Specific Recognition Of Aptamer Research Articles

Insulin‐like Growth Factor 2‐Tagged Aptamer Chimeras (ITACs) Modular Assembly for Targeted and Efficient Degradation of Two Membrane Proteins

AbstractOverexpression of pathogenic membrane proteins drives abnormal proliferation and invasion of tumor cells. Various strategies to durably knockdown membrane proteins with heterobifunctional degraders have been successfully developed, including LYTAC, KineTAC, and AbTAC. However, challenges including complicated synthetic procedures and the inability to simultaneously degrade multiple pathogenic proteins still exist. Herein, we developed insulin‐like growth factor 2 (IGF2)‐tagged aptamer chimeras (ITACs) that link the cell‐surface lysosome‐targeting receptor IGF2R and membrane proteins of interest (POIs) based on specific recognition of aptamers to the POIs and high‐affinity binding of IGF2 to IGF2R. We demonstrated that ITACs exhibit robust degradation efficiency of various membrane proteins in multiple cell lines. Furthermore, systematic studies revealed that a moderate cell‐surface IGF2R level is responsible for the excellent degradation performance of ITACs. Importantly, we further established a modular assembly strategy that allows assembly of one IGF2 with two aptamers with precise stoichiometry (dITACs), enabling cooperative and simultaneous degradation of two membrane proteins. This work provides an efficient and facile target membrane protein degradation platform and will shed light on the treatment of diseases related to the overexpression of membrane proteins.

Insulin-like Growth Factor 2-Tagged Aptamer Chimeras (ITACs) Modular Assembly for Targeted and Efficient Degradation of Two Membrane Proteins.

Overexpression of pathogenic membrane proteins drives abnormal proliferation and invasion of tumor cells. Various strategies to durably knockdown membrane proteins with heterobifunctional degraders have been successfully developed, including LYTAC, KineTAC, and AbTAC. However, challenges including complicated synthetic procedures and the inability to simultaneously degrade multiple pathogenic proteins still exist. Herein, we developed insulin-like growth factor 2 (IGF2)-tagged aptamer chimeras (ITACs) that link the cell-surface lysosome-targeting receptor IGF2R and membrane proteins of interest (POIs) based on specific recognition of aptamers to the POIs and high-affinity binding of IGF2 to IGF2R. We demonstrated that ITACs exhibit robust degradation efficiency of various membrane proteins in multiple cell lines. Furthermore, systematic studies revealed that a moderate cell-surface IGF2R level is responsible for the excellent degradation performance of ITACs. Importantly, we further established a modular assembly strategy that allows assembly of one IGF2 with two aptamers with precise stoichiometry (dITACs), enabling cooperative and simultaneous degradation of two membrane proteins. This work provides an efficient and facile target membrane protein degradation platform and will shed light on the treatment of diseases related to the overexpression of membrane proteins.

NIR-II excitation self-assembly nanomedicine for targeted NIR-IIa fluorescence imaging-guided cuproptosis-promoted synergistic therapy against triple-negative breast cancer

Owing to easy copper efflux, the deficiency of targeting delivery and limited tissue penetration depth of light, the combination therapy of cuproptosis and phototheranostics remains enormous challenges towards triple-negative breast cancer (TNBC). To overcome these obstacles, a NIR-II excitation multifunctional nanomedicine is prepared by self-assembly of targeting aptamers (AS1411) utilizes metallic copper ions as coordination nodes, followed by coated with ultrasmall NIR-II polymer dots (Pdots) with excellent optical performances, forming a carrier-free hybrid nanosystem. After positive targeting into TNBC through specific recognition of aptamer towards cell surface nucleolin, Pdots loaded in nanomedicine enable NIR-IIa fluorescence/NIR-II photoacoustic imaging-guided NIR-II photothermal therapy (PTT) under NIR-II (1064 nm) light excitation, achieving precise phototheranostics of TNBC tumors. The loaded Cu(II) is reduced to cytotoxic Cu(I) by intracellular glutathione (GSH) and ferredoxin 1 (FDX1), synchronously enabling chemodynamic therapy (CDT) and inducing cuproptosis against TNBC. NIR-II PTT and GSH depletion further enhance therapeutic efficiency of CDT and cuprptosis through cell sensitization. This work provides a new attempt to integrate NIR-II phototheranostics and cuproptosis into a single nanoplatform with targeting capability for synergistic therapy of TNBC.

