Probe For Detection Research Articles

Targeted synthesis of a 3D covalent organic framework with fjh topology exhibiting high photoluminescence: A robust platform for sensitive detection of furantoin

The inappropriate use of antibiotics poses significant risks to both the environment and human health, necessitating the development of accurate and sensitive detection methods. Fluorescence detection, particularly utilizing three-dimensional (3D) covalent organic frameworks (COFs), stands out as a promising avenue. Unlike two-dimensional COFs, 3D COFs can mitigate fluorescence quenching resulting from non-radiative energy loss, primarily attributed to π-π interlayer stacking. In this study, by carefully selecting and designing the building blocks, we synthesized a 3D COF named PyTTA-TTFB-COF with fjh topology and remarkable photoluminescence. This was achieved through the combination of a 4-connected square chromophore, 1,3,6,8-Tetrakis(4-aminophenyl) pyrene, with a 3-connected triangle, 1,3,5-trimethyl-2,4,6-tris(4-formylphenyl) benzene, possessing a specific stereo conformation. Significantly, PyTTA-TTFB-COF exhibits a high photoluminescence quantum yield, notably reaching 60.1% in acetonitrile. Moreover, it displays substantial fluorescence quenching when exposed to furantoin, surpassing the performance observed with other antibiotics. Competitive experiments have confirmed that PyTTA-TTFB-COF can serve as a specific fluorescent probe for the interference-free detection of furantoin.

Two-Photon Nanoparticle Probe for Formaldehyde Detection via the AILE Luminescence Mechanism

Two-Photon Nanoparticle Probe for Formaldehyde Detection via the AILE Luminescence Mechanism

Ultrasensitive and Highly Selective Detection of Staphylococcus aureus at the Single-Cell Level Using Bacteria-Imprinted Polymer and Vancomycin-Conjugated MnO2 Nanozyme.

Pathogenic bacterial infections, even at extremely low concentrations, pose significant threats to human health. However, the challenge persists in achieving high-sensitivity bacterial detection, particularly in complex samples. Herein, we present a novel sandwich-type electrochemical sensor utilizing bacteria-imprinted polymer (BIP) coupled with vancomycin-conjugated MnO2 nanozyme (Van@BSA-MnO2) for the ultrasensitive detection of pathogenic bacteria, exemplified by Staphylococcus aureus (S. aureus). The BIP, in situ prepared on the electrode surface, acts as a highly specific capture probe by replicating the surface features of S. aureus. Vancomycin (Van), known for its affinity to bacterial cell walls, is conjugated with a Bovine serum albumin (BSA)-templated MnO2 nanozyme through EDC/NHS chemistry. The resulting Van@BSA-MnO2 complex, serving as a detection probe, provides an efficient catalytic platform for signal amplification. Upon binding with the captured S. aureus, the Van@BSA-MnO2 complex catalyzes a substrate reaction, generating a current signal proportional to the target bacterial concentration. The sensor displays remarkable sensitivity, capable of detecting a single bacterial cell in a phosphate buffer solution. Even in complex milk matrices, it maintains outstanding performance, identifying S. aureus at concentrations as low as 10 CFU mL-1 without requiring intricate sample pretreatment. Moreover, the sensor demonstrates excellent selectivity, particularly in distinguishing target S. aureus from interfering bacteria of the same genus at concentrations 100-fold higher. This innovative method, employing entirely synthetic materials, provides a versatile and low-cost detection platform for Gram-positive bacteria. In comparison to existing nanozyme-based bacterial sensors with biological recognition materials, our assay offers distinct advantages, including enhanced sensitivity, ease of preparation, and cost-effectiveness, thereby holding significant promise for applications in food safety and environmental monitoring.

