Recognition Probe Research Articles

Early in vitro results indicate that de-O-acetylated sialic acids increase Selectin binding in cancers

Cancers utilize a simple glycan, Sialic Acid, to engage in metastatic processes via the Sialic acid (Sia) -Selectin pathway. Selectins recognize and bind to sialylated substrates, resulting in adhesion, migration, and extravasation, however, how deviations from the canonical form of Sia regulate binding to Selectin receptors (E, L, and P) on hemopoietic cells resulting in these metastatic processes, remained a gap in knowledge. De-O-acetylated Sias has been recently shown to be an integral substrate to the binding of sialic acid binding proteins. The two proteins responsible for regulating the acetyl functional group on Sia’s C6 tail, are Sialic acid acetylesterase (SIAE) and Sialic acid O acetyltransferase (CASD1). To elucidate the contribution of functional group alterations on Sia, 9-O and 7,9-O-acetylation of Sia was modulated via the use of CRISRP-Cas9 gene editing and with Sialyl Glycan Recognition Probes, to produce either O-acetylated-Sia or de-O-acetylated- Sia, respectively. In vitro experiments revealed that increased cell surface expression of de-O-acetylated- Sia resulted in an increase in Selectin binding, enhanced cell proliferation, and increased migration capabilities both in lung and colon cancer. These results delineate for the first time the mechanistic contribution of de-O-acetylated-Sia to Selectin binding, reinforcing the importance of elucidating functional group alterations on Sia and their contribution. Without accurate identification of which functionalized form of Sia is being utilized to bind to sialic acid binding proteins, we cannot accurately produce glycan therapeutics with the correct specificity and reactivity, thus this work contributes an integral component in the development of promising therapeutic avenues, for example in the realm of enzyme antibody drug conjugates.

Molecular Probe for Specific Recognition of TKX-50: 'Luminescence-ON' Response and its Integration to a Smart Device for Surveillance.

In response to the growing concerns about the unauthorized use of advanced secondary explosives such as TKX-50 against non-combatant targets, there is an urgent need for effective detection methods or techniques to ensure efficient security screening, homeland security, and public safety. Herein, a new polymeric receptor (IV) derived from functionalized tetraphenylethylene moiety (TPE) and 1,3,5-tris(4-aminophenyl)benzene (TAPB) moietiesfor the efficient detection of TKX-50 through a 'switch ON' luminescence response upon specific binding to the explosive, is reported. The observed 'luminescence ON' response is rationalized based on a charge transfer complex formation between TKX-50 and the polymeric receptor IV (Ka = 1.7 × 104 m-1). This is validated by the steady and excited-state luminescence studies, along with detailed computational studies. The authors' presumptions are further validated with adequate control studies using an appropriate monomeric derivative (III) of TPE. Moreover, this 'luminescence ON' response can be integrated into a smart and user-friendly Internet of Things (IoT)-based prototype device. This device can effectively convert optical responses into digital output to develop an optical device for real-time detection of TKX-50 in solution. This lightweight, portable device is ideally suited for remote surveillance and monitoring of TKX-50; such examples are rare in contemporary literature.

A ratiometric fluorescent biosensor based on catalytic hairpin assembly reaction for ultrasensitive detection of aflatoxin-producing genes

Aflatoxins as the world’s most toxic contamination is metabolized by Aspergillus flavus and its production is closely related to aflatoxin-producing genes. It is significant to monitor the aflatoxin-producing genes as early as possible to prevent the contamination and spread of aflatoxins. Therefore, a label-free and free separation fluorescent biosensor using the selective cation exchange reaction in conjunction with the signal amplification of catalytic hairpin assembly (CHA) was developed for the detection of aflatoxin-producing gene utilizing CdTe quantum dots (CdTe QDs) and Nitrogen-doped carbon quantum dots (NCQDs) as the beacon molecule. There were two types of hairpin structures in this sensing system, hairpin probe 1 (HP1) was generated by Ag+ and the recognition probe with the complex C-Ag+-C structure and hairpin probe 2 (HP2) was the DNA fragments showing a hairpin arrangement. Target nor-1 gene may activate the CHA, which created a significant quantity of HP1-HP2 double-stranded DNAand recycled the target nor-1 gene. The released amounts of Ag+ suppressed the fluorescence signal of CdTe QDs, while it wasn’t observed the discernible effect on NCQDs. This fluorescent biosensor displayed the excellent sensitivity for aflatoxin-producing nor-1 gene in a dynamic range of 5 pM to 50 nM with a detection limit of 1.66 pM. This fabricated sensor also showed the visible distinguish for different concentrations of nor-1 gene. It exhibited the potential to offer vital enhancements for food quality control through a simple, fast and sensitive monitoring test system.