Tetrahedral DNA nanostructure enhanced toehold-mediated strand displacement for highly sensitive electrochemiluminescence assay of CA125

Cancer antigen 125 (CA125) is a typical tumor marker of ovarian cancer. Here, a multi-amplified electrochemiluminescence (ECL) aptasensor was developed for efficient recognition of CA125 using tetrahedral DNA nanostructure (TDN) enhanced toehold-mediated strand displacement (TMSD) coupled with gold nanoparticles/Ru(bpy)32+/metal–organic framework (AuNPs/Ru/ZIF-MOF) signal probe. AuNPs and Ru(bpy)32+ modified ZIF-MOF acted as initial ECL signal and further used for the immobilization of TDN, the activated DNA templates on the surface of TDN were firstly hybridized with ferrocene labeled DNA probe (S6) and S5, in which, S6 acted as the energy acceptor of ECL signal from Ru(bpy)32+, making the sensor in a “signal-off” state. After the specific recognition of aptamer (AP) with CA125, DNA initiator (S7) was freed to induce the happen of TMSD by using S8 as the helper DNA, accompanying with the release of S6 from the electrode surface and the recovery of Ru(bpy)32+ ECL signal, making the sensor in a “signal-on” state. Then, S7 was recycled for the next TMSD, making the sensor highly sensitive with a detection limit of 6 × 10-3 pg/mL. Moreover, the proposed aptasensor achieved high performance for CA125 detection in human serum samples, illustrating the reliability of the sensor in clinical analysis.

Surfactant-mediated colorimetric assay assisted with in-situ rolling circle amplification on magnetic beads

Gold nanoparticles (AuNPs) with localized surface plasmon resonance effect have been widely used for colorimetric detection based on the interparticle plasmon coupling during AuNPs aggregation. However, it is still challenging to develop portable and quantitative methods with good sensitivity and excellent selectivity. In this study, a smartphone-based colorimetric assay is developed on the principle of surfactant-mediated AuNPs aggregation assisted with rolling circle amplification (RCA) on magnetic beads (MBs). The detection of adenosine is demonstrated as an example. The cetyl trimethyl ammonium bromide (CTAB) causes the negatively charged AuNPs to aggregate, which results in the color change from red to blue. When adenosine is in solution, the RCA process is triggered on the MBs because of specific adenosine-aptamer recognition, resulting in prolongation of single-stranded nucleic acid (ssDNA). The solution color remains red due to the electrostatic interaction between CTAB and ssDNA. Using this method, the limit of detection (LOD) for adenosine can be as low as 16 pM. Besides, it also works well in human serum. In addition, a portable device integrated with in-situ RGB analysis software is developed for the detection with a smartphone. This study offers a new strategy to improve the sensitivity and selectivity for the AuNPs-based colorimetric assay, taking advantages of specific aptamer recognition, in-situ RCA on MBs, magnetic separation, and smartphone-based portable device.

Establishment of a photoactive heterojunction of triazine covalent-organic polymer and copper (II) selenide: Photoelectrochemical aptasensing strategy for efficiently detecting Salmonella typhimurium