Nitrogen and Chlorine Co-Doped Carbon Dots with Yellow-Green Emission as a Ratiometric Fluorescent and Colorimetric Dual-Signal Probe for Quercetin Detection and Cell Imaging

Despite the emergence of numerous carbon dots (CDs)-based sensors, most of them are fluorescent probes. To improve the reliability of the results, using ratiometric fluorescence/UV-vis absorption dual-signal probes is an effective method. Herein, nitrogen and chlorine co-doped carbon dots (N, Cl-CDs) with yellow-green fluorescence were prepared and used as a dual-function probe for ratiometric fluorescence/UV-vis. The detection range of the fluorescence method was 0.05–78[Formula: see text][Formula: see text]M, and the limit of detection (LOD) was 1.2[Formula: see text]nM (3[Formula: see text]/s). For the colorimetric method, the linear range was 0.05–186[Formula: see text][Formula: see text]M with LOD of 10.7[Formula: see text]nM. Importantly, the N, Cl-CDs were successfully used to detect Quercetin (QT) in actual water samples. Besides, due to their good biocompatibility, the N, Cl-CDs were applied to in vivo biological imaging of oocysts and shown the potential for environmental survey and biological assay.

Dual-ligand lanthanide metal-organic framework based ratiometric fluorescent platform for visual monitoring of aminoglycoside residues in food samples

Herein, a dual-emission Eu metal-organic framework (Eu-MOF) is prepared and used as the ratiometric fluorescence probe for ultrasensitive detection of aminoglycoside antibiotics (AGs). Due to the strong hydrogen bond interactions between AGs and Eu-MOF, the blue emission is enhanced while the red emission has little fluctuation in Eu-MOF with the addition of AGs, thus a good linear relationship with the logarithm of AGs concentrations from 0.001 to 100 μg/mL can be established for quantitative analysis. Good sensitivity with the detection limit of 0.33 ng/mL for apramycin, 0.32 ng/mL for amikacin and 0.30 ng/mL for kanamycin is achieved. The proposed assay demonstrates good selectivity and applicability for determination of AGs in real milk and honey samples. The Eu-MOF materials are further fabricated as fluorescent test papers for facile visual detection. The as-established ratio fluorescence platform offers a portable and economical way for rapid monitoring AGs residues in complex food samples.

Development of a multiplex one-tube loop-mediated isothermal amplification method for rapidly simultaneous detection of the mecA and nuc genes in methicillin-resistant Staphylococcus aureus

This study developed a multiplex one-tube loop-mediated isothermal amplification method using fluorescent dye-labeled DNA probes (mfLAMP) for the rapid simultaneous detection of the nuc (S. aureus-specific marker) and mecA genes (PBP2a-specific marker) in methicillin-resistant Staphylococcus aureus (MRSA). In the mfLAMP method, a graphene oxide (GO) was used as an effective adsorbent to eliminate free fluorescent dye-labeled DNA probes (mecAf-probe: Cy5-ssDNA-Biotin and nucf-probe: FAM-ssDNA-Biotin) present in negative results. The samples were then measured using a developed program that enable simultaneous detection of fluorescein (FAM) and Cyanine5 (Cy5). Green fluorescence represents the detection of the nuc gene, red fluorescence indicates the detection of the mecA gene, and yellow fluorescence signifies the detection of MRSA. The mfLAMP was specific to MRSA and could detect 10°CFU/mL of MRSA in standard buffer and artificially inoculated irrigation water. The recovery rate from contaminated irrigation water ranged from 100.41 to 109.85 %. This study is the first to report the mfLAMP using GO, which could be point-of-care testing for the rapid and simultaneous detection of MRSA's nuc and mecA genes. The results demonstrate that the mfLAMP will be a novel tool for simultaneously detecting more than two target genes or bacteria within 1 h without an enrichment step.

Coumarin-hemicyanine-based ratiometric fluorescent probes for detection of strong acidity

Fluorescent probes for determination of strongly acidic pH values are urgently needed, especially the ones with ratiometric signal changes. Here, two fluorescent probes (CP and CyC) based on coumarin-hemicyanine were synthesized. Both probes emitted red fluorescence under weakly acidic to weakly alkaline conditions, whereas blue fluorescence under strongly acidic conditions. Notably, probe CP displayed good stability, water solubility, anti-interference ability, repeated utilization and instant response. Encouraged by the good performance, probe CP based test strips were used to indicate the pH of aqueous solutions, and to detect HCl or NH3 vapor in air reversibly.