Electrochemical biosensor based on Novozym 435 enzymatic ring-opening polymerization for CEA detection

Carcinoembryonic antigen (CEA) is a broad-spectrum tumour marker, with its concentration levels serving as a crucial predictor of cancer diagnosis. In this study, we synthesized a polycaprolactone (PCL) macromolecular polymer via enzyme ring-opening polymerization (eROP). This polymer was then utilized as a signal amplification element in the “sandwich structure” electrochemical impedance biosensor designed for CEA detection. Initially, 3-mercaptopropionic acid (MPA) was self-assembled onto the electrode surface via a gold-sulfur bond. The carboxyl terminus of MPA was then activated using carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS). Subsequently, antibody 1 (Ab1) was immobilised on the electrode surface through the formation of an amide bond, serving as a recognition probe. To prevent non-specific binding, the remaining sites were blocked with Bovine Serum Albumin (BSA). Following the specific capture of CEA by Ab1, the unreacted amino group on the electrode surface was sealed using acrolein. Antibody-2 (Ab2) was then introduced to specifically recognize CEA, forming a classic antibody-antigen–antibody “sandwich structure.” Finally, a DMPA (2,2-dihydroxymethylpropionic acid)-PCL (Polycaprolactone) polymer was conjugated to the electrode surface as a signal amplification unit. The impedance signal strength was subsequently measured using Electrochemical Impedance Spectroscopy (EIS). Under optimal conditions, the biosensor demonstrated a wide linear range (1 pg mL−1 ∼ 100 ng mL−1) and a low detection limit of 0.38 pg mL−1. The sensor also exhibited high selectivity, stability and reproducibility when tested with clinical serum samples, highlighting its potential applications for early diagnosis and clinical monitoring.

Portable paper-based sheet for visual detection of ethyl carbamate in Chinese Baijiu based on aptamer recognition and laccase-like activity of cubic Ag2O nanoparticles

Ethyl carbamate (EC) is a small compound produced and stored during fermentation processes from ethanol, urea, citrulline, and carbamoyl phosphate. EC is commonly found in fermented foods and alcoholic beverages. Prolonged exposure to EC can cause nervous system diseases and liver damage in human beings. EC lacks stable physicochemical properties, and the presence of numerous interfering substances in alcoholic beverages poses challenges for its detection. Herein, it is found that EC1-34 aptamer bound to EC can enhance the laccase-like activity of cubic Ag2O nanoparticles (NPs). Subsequently, Ag2O NPs are wrapped with EC1-34 aptamer to prepare recognition probes, which are immobilized on a carrier membrane. Thus, a portable paper-based sheet for EC detection in Chinese Baijiu is designed. The visual detection limit of the developed paper-based sheet for EC is 10 μg⋅L-1, and shows an outstanding linear relationship within the range of 10-200 μg⋅L-1. Moreover, this colorimetric paper-based sheet has a good practicality in various Chinese Baijiu samples. It is believed that such paper-based sheet can facilitate portable inspection for EC in Baijiu, and may also become a beneficial tool for monitoring EC molecules in other fermented foods.