The sensitive determination of foodborne pathogens in foodstuffs or water system is essential for protecting food and environment safety. Herein, we have proposed a photoelectrochemical (PEC) aptasensor based on two-dimensional (2D)/3D organic–inorganic heterojunction for the efficient detection of Salmonella typhimurium (S. typhimurium). The heterojunction was established via the in situ growth of copper (II) selenide (CuSe) nanosheets around the photoactive triazine covalent-organic polymer (COP) nanospheres, which was synthesized using 2,4,6-Tris(4-aminophenyl)-1,3,5-Triazine (TAPT) and 2,4,6-trihydroxy-1,3,5-benzenetricarbaldehyde (Tp) as building blocks (denoted as TAPT-Tp-COP@CuSe). Integrating the features of TAPT-Tp-COP (such as large specific surface and pore size, multi-functionality, and rich defects) and CuSe (such as high photoabsorption ability, fast electron transfer and effective separation of the photo-generated charge carrier) not only can accelerate the photoelectric transformation efficiency, but also can promote the aptamer immobilization. Consequently, the constructed PEC aptasensor based on TAPT-Tp-COP@CuSe illustrated a low detection limit of 3.4 CFU mL−1 with a linear range from 1 × 101 to 1 × 105 CFU mL−1 toward S. typhimurium. In addition, it demonstrated high selectivity in light of the specific recognition of aptamer toward S. typhimurium, good reproducibility and stability, and promising regeneration ability, as well as wide applications for the detection of S. typhimurium in diverse foodstuffs systems. The present work provides a new aptasensing strategy for the effective detection of foodborne pathogens from diverse foodstuffs by combining the merits of COPs and PEC technique.

Ratiometric SERS aptasensing for simultaneous quantitative detection of histamine and tyramine in fishes

Herein, a SiO2@Ag NPs core/shell nanoparticles were synthesized to fabricate a surface-enhanced Raman spectroscopy (SERS) sensor for the simultaneous determination of histamine (HIS) and tyramine (TYR) based on specific aptamer recognition and ratiometric strategy. SiO2@Ag NPs with 4-thiosaminophenol (4-ATP) and Nile blue A (NBA) molecules were used as an internal standard (IS) and labeled with aptamers corresponding to HIS and TYR, respectively. Raman reporter molecules ROX and Cy5 labeled complementary DNA (cDNA) were then hybridized with aptamers to form rigid double-stranded DNA. After the HIS and TYR were captured by their aptamers, resulting in the dissociation of cDNA and separated from the SERS substrate. Therefore, the SERS signal intensity at 1503 cm−1 of ROX and 1358 cm−1 of Cy5 tagged on the terminal of cDNA decreased with the concentration of HIS and TYR increasing, while the SERS signal intensity at 1079 cm−1 of 4-APT and 592 cm−1 of NBA on the substrate remain stable. Thus, the concentrations of HIS and TYR can be determined by the I1503/I1079 and I1358/I592 values, respectively. This sensing strategy achieves a lower detection limit of 0.2 ng/mL for HIS and 0.05 ng/mL for TYR, respectively, demonstrating promising applications in sensitive detection of BAs in animal-derived foodstuff.

Efficient photoelectrochemical aptasensing of di-2-ethylhexyl phthalate in environmental samples based on N, S co-doped graphene quantum dots/TiO2 nanorods

An efficient photoelectrochemical (PEC) sensing platform was developed for detection of di-2-ethylhexyl phthalate (DEHP) based on nitrogen and sulfur co-doped graphene quantum dots/TiO2 nanorods (N, S-GQDs/TiO2 NRs) coupling with exonuclease I (Exo I)-assisted target recycling for remarkable signal amplification. N, S-GQDs uniformly grown on TiO2 NRs by simple hydrothermal method showed high electron-hole separation efficiency and superior photoelectric performance, which was explored as the photoactive substrate for anchoring anti-DEHP aptamer and its complementary DNA (cDNA). With the addition of DEHP, aptamer molecules fell from the electrode surface owing to the specific recognition of aptamer to DEHP, resulting in the increment of photocurrent signal. At this moment, Exo I could stimulate aptamer hydrolysis in the aptamer-DEHP complexes, so that DEHP was released from the complexes to take part in the next reaction cycling, which remarkably increasing the photocurrent response and achieving signal amplification. The designed PEC sensing platform exhibited excellent analytical performance for DEHP with a low detection limit of 0.1 pg L−1. Also, its applications in real samples were further investigated in detail. Thus, the established method would provide a simple and efficient tool for DEHP or other pollutants monitoring in the environment.