Turn-on fluorescent probe for ultrafast detection of phosgene in the environment and household bleach; its applications in live cell imaging

Phosgene is a vital industrial gas that might substantially imperil public safety in the case of an accident or terrorist attack due to its extreme toxicity and history of use as a chemical warfare agent. Herein we built a simple photoinduced electron transfer-intramolecular charge transfer based turn-on fluorescent probe for ultrafast detection of phosgene within ≤ 3 s. The probe provides low detection limit (0.01 ppm) with distinct colour and fluorescence changes only in the presence of phosgene. With the help of a readily available colour smartphone app, the probe-loaded paper strips allowed for the direct visualization and quantitative measurement of phosgene vapour. Using the probe-coated strips to detect phosgene that evolved from common household bleach. Finally, the probe was utilized to detect phosgene in living cells.

An activatable fluorescence probe for rapid detection and in situ imaging of β-galactosidase activity in cabbage roots under heavy metal stress

β-Galactosidase (β-gal), an enzyme related to cell wall degradation, plays an important role in regulating cell wall metabolism and reconstruction. However, activatable fluorescence probes for the detection and imaging of β-gal fluctuations in plants have been less exploited. Herein, we report an activatable fluorescent probe based on intramolecular charge transfer (ICT), benzothiazole coumarin-bearing β-galactoside (BC-βgal), to achieve distinct in situ imaging of β-gal in plant cells. It exhibits high sensitivity and selectivity to β-gal with a fast response (8 min). BC-βgal can be used to efficiently detect the alternations of intracellular β-gal levels in cabbage root cells with considerable imaging integrity and imaging contrast. Significantly, BC-βgal can assess β-gal activity in cabbage roots under heavy metal stress (Cd2+, Cu2+, and Pb2+), revealing that β-gal activity is negatively correlated with the severity of heavy metal stress. Our work thus facilitates the study of β-gal biological mechanisms.

Ferrocene probe-assisted fluorescence quenching of PEI-carbon dots for NO detection and the logic gates based sensing of NO enabled by trimodal detection

Our research demonstrates the effectiveness of fluorescence quenching between polyethyleneimine functionalised carbon dots (PEI-CDs) and cyclodextrin encapsulated ferrocene for fluorogenic detection of nitric oxide (NO). We confirmed that ferrocene can be used as a NO probe by observing its ability to quench the fluorescence emitted from PEI-CDs, with NO concentrations ranging from 1 × 10–6 M to 5 × 10–4 M. The photoluminescence intensity (PL) of PEI-CDs decreased linearly, with a detection limit of 500 nM. Previous studies have shown that ferrocene is a selective probe for NO detection in biological systems by electrochemical and colorimetric methods. The addition of fluorogenic NO detection using ferrocene as a probe enables the development of a three-way sensor probe for NO. Furthermore, the triple mode NO detection (electrochemical, colorimetric, and fluorogenic) with ferrocene aids in processing sensing data in a controlled manner similar to Boolean logic operations. This work presents key findings on the mechanism of fluorescence quenching between ferrocene hyponitrite intermediate and PEI-CDs, the potential of using ferrocene for triple channel NO detection as a single molecular entity, and the application of logic gates for NO sensing.

A novel “Turn-Off-On” fluorescent probe for specific sequential detection of Cu2+ and glyphosate and its application in biological imaging

