to address the long waiting times inherent in chemotherapy efficacy monitoring and to improve the accuracy of drug as well as probe targeting. It represents a promising strategy for the accurate and personalized treatment of osteosarcoma. [ABSTRACT FROM AUTHOR]

[Display omitted] • Combination of AA-based IDMS and mass balance approach for hGH quantification. • Mass balance method quantifies impurities in hGH using independent techniques. • Accurate hGH purity obtained without calibration graphs in AA-based IDMS. Growth hormone plays an unreplaceable role in regulating human growth and promoting protein synthesis, etc. For this reason, accurate quantification of its purity has become a focus of attention in the pharmaceutical industry and medical research. Herein, the purity assessment of human growth hormone (hGH) was established on the basis of mass balance approach and amino acid (AA)-based isotope dilution mass spectrometry (IDMS). In the first method, hGH purity was quantified by the determination of all the impurities in a hGH study material. In the second method, hGH purity was assessed by quantifying hydrolyzed AAs, e.g. leucine (Leu), phenylalanine (Phe), and proline (Pro). To accurately quantify these AAs, the corresponding isotope-labeled AAs were used as internal standards using high-performance liquid chromatography- mass spectrometry (HPLC-MS). The results of the two methods for determining the purity of hGH were consistent, with the mass balance method giving a result of (0.352 ± 0.010) g/g and IDMS a result of (0.363 ± 0.028) g/g. The work in this study could give a benefit for protein quantification and provides a reference for the development of hGH certified reference materials. [ABSTRACT FROM AUTHOR]

Thyroid cancer always appears insidiously with few noticeable clinical symptoms. Due to its limitations, conventional ultrasound imaging can lead to missed or misdiagnosed cases. Surgery is still the primary treatment method of thyroid cancer, but removal of surrounding healthy tissues to minimize recurrence leads to overtreatment and added patient suffering. To address this challenge, herein, a nitroreductase (NTR) fluorescent probe, Ox-NTR, has been developed for detecting thyroid cancer and tracking the surgical removal of thyroid tumors by fluorescence imaging. The conjugated structure of oxazine 1 was disrupted, significantly reducing the issue of high background signals, thus effectively achieving low background fluorescence. Under hypoxic conditions, the nitro group of Ox-NTR can be reduced to an amine and subsequently decomposed into oxazine 1, emitting intense red fluorescence. Ox-NTR has a low detection limit of 0.09 μg/mL for NTR with excellent photostability and selectivity. Cellular studies show that Ox-NTR can effectively detect NTR levels in hypoxic thyroid cancer cells. Moreover, the ability of Ox-NTR of rapid response to thyroid cancer in vivo is confirmed by fluorescence imaging in mice, distinguishing tumors from normal tissues due to its superior low background fluorescence. Utilizing this fluorescence imaging method during surgical resection can guide the removal of tumors, preventing both missed tumor tissues and accidental removal of healthy tissue. In summary, the novel Ox-NTR offers precise detection capabilities that provide significant advantages over traditional imaging methods for thyroid cancer diagnosis and treatment, making it a valuable tool to guide tumor removal in surgical procedures. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • The nanosensor is enriched in lung area through atomization, which can effectively reflect the treatment outcome. • The innovative visual platform that can simultaneously monitor markers of apoptosis and oxidative stress. • Changes in marker levels are detected by inducing Ca2+ overload. Lung cancer, as one of the major diseases that endanger human health, has a very high fatality rate. Consequently, effective evaluation of clinical treatment outcomes for lung cancer is crucial for the formulation of subsequent treatment plans for patients. In this work, we utilized amorphous calcium carbonate nanoparticles (CaCO 3 NPs) as sources of calcium ions (Ca2+) to develop CPs (CaCO 3 @PDA) core–shell nanoprobes. Concurrently, we functionalized the surface of gold nanoparticles with Cy5.5-peptide, AS1411, and (4-aminosulfonylphenyl) boronic acid (4-APBA) to produce APAAs (Au NPs@pep-AS1411-(4-APBA)), which were further assembled with CPs using PEG to construct an innovative explosive nanosensor, CPAs (CaCO 3 @PDA-APAAs). The CPs component of the nanosensor could cause the release of a substantial amount of Ca2+ in response to the tumor microenvironment (TME), which in turn induced cellular Ca2+ overload and subsequent apoptosis. This event triggers caspase-3 activation, causing the cleavage of a specific peptide sequence (DEVD), resulting in the fluorescence signal being reinstated. Additionally, the 4-APBA moiety on the probe interacted with H 2 O 2 resulting in alterations in surface-enhanced Raman spectroscopy (SERS) signals, which aided in the detection of reactive oxygen species (ROS) during the physiological processes. By utilizing atomization, the nanoprobes were strategically deposited in the affected lung regions to enhance the fluorescence imaging capabilities and effectively mirror the therapeutic outcomes. Overall, the CPAs explosive nanosensor has a potential in advancing the non-invasive visual monitoring of lung cancer prognosis and can be a valuable tool in ongoing efforts to improve the management of this challenging disease. [ABSTRACT FROM AUTHOR]