A novel acetylcholinesterase regulated upconversion-FITC fluorescence aptasensor for supersensitive detection of sulfadiazine in aquatic products

In this study, a novel fluorescence aptasensor was designed for the detection of sulfadiazine (SDZ) based on the pH-sensitive strategy to improve the fluorescence resonance energy transfer (FRET) efficiency. Acetylcholinesterase (AChE) was employed to regulated microenvironment responsiveness of the FRET between upconversion nanoparticles (UCNPs) as donors and pH-sensitive fluorescein isothiocyanate (FITC) dye as the effective acceptor. An energy transfer effect resulted in FITC strongly quenched the fluorescence of UCNPs. Upon addition of acetylthiocholine (ACh) and cDNA-modified AChE (cDNA-AChE), cDNA-AChE was assembled with aptamer functionalized FITC-modified UCNPs (UCNPs-FITC-aptamer), and the product of catalytic hydrolysis (acetic acid) changed the pH of the microenvironment surrounding UCNPs, causing the quenched fluorescence restored. The specific recognition of aptamer to SDZ broke the assembly composition, and reduced the recovery of fluorescence response signal. The linear relationship was achieved over the concentration range from 0.1 to 100 ng/mL and the limit of detection (LOD) was 0.031 ng/mL. In addition, the developed biosensor exhibited satisfactory results with (p > 0.05) enzyme-linked immunosorbent assay (ELISA). The excellent performance of the proposed biosensor confirmed the enormous potential to detect SDZ residuals in aquatic products.

Encoded Structural Color Microneedle Patches for Multiple Screening of Wound Small Molecules.

Detection of biomarkers associated with wound conditions provides in-depth healthcare information and benefits wound healing treatment. The current aim of wound detection is to achieve in situ multiple detection. Here, we describe novel encoded structural color microneedle patches (EMNs) combining photonic crystals (PhCs) and microneedle arrays (MNs) for multiple wound biomarker detection in situ. Using a partitioned and layered casting strategy, the EMNs can be divided into different modules and each serves for the detection of small molecules associated with chronic hard-to-healing wounds, including pH, glucose and histamine. pH sensing is based on the interaction between hydrogen ions and carboxyl groups from hydrolyzed polyacrylamide (PAM); glucose sensing is achieved with the help of glucose-responsive fluorophenylboronic acid (FPBA); while histamine sensing relies on specific recognition of aptamers and target molecules. Owing to the responsive volume change of these three modules in the presence of target molecules, the EMNs can create structural color change and characteristic peak shift of the PhCs, thus realizing the qualitative measurement of target molecules with a spectrum analyzer. It is further demonstrated that the EMNs behave well in the multivariate detection of rat wound molecules. These features indicate that the EMNs can be valuable smart detection systems for wound status screening. This article is protected by copyright. All rights reserved.

Advanced Pt hollow nanospheres/rubrene nanoleaves coupled with M-shaped DNA walker for ultrasensitive electrochemiluminescence bioassay

Herein, an intense electrochemiluminescence (ECL) was achieved based on Pt hollow nanospheres/rubrene nanoleaves (Pt HNSs/Rub NLs) without the addition of any coreactant, which was employed for ultrasensitive detection of carcinoembryonic antigen (CEA) coupled with an M-shaped DNA walker (M-DNA walker) as signal switch. Specifically, in comparison with platinum nanoparticles (Pt NPs), Pt HNSs revealed excellent catalytic performance and pore confinement-enhanced ECL, which could significantly amplify ECL intensity of Rub NLs/dissolved O2 (DO) binary system. Then, the tracks and M-DNA walker were confined on the Pt HNSs simultaneously to promote the reaction efficiency, whose M-structure boosted the interaction sites between walking strands and tracks and reduced the rigidity of their recognition. Once the CEA approached the sensing interface, the M-DNA walker was activated based on highly specific aptamer recognition to recover ECL intensity with the assistance of exonuclease Ⅲ (Exo Ⅲ). As proof of concept, the “on-off-on” switch aptasensor was constructed for CEA detection with a low detection limit of 0.20 fg/mL. The principle of the constructed ECL aptasensor also enables a universal platform for sensitive detection of other tumor markers.