As common pollutants, Cu2+ and glyphosate pose a serious threat to human health and the ecosystem. Herein, a fluorescent probe (E)-7-(diethylamino)-N'(4-(diethylamino)-2-hydroxybenzyl)-2-oxo-2H chromophore-3-carbazide (DDHC) was designed and synthesised for the sequential recognition of Cu2+ and glyphosate. DDHC has the advantages of a short synthesis path, easy-to-obtain raw materials, good anti-interference ability, and strong stability. The interaction of the DDHC-Cu2+ complexes with glyphosate allows the amino and carboxyl groups in glyphosate molecules to coordinate with Cu2+ strongly, competing for the Cu2+ in the DDHC-Cu2+ complexes and releasing the DDHC, leading to the recovery of fluorescence. The recognition was further validated through Job’s plot, HRMS, and DFT calculations. In addition, the successful recovery of Cu2+ and glyphosate in different environmental water samples fully demonstrates the practical application potential of DDHC. Especially, DDHC has low cytotoxicity and can enter zebrafish and HeLa cells, rapidly reacting with Cu2+ and glyphosate in the body, generating visible fluorescence quenching and recovery phenomena, achieving real-time visual monitoring of exogenous Cu2+ and glyphosate in zebrafish and HeLa cells. The targeting and dual selectivity of DDHC greatly enhance its potential application value in the field of detection, providing important theoretical support for studying the fate of multiple pollutants in the environment.

Hemin as a Molecular Probe for Nitric Oxide Detection in Physiological Solutions: Experimental and Theoretical Assessment.

Given its pivotal role in modulating various pathological processes, precise measurement of nitric oxide (●NO) levels in physiological solutions is imperative. The key techniques include the ozone-based chemiluminescence (CL) reactions, amperometric ●NO sensing, and Griess assay, each with its advantages and drawbacks. In this study, a hemin/H2O2/luminol CL reaction was employed for accurately detecting ●NO in diverse solutions. We investigated how the luminescence kinetics was influenced by ●NO from two donors, nitrite and peroxynitrite, while also assessing the impact of culture medium components and reactive species quenchers. Furthermore, we experimentally and theoretically explored the mechanism of hemin oxidation responsible for the initiation of light generation. Although both hemin and ●NO enhanced the H2O2/luminol-based luminescence reactions with distinct kinetics, hemin's interference with ●NO/peroxynitrite- modulated their individual effects. Leveraging the propagated signal due to hemin, the ●NO levels in solution were estimated, observing parallel changes to those detected via amperometric detection in response to varying concentrations of the ●NO-donor. The examined reactions aid in comprehending the mechanism of ●NO/hemin/H2O2/luminol interactions and how these can be used for detecting ●NO in solution with minimal sample size demands. Moreover, the selectivity across different solutions can be improved by incorporating certain quenchers for reactive species into the reaction.

Coumarin-based fluorescent probes for colorimetric and ratiometric fluorescent detection of sulfite: Structure-activity relationship

Six coumarin-based fluorescent probes were designed and synthesized for the detection of sulfite. The probes were constructed based on “fluorophore-receptor/linker-steric group” mode with N,N-diethyl-7-aminocoumarin (DEA) or 2,3,5,6-1H,4H-tetrahydro-quinolazino-(9,9a,1-gh)coumarin (THQ) as the fluorophore, 2-naphthyl ketone (N) or phenyl ketone (B) as the steric group and vinyl (1) or 1,3-butadienyl (2) as the receptor/linker. The effects of the fluorophore, the linker and the steric group on the photophysical properties and sensing performance were systematically studied. Among all the probes, DEA-N2 exhibited the most excellent spectral responses toward sulfite: upon addition of sulfite, the absorption and emission maxima shifted from 488 nm to 405 nm and–from 684 nm to 484 nm, respectively. I484/I688 displayed good linear relationship with sulfite concentration in the range of 3–50 μM, with a detection limit of 0.31 μM. The experimental results demonstrate that DEA-N2 has potential in ratiometric fluorescent imaging of mitochondrial sulfite in living cells.

Design and synthesis of Lanthanide(III) complex based luminescence probes for time-resolved luminescence detection of β-galactosidase

β-Galactosidase (β-Gal), confirmed to provide energy and participate in the galactosyl transfer reaction, is primarily over-expressed in ovarian cancer cells. Herein, detecting endogenous β-Gal is essential for the diagnosis and monitoring of primary ovarian cancer cells. In this study, we proposed two structurally related cationic Lanthanide(III) triamide complexes for highly sensitive and rapid detection of β-Gal. Moreover, LDEu02 showed a low detection limit (2.3 × 10−3 U/mL) and high specificity with high affinity for β-Gal, which had great potential to the detection of the β-Gal activity by using time-resolved fluorescence techniques.