[Display omitted] • Developed a novel near-infrared fluorescent probe, NRO-βgal, for detecting endogenous β-galactosidase. • The probe demonstrated high selectivity and sensitivity towards β-galactosidase with a low detection limit (LOD = 0.2 U/L) and rapid response time (within 10 min). • NRO-βgal enables effective imaging of β-galactosidase levels in ovarian cancer mouse models, contributing to advancements in tumor detection and surgical interventions. The advancement of biological imaging techniques critically depends on the development of novel near-infrared (NIR) fluorescent probes. In this study, we introduce a designed NIR fluorescent probe, NRO-βgal, which exhibits a unique off–on response mechanism to β-galactosidase (β-gal). Emitting a fluorescence peak at a wavelength of 670 nm, NRO-βgal showcases a significant Stokes shift of 85 nm, which is indicative of its efficient energy transfer and minimized background interference. The probe achieves a remarkably low in vitro detection limit of 0.2 U/L and demonstrates a rapid response within 10 min, thereby underscoring its exceptional sensitivity, selectivity, and operational swiftness. Such superior analytical performance broadens the horizon for its application in intricate biological imaging studies. To validate the practical utility of NRO-βgal in bio-imaging, we employed ovarian cancer cell and mouse models, where the probe's efficacy in accurately delineating tumor cells was examined. The results affirm NRO-βgal's capability to provide sharp, high-contrast images of tumor regions, thereby significantly enhancing the precision of surgical tumor resection. Furthermore, the probe's potential for real-time monitoring of enzymatic activity in living tissues underscores its utility as a powerful tool for diagnostics in oncology and beyond. [ABSTRACT FROM AUTHOR]

Owing to the adverse effects of oxytetracycline (OTC) residues on human health, it is of great importance to construct a rapid and effective strategy for OTC detection. Herein, we developed a dual-response fluorescence sensing platform based on molybdenum sulfide quantum dots (MoS 2 QDs) and europium ions (Eu3+) for ratiometric detection of OTC. The MoS 2 QDs, synthesized through an uncomplicated one-step hydrothermal approach, upon OTC integration into the MoS 2 QDs/Eu3+ sensing system, exhibit a significant quenching of blue fluorescence due to the inner filter effect (IFE), simultaneously enhancing the distinct red emission of Eu3+ at 624 nm, a phenomenon attributed to the antenna effect (AE). This sensor demonstrates exceptional selectivity and sensitivity towards OTC, characterized by a linear detection range of 0.2–10 μM and a notably low detection limit of 2.21 nM. Furthermore, we achieved a visual semi-quantitative assessment of OTC through the discernible fluorescence color transition from blue to red under a 365 nm ultraviolet lamp. The practical applicability of this sensor was validated through the successful detection of OTC in milk and mutton samples, underscoring its potential as a robust tool for OTC monitoring in foodstuffs to safeguard food safety. [Display omitted] • Dual-response fluorescence sensor was constructed by simply mixing MoS 2 QDs and Eu3+ for the ratiometric detection of OTC. • The sensor was constructed without complex processing and can rapidly respond to OTC within 80 s. • Visual semi-quantitative detection of OTC can be achieved by distinguishing the fluorescence variation with the naked eye. • The sensor has high sensitivity to OTC with a LOD of 2.21 nM and has been used to detect OTC in milk and mutton samples. [ABSTRACT FROM AUTHOR]

Carboxylesterase 2 (CES2) plays a critical role in the metabolism of ester- and amide-containing drugs and thus has an impact on drug efficacy and toxicity. This study introduces QVJ-CES2, a near-infrared fluorescent probe designed to enhance thyroid cancer diagnosis through CES2 enzyme activity and distinct cellular viscosity of thyroid cells. The probe's dual-response mechanism significantly amplified fluorescence in high-viscosity environments, thus had high sensitivity. Our findings revealed that QVJ-CES2 could detect CES2 activity with a limit of detection as low as 1.9 ng/mL. In vitro experiments confirmed the rapid and selective response of QVJ-CES2 to CES2 and the ability to distinguish cancer cells from their normal cells with high specificity. Most importantly, the fluorescence intensity difference between cancerous and normal cells after incubation with the probe was as high as 7-fold, attributable to the synergistic enzyme and viscosity cascade response. Further, in vivo studies demonstrated that the probe was effective in accurately identifying thyroid cancer tissues, showing that it is a promising tool for early cancer detection and precise surgical interventions. • Dual-response mechanism boosts fluorescence in viscous settings, enhancing sensitivity. • QVJ-CES2 showcases exceptional detection capabilities for CES2, with a sensitivity threshold as low as 1.9 ng/m. • Fluorescence difference between cancerous and normal cells is 7-fold due to enzyme-viscosity response. • In vivo studies show the probe accurately identifies thyroid cancer tissues. [ABSTRACT FROM AUTHOR]