Terminal deoxynucleotidyl transferase associated with split G-quadruplex/hemin deoxyribozyme amplification detection for various contaminants in milk based on pregnancy test strip platform

Contaminant residue analysis in milk can provide essential assistance for safety quality and contamination level management of milk production, which is critical for safeguarding public health. In this study, the pregnancy test strip is employed to achieve multiple analytes detection based on the specific recognition of aptamer and terminal deoxynucleotidyl transferase associated with split G-quadruplex/hemin deoxyribozyme system. Through the subsequent enzyme catalyzed reaction, the detection signal can be further amplified to improve the sensitivity. The method does not need to assemble test strip, prepare and purify antibodies/haptens, nor design complex probe sequences. By coupling human chorionic gonadotrophin with DNA probes and combining magnetic separation technology, the targets can be determined via the test strip. Under the optimized conditions, the visual detection limits for mercury ion, bisphenol A, and penicillin are 1, 0.1 and 0.05 nM, respectively. The detection results show that the method displays good accuracy and practicability in spiked milk sample. The method presents a simple scheme, low cost as well as good design versatility, which demonstrates great application prospect for the sensitive, low-cost, and convenient detection of food matrices.

Aptamer-based sensor for specific recognition of malathion in fruits and vegetables by surface-enhanced Raman spectroscopy and electrochemistry combination

ABSTRACT: Aptamers are single-stranded DNA or RNA that can specifically bind to a target substance with high affinity. Pesticides have obvious biological effects and are very harmful to the human body and the environment. Surface-enhanced Raman spectroscopy (SERS) can be combined with aptamer for the rapid detection of pesticide residues because of its simple operation and high sensitivity. However, a single analysis method has certain limitations and can't satisfy the research of complex system. In this study, SERS and electrochemical were used to prove the specific recognition of malathion by aptamer. The biochemical sensor directly detected the SERS spectra of the aptamer, malathion, and aptamer-malathion through the SERS method. Malathion could also be verified the specific recognition of aptamer by differential pulse voltammetry (DPV) and cyclic voltammetry (CV). Based on the peak difference before and after the combination of malathion and aptamer, a detection method for the specific recognition of malathion in a complex system was established. The identification mechanism was discussed. Then, the practical detection of malathion demonstrated the practicability of the method. The method was applied for the detection of malathion in spiked apple and bell pepper samples. The recoveries were in the range of 89.80%–106.50%, and the relative standard deviations were from 2.51%–6.92%. The use of aptamers for the specific detection of pesticides will have the potential for broad applications in the future.

Electrochemical aptasensor based on Ce3NbO7/CeO2@Au hollow nanospheres by using Nb.BbvCI-triggered and bipedal DNA walker amplification strategy for zearalenone detection

Herein, an electrochemical aptasensor combining Nb.BbvCI-triggered bipedal DNA walking strategy was constructed for ultrasensitive assay of zearalenone (ZEN). The aptasensor used Ce3NbO7/CeO2 @Au hollow nanospheres as electrode modification material and PdNi@MnO2/MB as the signal label. Importantly, the Ce3NbO7/CeO2 synthesized by hydrothermal method were combined with Au nanoparticles and applied to the electrode surface. The as-prepared Ce3NbO7/CeO2 @Au possessed a large surface area, excellent electrical conductivity, stability and more binding sites. PdNi@MnO2 with high specific surface area and porosity combined with molecule methylene blue (MB) was introduced into electrodes as the signal label. The proposed aptasensor utilized the advantages of specific recognition of aptamers and target molecules to release bipedal DNA walker (w-DNA), and then the w-DNA was triggered by Nb.BbvCI and entered the cycle to release more signal probes. The feasibility of this strategy was recorded by the differential pulse voltammetry (DPV) method. Under the optimized conditions, the electrochemical aptasensor exhibited a wide linear dynamic range from 1 × 10−4 to 1 × 103 ng mL−1 with a low detection limit of 4.57 × 10–6 ng mL−1. Moreover, the aptasensor had high selectivity, good stability, excellent repeatability and provided an effective method for the trace detection of ZEN in real samples.