A universal strategy for constructing high-performance silica-based AIE materials for biomedical application

As an emerging fluorophore, aggregation-induced emission luminogens (AIEgens) have received widespread attention in recent years, but the inherent drawbacks of AIEgens, such as the poor water-solubility and insufficient fluorescence stability in complex environments, restrict their performance in practical applications. Herein, we report a universal strategy based on hydrophobic dendritic mesoporous silica (HMSN) that can integrate different AIE molecules to construct multi-color fluorescent AIE materials. Specifically, HMSN with central radial pores was used as a powerful carrier for direct loading AIE molecules and restricting their intramolecular motions. Due to the pore-domain restriction effect and hydrophobic interaction, the obtained silica-based AIE materials have bright fluorescence with a maximum quantum yield of 68.38%, high colloidal/fluorescence stability, and excellent biosafety. Further, these silica-based AIE materials can be conjugated with functional antibodies to obtain probes with different targetability. After integration with immunomagnetic beads, the prepared detection probes achieved the quantitative detection of cardiac troponin I with the limit of detection (LOD) of 0.508 ng/mL. Overall, the targeting probes stemming from silica-based AIE materials can not only achieve cell-specific imaging, but quantify the number of Jurkat cells (LOD = 270 cells/mL) to further determine the specific etiology of the disease.

Green Synthesis of CQDs via the Trunks of Bauhinia purpurea as Fluorescence Probes for Rapid and Accurate Detection of Quinoline Yellow.

Carbon quantum dots (CQDs) were greenly synthesized via a single-step hydrothermal method, using the trunks of Bauhinia purpurea as the carbon source. They exhibited good dispersibility, water solubility, high sensitivity, and great stability with a spherical form and a particle size of 2.68 ± 0.32 nm. By utilizing the inner filter effect and dynamic quenching effect, the fluorescence quenching of CQDs can be induced to detect quinoline yellow. Detailed experimental results showed that the change rate of fluorescence intensity of CQDshadagood linearrelationshipwith varying concentrations of quinoline yellow (2-128 µmol/L). It can be clearly observed that the fluorescence quenching occurred within 1 min, its correlation coefficient (R2) is 0.9912, and the detection limit (DL) is 1.7884 μmol/L, substantially lower than the maximum concentration stipulated by the national standard of 209.5 µmol/L. Furthermore, quinoline yellow had been successfully detected in real beverage samples using CQDs, with the recovery rates of 90.6%-110.4% and the relative standard deviation (RSD) ≤ 6.3% and it also showed great anti-interference and selectivity. These findings indicate that the detected quinoline yellow of CQDs possess substantial promise for a wide range of applications within the detected artificial food colors field.

Green synthesized AgNPs as a probe for colorimetric detection of Hg (II) ions in aqueous medium and fluorescent imaging in liver cell lines and its antibacterial activity

The present research aimed at green synthesis of Ag nanoparticles (AgNPs) based colorimetric sensor using persimmon leaf extract (PLE) for selective detection of mercuric ion (Hg2+). Optimization of reaction conditions viz. pH, concentration of PLE, time was done and further AgNPs were characterized using UV, IR, FE-SEM, EDX, XRD and TEM analysis. The developed AgNPs were evaluated for the selective colorimetric detection of Hg2+ in aqueous medium and fluorescence imaging of Hg2+ ions in liver cell lines. Later, the antibacterial activity of AgNPs was performed against S. aureus and E. coli. The findings of the study revealed that PLE mediated AgNPs exhibited notable limit of detection up to 0.1 ppb, high efficiency, and stability. The antibacterial study indicated that developed AgNPs has impressive bacterial inhibiting properties against the tested bacterial strains. In conclusion, developed biogenic AgNPs has high selectivity and notable sensitivity towards Hg2+ ions and may be used as key tool water remediation.Graphical abstract

Composite Eu@Cd-CP as a fluorescent probe for the detection of some food additives