Accurate HER2 determination in breast cancer: a prominent COF-immobilized enzyme-enhanced electrochemical aptasensor employing 4-acetamidophenol as an efficient mediator

An effective strategy for enzyme-enhanced electrochemical detection of human epidermal growth factor receptor 2 (HER2) is proposed for breast cancer diagnosis. This strategy utilizes a three-dimensional mesoporous covalent organic framework (COF), immobilized horseradish peroxidase (HRP), and a novel redox mediator, 4-acetamidophenol (APAP). The mesoporous structure, with encapsulation effect, and good biocompatibility of COF, makes the functionalized COF an efficient carrier for HRP immobilization (HRP-Ab-AuNPs@COF). It demonstrates superior catalytic activity, stability, and electrochemical performance compared to free HRP, thus making it an ideal probe for simultaneous target recognition and signal amplification. APAP is screened from four candidate phenolic compounds based on its high formal potential (0.32 V vs. Ag/AgCl), rapid electron transfer activity (kapp = 2.80 × 105 M− 1 s− 1), excellent solubility and stability. These properties prove significantly better than the conventional mediator hydroquinone (HQ), achieving a higher signal-to-background ratio. By integrating decorated multi-walled carbon nanotubes as substrate materials, the electrochemical aptasensor achieves a low HER2 detection limit (0.418 pg mL− 1) with high specificity. This method’s selectivity surpasses that of the HQ-mediated method by 59–73%. Moreover, the aptasensor can effectively distinguish breast cancer patients and healthy individuals, as well as patients at different stages of the disease with high accuracy (AUC = 0.928). This performance exceeds traditional biomarkers CEA and CA15-3. This work paves novel avenues for innovative applications of COF-immobilized enzymes and the novel mediator APAP in electrochemical biosensing, thus holding significant promise for individualized breast cancer diagnosis and treatment.

DNA Aptamer-based Sensitive Electrochemical Biosensor for NAD(H) Detection

Nicotinamide-adenine dinucleotide (NAD(H)) plays a critical role in cellular metabolism, and its accurate measurement is essential for elucidating biological mechanisms and disease progression. However, specific recognition probes and sensitive biosensors for NAD(H) remains a significant challenge. Here, we screen an aptamer (NAD3-1a) that exhibits specific binding to NAD(H) with micromolar affinity. By incorporating this aptamer with tetrahedral DNA nanostructure, we develop a highly selective and sensitive electrochemical biosensor for the detection of NAD(H). This biosensor enables precise detection of NAD(H) within a linear range of 10-12∼10-7 M, offering remarkable stability and reproducibility. Utilizing this biosensor, we observed significant variations in the NAD(H) levels between normal and tumor cells, as well as a notable reduction in NAD(H) in the skeletal muscle tissues of aged mice. These results highlight the potential of this aptamer-based biosensor to advance our understanding of metabolic variations in both health and disease contexts.

Endogenous Telomerase-Activated Fluorescent Probes for Specific Detection and Imaging of Flap Endonuclease 1 in Cancer Cells and Tissues.

Flap endonuclease 1 (FEN1) is a structure-specific DNA repair enzyme that has emerged as a potential target for cancer diagnosis and treatment. However, existing FEN1 assays often suffer from complicated reaction schemes and laborious procedures, and only a few methods are available for the detection and imaging of FEN1 in living cells. Especially, FEN1 is not exclusive to cancer cells, but it is also shared by normal cells. Consequently, the specific detection of FEN1 in cancer cells remains a challenge. Herein, we develop a simple and selective fluorescent biosensor for the specific imaging of FEN1 in cancer cells and tissues by engineering a FEN1 detection probe with a telomerase-responsive unit. In the presence of telomerase, it induces an extension reaction and subsequent intramolecular reconfiguration of the detection probe, generating a suitable branched DNA structure for FEN1 recognition and facilitating the cleavage of the flap by FEN1 for the recovery of fluorescence signal. Because telomerase is undetectable in normal cells but highly upregulated in cancer cells, the detection probe can only be activated in cancer cells to generate a high signal. This assay is quite simple, with the requirement of merely a single probe for dual enzyme recognition and signal output. With the integration of the single-molecule counting technology, this biosensor can achieve a detection limit of 1.2 × 10-5 U/μL, and it can accurately detect FEN1 in living cells and clinical tissues, providing a new avenue for FEN1-associated fundamental research and clinical diagnosis.

Organic Circularly Polarized Room-Temperature Phosphorescence: Strategies, Applications and Challenges.