Integrated DNA triangular prism nanomachines for two-stage dynamic recognizing and bio-imaging from surface to the inside of living cells

The identification and detection of biomarkers in cancer cells play an essential role in the early detection of diseases, especially the detection of dual-biomarker. However, one of the most important limiting factors is how to realize the identification and labeling of biomarkers dynamically from the plasma membrane to the cytoplasm in living cells. In this study, integrated DNA triangular prism nanomachines (IDTPNs), a two-stage identification and dynamic bio-imaging strategy, recognize biomarkers from the plasma membrane to the cytoplasm have been designed. DNA triangular prism (DTP) was selected to act as a delivery platform with the aptamer Sgc8c and P53 modified on the side as the recognition molecules. Through the specific recognition of aptamers and the superior internalization of DTP, the IDTPNs realize the dynamic responses to PTK7 and p53 from the membrane to the cytoplasm in living cells. It is proved that the IDTPNs can be used for dynamic dual-biomarker recognition and bio-image from the surface to the inside of tumor cells automatically. Therefore, the strategy we developed provides a reliable platform for tumor diagnosis and biomarker research.

Amplification of fluorescence polarization signal based on specific recognition of aptamers combined with quantum quenching effect for ultrasensitive and simple detection of PCB-77

Here, we report a novel aptasensor based on decahedral silver nanoparticles (Ag10NPs) enhanced fluorescence polarization (FP) for detecting PCB-77. Using aptamer modified Ag10NPs hybridized with DNA sequence labeled fluorescent group as an analytical probe, polychlorinated biphenyls (PCB-77) could be detected with high sensitivity and selectivity. The linear range of determination was 0.02 ng/L to 390 ng/L and the limit of detection was 5 pg/L. In addition, through the optimization of the experiment condition and signal probe DNA (pDNA), we found that the maximum FP signal could be generated when the distance between fluorescein and the surface of Ag10NPs was 3 nm. When the aptamer was immobilized on the surface of Ag10NPs could be strengthened the anti-interference performance of aptamer nanoprobe and further improved the detection ability. At the same time, we also compared the detection performance of the traditional FP signal enhancer streptavidin (SA) analysis system. The fluorescence polarization aptasensor could detect PCB-77 samples efficiently in complex environmental water, which shows a good application prospect.

An Iron(III)-Based Metal-Organic Gel-Catalyzed Dual Electrochemiluminescence System for Cytosensing and In Situ Evaluation of the VEGF165 Subtype.

The recent surge of interest in metal-organic gels (MOGs) has emerged for their soft porous structure, large surface area, and abundant active metal sites, making them a promising candidate for building catalyst matrices. In this work, facilely synthesized Fe(III)-organic gel was directly used as a robust electrode matrix. Detailed studies illustrated that their Fe(III) centers can speed up the electro-oxidation/reduction of the H2O2 coreactant to produce reactive oxygen species for enhancing a potential-resolved dual electrochemiluminescence (ECL) emission. Among them, the anodic signal of luminol varied with the cell concentration based on the impedance ECL mechanism, while the cathodic signal of CdS quantum dots traced the VEGF165 subtype at cell surface by specific aptamer recognition. Based on this, a ratiometric strategy was proposed for accurate cytosensing by eliminating environmental interference. Moreover, by cooperating these two signals, a novel strategy was developed for direct evaluation of the VEGF165 subtype, further realizing rapid drug screening and subtype assessment on different cell lines. This work not only opens up the promising application of MOGs as an effective catalyst matrix but also develops reliable cell assays and protein subtype identification for clinical diagnosis and research.