A transition metal coordination polymer (CP), [Cd(Hdpcp)]n (Cd-CP) was prepared based on 3-(2,4-dicarboxyphenyl)-6-carboxypyridine ligand (H3dpcp), and then its composite Eu@Cd-CP was synthesized by the post-modification through loading Eu3+ ions on Cd-CP. Eu@Cd-CP has outstanding fluorescence stability in aqueous solution with a wide range of pH. Furthermore, Eu@Cd-CP can distinguish sodium salicylate (SS) and sodium dehydroacetate (SA) in some food additives by quenching the characteristic fluorescence of Eu3+ ion. Eu@Cd-CP is the first known CP-based fluorescent probe for selective detection of SS and SA. In addition, the fluorescence mechanisms of discerning above analytes by Eu@Cd-CP have been thoroughly evaluated. It has found that synergistic effect of the dynamic process, photoinduced electron transfer (PET) process, energy absorption competition, and formation of Eu-O bonding interactions in sensing SA lead to the fluorescence quenching of Eu@Cd-CP. The fluorescence response mechanism of Eu@Cd-CP with SA is ascribed to the combination of the dynamic process, PET process, and energy absorption competition. A series of portable devices based on Eu@Cd-CP including fluorescence test strips, lamp beads, and composite films were developed to discern SS and SA via visual changes in luminescence color. This composite material can be potentially used as a multifunctional fluorescent probe for practical applications.

Development of a quantum dots based immunochromatographic strip for rapid and on-site detection of African swine fever virus

African swine fever (ASF) is a lethal disease caused by ASF virus (ASFV), severely impacting the global swine industry. Though nuclear acid-based detection methods are reliable, they are laboratory-dependent. In this study, we developed a device-independent, user friendly and cost-effective quantum dots based immunochromatographic strip (QDs-ICS) with high specificity and sensitivity for the rapid and on-site detection of ASFV antigen. For the preparation of the QDs-ICS, we generated a monoclonal antibody (mAb) mAb-8G8 and polyclonal antibody (pAb) against ASFV-p72 protein. The pAb was labelled with QDs to be used as the detection probe and the mAb-8G8 was coated on the nitrocellulose membrane as the test line. Our results proved that the strip displayed no cross-reactivity with other swine viruses and detection limit of the QDs-ICS was down to 1 ng/mL for the ASFV-p72 protein with great reproducibility. The strip also exhibited high stability with a storage period up to 12 months under room temperature. Twenty blind samples and one hundred clinical samples were examined by the QDs-ICS, conventional PCR and real-time PCR method, respectively. Results showed that the agreement rate between the QDs-ICS and PCR method was 100%, and the agreement rate between the strip and real-time PCR was 94%. The novel QDs-ICS developed here would be an effective tool for on-site detection of ASFV.

ICP-MS based detection method combined with Au NP and Ag NP labeling for bacteremia diagnosis

Bacteremia, as a serious infectious disease, has an increasing incidence and a high mortality rate. Early diagnosis and early treatment are crucial for improving the cure rate. In this work, we proposed an inductively coupled plasma mass spectrometry (ICP-MS)-based detection method combined with gold nanoparticle (Au NP) and silver nanoparticle (Ag NP) labeling for the simultaneous detection of Salmonella and Escherichia coli (E. coli O157:H7) in human blood samples. Salmonella and E. coli O157:H7 were captured by magnetic beads coupled with anti-8G3 and anti-7C2, and then specifically labeled by Au NP-anti-5H12 and Ag NP-anti-8B1 respectively, which were used as signal probes for ICP-MS detection. Under the optimal experimental conditions, the limits of detection of 164 CFU mL-1 for Salmonella, 220 CFU mL-1for E. coli O157:H7 and the linear ranges of 400-80,000 CFU mL-1Salmonella, 400-60,000 CFU mL-1E. coli O157:H7 were obtained. The proposed method can realize the simultaneous detection of two types of pathogenic bacteria in human whole blood in 3.5 hours, showing great potential for the rapid diagnosis of bacteremia in clinic.