Organic circularly polarized luminescence (CPL) plays crucial roles in chemistry and biology for the potential in chiral recognition, asymmetric catalysis, 3D displays, and biological probes. The long-lived luminescence, large Stokes shift, and unique chiroptical properties make organic circularly polarized room-temperature phosphorescence (CPP) a new research hotspot in recent years. Nevertheless, achieving high-performance organic CPP is still challenging due to the sensitivity and complexity of integrating triplet excitons and polarization within organic materials. This review summarizes the latest advances in organic CPP, ranging from design strategies and photophysical properties to underlying luminescence mechanisms and potential applications. Specifically, the design strategies for generating CPP are systemically categorized and discussed according to the interactions between chiral units and chromophores. The applications of organic CPP in organic light-emitting diodes, sensing, chiral recognition, afterglow displays, and information encryption are also illustrated. In addition, we present the current challenges and perspectives on developing organic CPP. We expect this review to provide some instructive design principles to fabricate high-performance organic CPP materials, offering an in-depth understanding of the luminescence mechanism and paving the way toward diverse practical applications.

Organic Circularly Polarized Room‐Temperature Phosphorescence: Strategies, Applications and Challenges

AbstractOrganic circularly polarized luminescence (CPL) plays crucial roles in chemistry and biology for the potential in chiral recognition, asymmetric catalysis, 3D displays, and biological probes. The long‐lived luminescence, large Stokes shift, and unique chiroptical properties make organic circularly polarized room‐temperature phosphorescence (CPP) a new research hotspot in recent years. Nevertheless, achieving high‐performance organic CPP is still challenging due to the sensitivity and complexity of integrating triplet excitons and polarization within organic materials. This review summarizes the latest advances in organic CPP, ranging from design strategies and photophysical properties to underlying luminescence mechanisms and potential applications. Specifically, the design strategies for generating CPP are systemically categorized and discussed according to the interactions between chiral units and chromophores. The applications of organic CPP in organic light‐emitting diodes, sensing, chiral recognition, afterglow displays, and information encryption are also illustrated. In addition, we present the current challenges and perspectives on developing organic CPP. We expect this review to provide some instructive design principles to fabricate high‐performance organic CPP materials, offering an in‐depth understanding of the luminescence mechanism and paving the way toward diverse practical applications.

A novel electrochemiluminescent cytosensor using dual-target magnetic probe recognition and nanozymes-catalyzed cascade signal amplification for precise phenotypic enumeration of CTCs.

The inability of surgical biopsy to monitor the dynamic evolution of cancer cells hampers its capacity to reflect real-time tumor heterogeneity. Circulating tumor cells (CTCs), as a crucial target in liquid biopsy, offer a novel approach for accurate monitoring of tumors. However, the rarity and complex phenotype resulting from epithelial-mesenchymal transition pose challenges for conventional methods such as CellSearch and immunohistochemistry, which have insufficient ability for simultaneous phenotyping and enumeration of CTCs. The enumeration of a single phenotype CTCs is insufficient for accurately assessing disease progression. Herein, we propose a strategy to address this issue by fabricating an electrochemiluminescence cytosensor via the integration of dual-target enrichment and nanozymes-catalyzed cascade signal amplification. The graphene oxide@hollow mesoporous Prussian blue/Pt (GO@HMPB/Pt) complex, possessing a large specific surface area and exceptional catalytic activity, is employed for loading a substantial amount of luminol as the signal probe. Dual-target magnetic PPy@Fe3O4/Au-antibody/aptamer is utilized for the magnetic capture of both epithelial and interstitial CTCs. Glutathione (GSH) can disrupt theAu-S bond on aptamer by a thiol exchange reaction and selectively releases a specific subset of phenotypic CTCs, thereby facilitating the efficient capture, accurate classification, and ultrasensitive detection of CTCs in peripheral blood. Using the epithelial MCF-7 and mesenchymal Hela cells as models, the ECL cytosensor demonstrates excellent performance in identifying cells spiked into whole blood. This study presents a novel approach for early detection of metastasis, tracking tumor recurrence, and monitoring therapeutic efficacy.