Simple Design Concept for Dual-Channel Detection of Ochratoxin A Based on Bifunctional Metal-Organic Framework.

A simple fluorescence and electrochemical dual-channel biosensor based on bifunctional Zr(IV)-based metal-organic framework (Zr-MOF) was proposed to detect Ochratoxin A (OTA). The bifunctional Zr-MOF, with photoluminescence properties and enormous electroactive ligands, was exploited to load OTA-specific aptamers for designing signal probes, greatly simplifying the probe-fabrication process and improving sensing reliability. Upon specific recognition of aptamer toward OTA, the anchored probe was released from the sensing interface into the reaction solution. In this circumstance, the increased amount of the signal probe in reaction solution led to an enhanced fluorescence response, while the decreased amount of the signal probe on the sensing interface resulted in a diminished electrochemical response. According to the dual-channel signal change with increasing OTA concentration, the visual fluorescence strategy was established for intuitive OTA detection, and meanwhile, sensitive electrochemical assay with a detection limit of 0.024 pg/mL was also achieved with the help of one-step electrodeposition as a sensing platform. Moreover, the proposed dual-channel assay has been successfully applied to determine OTA levels in corn samples with rapid response, superior accuracy, and high anti-interference capability, providing a promising method for food safety monitoring.

Visual detection of aflatoxin B1 based on specific aptamer recognition combining with triple amplification strategy

A highly sensitive and specific visual detection method for aflatoxin B1 (AFB1) based on the target specificity of aptamer, rolling circle amplification (RCA) and enzyme catalysis biological amplification effect has been established. In this work, AFB1 aptamer immobilized on the surface of magnetic beads (MB) serves as a molecular recognition probe. In the absence of AFB1, the aptamer and auxiliary linking probe (LP) maintain a double stranded state due to partial base pair complementarities. By contrast, in the presence of AFB1, the aptamer preferentially binds to AFB1 specifically, and the LP later restores to a single stranded state. Subsequently, the RCA reaction is triggered by above-mentioned single stranded LP to generate long DNA strands, which are employed to capture amounts of signal probes (SP) and horse radish peroxidases (HRP). Finally, amounts of HRP catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) by H2O2 and leads to a dramatic color change of the solution from colorlessness to deep blue as a signal indicator, obtaining a high sensitivity, high specificity and visual detection of AFB1. Under optimal conditions, a good linear detection range (0.5–40 pg·mL−1) was achieved, and the limit of detection (LOD) was 0.13 pg·mL−1. Besides, the proposed aptasensor showed excellent specificity for AFB1 compared with five other mycotoxins. More than that, all reactions occur on the surface of the magnetic beads, which not only facilitates the detection operation process including the efficient isolation and collection of AFB1 from sample matrix, but also gets better selectivity and stronger resistibility to target analyte in complex sample matrix, adequately indicating its potential application in AFB1 practical detection.

Detection of multiple mycotoxins based on catalytic hairpin assembly coupled with pregnancy test strip

Various mycotoxins are widely present in crop products, which cause serious harm to human and animals. In this study, combining the specific recognition of aptamer with catalytic hairpin assembly (CHA) strategy, the pregnancy test strip is used to detect multiple mycotoxins. The signal amplification can be further achieved through following enzymatic reaction to increase sensitivity. In the experiment, there is no need to assemble test strip as well as prepare and purify antibody/hapten. It only requires to couple human chorionic gonadotropin (hCG) with DNA probe to realize the target determination via CHA process and enzymatic signal amplification on the test strip. Under optimal conditions, using the CHA based pregnancy test strip detection platform, the visual limits of detection for aflatoxin B1, ochratoxin and zearalenone can be obtained within 15 min, which are 20, 50 and 20 pg/mL, respectively. The detection results of the spiked samples show that the platform possesses satisfied accuracy, reproducibility and practicability. The method has facile scheme, low cost and good design versatility, and reveals potential application prospects in high sensitivity, low cost, and convenient detection of mycotoxins.