A highly sensitive fluorescence-based assay for cholesterol detection was developed using water-dispersible green-emitting silicon nanoparticles (SiNPs) as a fluorescence indicator and enzyme-catalyzed oxidation product PPDox (Bandrowski's base) as a quencher. The SiNPs were facilely synthesized via a simple, one-step hydrothermal treatment using 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane (AEEA) as the silicon source, which has ultrahigh quantum yield and low phototoxicity. Under the catalysis of cholesterol oxidase (ChOx), hydrogen peroxide (H2O2) was generated as a result of cholesterol oxidation. Utilizing p-phenylenediamine (PPD) as the substrate for horseradish peroxidase (HRP) in the presence of H2O2 led to the production of PPDox. Based upon the inner filter effect (IFE), the established ultrasensitive fluorescent assay could accurately measure cholesterol. The limit of detection (LOD) of the assay was 0.018 μM with a linear range of 0.025–10 μM. The results for the detection of real serum samples by the proposed assay were comparable to those by a commercial reagent kit, demonstrating that our proposed strategy has high application potential in disease diagnosis and other related biological studies. [ABSTRACT FROM AUTHOR]

Long-range surface plasmon resonance (LRSPR) has demonstrated excellent performance in sensing and detection, due to its higher accuracy and sensitivity compared with conventional surface plasmon resonance (cSPR). In this work, we establish an LRSPR biosensor which employs PDA/Ti3C2-MXene/PDA-gold film as a sensing substrate and gold nanoparticles (AuNPs) as enhancers. Ti3C2-MXene is an emerging two-dimensional (2D) layered material which is used extensively in immunoassay and biosensing. The sensing substrate comprises two polydopamine (PDA) films between which is sandwiched a Ti3C2-MXene film based on a gold film, which provides a large surface area and abundant binding sites to rabbit anti-human IgG (Ab1). Sandwich amplification is adopted to enhance the sensitivity of the LRSPR biosensor, and AuNPs/staphylococcal protein A (SPA)/mouse anti-human IgG (Ab2) composites are introduced into the flow cell as enhancers after the immune binding of human IgG to Ab1. The antigen (human IgG) detection range is 0.075 μg mL−1 to 40 μg mL−1, and the limit of detection is almost 20 times lower than that for cSPR biosensors. This novel LRSPR biosensor demonstrates excellent performance in immune sensing over a broad detection range and a low limit of detection. Subsequent modification of the LRSPR sensing platform could be made for extensive application in various biological detection fields. [ABSTRACT FROM AUTHOR]

In the present study, we propose a novel method for the extraction of parabens in personal care products. A new, simple adsorptive material was obtained by combining metal‐organic frameworks and melamine sponges using the adhesive property of polyvinylidene fluoride. This new material, metal‐organic frameworks/melamine sponges, was found to be particularly suitable for solid‐phase extraction. The structural characteristics of metal‐organic frameworks/melamine sponges were first analyzed by scanning electron microscopy. Subsequently, solid‐phase extraction was performed on sample solutions, and the extracted substances were then analyzed by high‐performance liquid chromatography. Following optimization of important experimental conditions, excellent recovery rates were obtained. Our novel method was then applied to the extraction of four parabens (methylparahydroxybenzoates, ethylparahydroxybenzoates, propylparahydroxybenzoates, and butylparahydroxybenzoates) from real samples. The results yielded limits of detection of 0.26–0.41 ng/mL. The inter‐ and intra‐day recoveries were 104.0–109.7% and 91.2–98.1%, respectively (relative standard deviation, <13.8%). [ABSTRACT FROM AUTHOR]

Pancreatic ductal adenocarcinoma (PDAC) poses significant diagnostic challenges due to its asymptomatic nature in its early stages, low specificity of conventional in vitro assays, and limited efficacy of surgical interventions. However, clinical specificity of the current serum biomarkers is suboptimal, leading to diagnostic inaccuracies and oversights. Therefore, this study introduced a novel dual-target electrochemiluminescence (ECL) biosensor to address these critical issues. The ECL biosensor synergistically employs the serum biomarker MUC1 and microRNA-196a to detect early-stage PDAC precisely. While MUC1 is a differential marker between normal and cancerous pancreatic cells, its standalone diagnostic performance is limited. However, integrating miRNA-196a as a complementary marker substantially enhances the specificity of the assay. This biosensor exhibits distinct ECL signal modulation—"on-off" in the presence of MUC1 and "off-on" upon concurrent detection of MUC1 and miRNA-196a. The biosensor achieves remarkably low limits of detection (LODs) at 0.63 fg mL−1 and 4.57 aM for MUC1 and miRNA-196a, respectively. Thus, it facilitates the real-time differentiation between human normal pancreatic (hTERT-HPNE) and pancreatic cancer (PANC-1) cells in authentic biological matrices. This innovative approach heralds a significant advancement in the early and specific detection of PDAC, offering promising prospects for clinical translation and the broader landscape of cancer diagnostics. [ABSTRACT FROM AUTHOR]