A cyanobiphenol-based fluorescent probe for simultaneous recognition of Al3+ and Zn2+ and its application

A facile cyanobiphenol based probe MHB was synthesized and determined by FT-IR, 1H NMR, 13C NMR, HRMS and X-ray Crystallography. The probe MHB exhibited fluorescence turn-on phenomenon accompany with obvious color change from dark bule to azure and blue-green upon the addition of Al3+ and Zn2+, respectively. The binding ratios between probe MHB and Al3+/Zn2+ was 1:1 determined by Job’s plot, which was deeply investigated by FT-IR spectrum, 1HNMR titration and HRMS analysis. The detection limits of MHB to Al3+ and Zn2+ were 2.52 × 10−7 M and 1.74 × 10−7 M for Zn2+, respectively. The application experiments referring to real water samples, test paper and cell image showed that MHB was capable of qualitative and quantitative sensing Al3+/Zn2+ in environmental and biological system.

Ionic polymers as double-capture agents in an aptamer lateral flow assay strip for point-of-care detection of ethyl carbamate using peroxidase-like activity of bimetallic NiCo2O4 nanoparticles

A novel aptamer LFA (Apt-LFA) strip is first constructed for ethyl carbamate (EC) detection, in which cationic polyethyleneimine (PEI) and anionic polyacrylamide (APAM) are used as double-capture agents. The black NiCo2O4 nanoparticles (NCO NPs) encapsulated by EC1-34 aptamer are employed as recognition probes. The added EC will bind to EC1-34 aptamer on the probes, so that the test-line (T-line) immobilized with APAM can electrostatically capture the exposed NCO NPs. The control-line (C-line) sprayed with PEI can capture the excessive black recognition probes. The peroxidase-like activity of bimetallic NCO NPs is employed as signal amplification to improve the sensitivity of Apt-LFA strip. The naked eye discernible concentration of EC is 5 μg L−1 and the detection limit (LOD) is as low as 1.36 μg L−1. The Apt-LFA strip has the advantages of strong stability, simplicity and low cost, which provide a new method for EC detection and offer a new way for designing LFA.

Dual Recognition Strategy‐Based Transistor Sensor Array for Ultrasensitive and Multi‐Target Detection of Antibiotics

AbstractMulti‐target detection is a notable development direction in the field of analytical methods, boasting significant potential for breakthroughs in complex sample detection. Herein, an extended gate field‐effect transistor (EGFET) sensor array for ultrasensitive and multi‐target detection of antibiotics is developed. To enhance the recognition ability for diverse antibiotics, a dual‐recognition strategy based on tailor‐made molecularly imprinted polymer (MIP) and aptamer is adopted to fabricate the extended gate electrode (sensing electrode). The dual‐recognition strategy‐based EGFET exhibits superior sensitivity, selectivity, and stability compared to single recognition probes due to the synergistic effect of the affinities of MIP and specific aptamer. The developed sensor array can detect three types of antibiotics, including ampicillin, amoxicillin, and kanamycin, at the same time with record‐low detection limit (fM level) and a detection range spanning six orders of magnitude. The practical detection of antibiotics in various samples (tap water, river water, milk, honey, and artificial urine) further validates the feasibility of the sensor array in practical applications. The key advantages of flexibility, high sensitivity and selectivity, and multifunctionality demonstrate the high potential of EGFET sensor array for simultaneous detection of multiple target molecules.

Pattern recognition-based aptasensor array for discrimination of matrix effect

Nucleic acid aptamers have attracted considerable attention in recent years, particularly in the fields of disease diagnosis and treatment and biosensing. However, complex matrix effects have severely hindered their progress towards practical application. In this study, the novel strategy of a pattern recognition-based aptasensor array was introduced for target recognition based on the predictable selectivity capability of aptamers by circumventing the challenge of the interference of the matrix effect. As one proof of concept, we chose lactoferrin as the target protein, three selected aptamers with differential affinity as its recognition probes, eleven matrix samples of milk powder as the pattern discrimination model, and AuNPs color as the response signals. In the AuNPs colorimetric arrays, the lactoferrin-added milk powder matrix induced different degrees of protection on the surface of AuNPs particles due to different degrees of binding of lactoferrin to the three aptamer sequences and therefore exhibited differentiated red-to-blue color change along with salt-induced aggregation behaviors. The difference in color responses exhibited with and without lactoferrin addition was considered as the fingerprint pattern of the lactoferrin in each milk powder matrix, followed by the supervised machine learning analysis of linear discriminant analysis (LDA) for better orthogonality to complete the identification and prediction of the unknown samples. By this strategy, eleven kinds of milk powder at the added concentration of lactoferrin (50 nmol/L) presented a distinct response pattern and have been identified and classified with accuracies of 100 % via LDA patterns (three aptamers × eleven milk powder matrices × five replicates) with three canonical factors (91.2 %, 8.58 %, and 0.22 %). Furthermore, the accuracy of 22 unknown samples was 100 %, indicating the achievement in differentiating between different milk powder matrices and the identification of each matrix. The proposed aptasensor array complements the traditional “lock-and-key” single aptasensor and opens a new direction for developing sensitive sensing array systems circumventing complex matrix effects.

Chitosan-naphthalimide probes for dual channel recognition of HClO and H2S in cells and their application in photodynamic therapy

The combination of bio-imaging with photodynamic therapy (PDT) to accomplish theranostics is promising in cancer treatment. Three chitosan-naphthalimide probes were studied in this work. 4-(5-Bromothiophen-2-yl)-1,8-naphthalic anhydride was first synthesized, and then reacted with chitosan to obtain the macromolecules (CS-N-Br). The recognition group thiomorpholine or its derivatives were introduced into CS-N-Br to obtain nano-probes (CS-N-ML, CS-N-BSZ, CS-N-FSQ) eventually. The studies revealed that CS-N-ML and CS-N-FSQ exhibit high selectivity and can specifically recognize HClO and H2S. CS-N-ML and CS-N-FSQ can perform exogenous and endogenous confocal imaging of HClO and H2S in cells also. CS-N-ML's ability to target lysosomes positions indicated it could act as a lysosome-specific probe. It was discovered that the probes generate superoxide anions (O2•−) via a Type I mechanism. This discovery endows the probes with high photosensitizing activity even under hypoxic conditions. There is a positive correlation between the extent of the conjugated system and the photosensitivity of the probes, indicating that an enhanced conjugation leads to increased photosensitivity. Upon light irradiation, the probes generate ROS within HeLa cells. These results suggested that these probes can achieve theranostics for diseases associated with abnormal levels of HClO and H2S.

Recognition of MCF-7 breast cancer cells using native collagen probes: Collagen source effect

Developing superior cancer cell recognition probes is crucial for the development of tumor therapy and cancer early screening materials. In this study, we first achieved effective recognition of MCF-7 breast cancer cells using natural collagen probes. Through cell adhesion, cancer cell selective capture, and flow cytometry techniques, the binding efficiency of mammalian-derived collagens (bovine Achilles tendon collagen, porcine skin collagen) and fish-derived collagens (turbot skin collagen, grass carp skin collagen, mandarin fish skin collagen) to cancer cells (MCF-7 breast cancer cells) and normal cells (human umbilical vein endothelial cells, HUVECs) was analyzed and compared. The feasibility of different source collagens as probes for recognition of MCF-7 cells was explored in vitro. The results indicated that mammalian-derived collagens had a superior advantage over fish-derived collagens in recognizing MCF-7 cells, with bovine Achilles tendon collagen achieving a capture rate of up to 64.7 % in a multicellular co-culture system. Furthermore, in vivo imaging of BALB/c tumor-bearing mice confirmed the high-efficiency targeted recognition performance of the bovine Achilles tendon collagen probe for MCF-7 cells.

Enhanced SERS detection of the colorectal cancer biomarker utilizing a two-dimensional silver substrate

To improve the sensitivity, accuracy and specificity of the assay, a two-dimensional silver substrate with EF=5.85×108 was first synthesized as a SERS substrate, on the surface of which DSP molecules were modified to form a DSP-antibody coupling through the activation of two N-hydroxy succinimide (NHS) esters to capture TNF-α. Subsequently, aptamerized silver-coated gold nanospheres (Au@TFMBA@Ag) were synthesized as Surface-Enhanced Raman Scattering (SERS) recognition probes. These probes were employed to create a sandwich structure for the quantitative detection of Tumor Necrosis Factor-alpha (TNF-α), utilizing the SERS signal intensity at 1374 cm−1. Quantitative detection of TNF-α was successfully accomplished within the concentration range of 10−4 to 10−10 mg·mL−1. Clinical serum samples were collected and subjected to testing. Significance analysis, conducted through the T-test (p < 0.0001), unequivocally showed the method's ability to differentiate between sera from normal individuals and those diagnosed with colon cancer.

Z-scheme heterostructure of ZnO@NPC/Au/ZnIn2S4 for chemical replacement reaction-mediated signal-on photoelectrochemical assay of mercury ion

Herein, an advanced Zn-based metal organic framework (Zn-MOF) derived ZnO embedded in a nitrogen-doped porous carbon (ZnO@NPC) polyhedron/Au/ three-dimensional (3D) chrysanthemum-like ZnIn2S Z-scheme heterojunction was employed for the chemical replacement reaction-mediated signal-on photoelectrochemical (PEC) sensing detection of mercury ions (Hg2+). The p-type ZnO@NPC polyhedron was initially prepared by carbonising the zeolitic imidazolate framework (ZIF)-8 polyhedron, followed by modification with Au nanoparticles (NPs) via an in situ photocatalytic reduction method. Subsequently, the ZnO@NPC/Au polyhedron was combined with n-type 3D chrysanthemum-like ZnIn2S4 through physical adsorption, forming the ZnO@NPC polyhedron/Au/3D chrysanthemum-like ZnIn2S4 Z-scheme heterostructure. The newly constructed heterostructure exhibited strong visible light–harvesting capacity, and considerably improved photoelectric conversion efficiency. The 3D chrysanthemum-like ZnIn2S4 functioned not only as a photosensitiser but also as an Hg2+ recognition probe. Importantly, the PEC sensor exhibited a considerably increased photocurrent response to Hg2+. This is presumably because the introduction of Hg2+ triggered a selective Zn-to-Hg chemical replacement reaction, leading to the in-situ formation of a ZnO@NPC/Au/ZnIn2S4/HgS heterojunction, which further improved charge separation. Consequently, Hg2+ was sensitively detected with a wide linear range from 0.5 pM to 2 μM and a low detection limit of 0.07 pM. Furthermore, the proposed sensor was validated by detecting Hg2+ in food and aqueous environments, indicating its potential application in food safety and environmental monitoring.

Highly sensitive β-amyloid1–42 oligomer aptamer-based assay via dual cyclic amplifications of three-way catalytic hairpin assembly and palindrome polymerase reaction

β-amyloid1–42 oligomer (AβO1–42), a neurotoxic protein, is considered the key factor in the progression of Alzheimer's disease (AD). And, high sensitivity detection of AβO1–42 is of considerable importance for the early diagnosis and deterioration prevention of AD. We present here an ultrasensitive fluorescent AβO1–42 detection approach based on aptamer recognition probes and a new dual cyclic signal amplification strategy by combining three-way catalytic hairpin assembly (3W-CHA) with palindromic sequence-based polymerase amplification (PBPA). Once the aptamers bind to target AβO1–42 molecules, ssDNA sequences are released to initiate 3W-CHA between three hairpins to unfold the signal hairpins and to form Y-shaped DNA structures (Y-DNAs). Subsequently, the assistance ssDNAs bind the Y-DNAs to expose the palindromic sequences to yield Y-DNA dimers, which lead to cyclic PBPA reaction with presence of polymerase to further unfold more signal hairpins for yielding considerably magnified fluorescence recovery, enabling sensitive assay of AβO1–42 down to 2.4 pM within a dynamic range of 5 pM∼50 nM. Furthermore, this strategy has been validated for interrogation of low AβO1–42 levels in artificial cerebrospinal fluid (CSF), suggesting its promising potential for application in early diagnosis and prevention of AD.