Differential Pulse Voltammetry Signal Research Articles

A fluorescence-electrochemical dual-mode aptasensor for ultrasensitive detection of lead based on exonuclease-catalyzed recycling and hybridization chain reaction amplification

To improve the accuracy and reliability of the detection system, this study combined the exonuclease-assisted autocatalytic target cycling fluorescence strategy with an electrochemical platform to establish a dual-mode fluorescence-electrochemical aptasensor for the ultra-sensitive quantification of lead ion (Pb2+). In the fluorescence detection strategy, ssDNA could hybridize with the aptamer to form double-stranded DNA. With the addition of Pb2+, the aptamer dissociated from the double-stranded DNA to capture Pb2+ and trigger the enzymatic digestion process, leading to the target recirculation to achieve the first signal amplification. The free ssDNA could then hybridize with S1, and the released S2 was able to trigger a hybridization chain reaction (HCR) in the electrochemical system, achieving the second signal amplification. The quantification of Pb2+ was realized by measuring both the fluorescence and the differential pulse voltammetry signals with detection limits of 0.028 ng/mL and 0.788 pg/mL, respectively. This fluorescence-electrochemical dual-mode aptasensor overcame the limitations of complex matrices and environmental interference, and provided a valuable reference for the development of reliable multi-signal sensors in water, tea and vegetable safety monitoring.

Intelligent machine learning enabled sensor for acyclovir using NiMnO3 flower-like electrocatalyst

Hierarchical flower-like NiMnO3 was prepared using a hydrothermal route for oxidative detection of acyclovir (ACV), an antiviral pharmaceutical pollutant. The flower-like structure with an electroactive surface area (EASA) of 0.0952 cm2 enables non-revisable oxidation of ACV, with differential pulse voltammetry (DPV) and amperometry confirming its robust analytical capability in both high (15–75 µM) and low (0.1–1.0 µM) concentration ranges, respectively. Using amperometry, the sensor achieved an estimated limit of detection (LOD) of 1.59 nM (S/N=3) with selective oxidation of ACV and a sensitivity of 1.039µA µM−1 cm2 in the presence of other common interferants. The adaptation of machine learning (ML) algorithms like random forest, XGBoost, linear regression, and ANN validated sensors’ performance and confirmed ANN’s superiority in DPV signal interpretation. NiMnO3, as an electrocatalyst for ACV oxidation, validated by ANN modeling, highlights bimetallic oxides’ potential as a cost-effective, versatile platform for detecting pharmaceutical pollutants.

Self-powered sensing platform for monitoring uric acid in sweat using cobalt nanocrystal-graphene quantum dot-Ti3C2TX monolithic film electrode with excellent supercapacitor and sensing behavior.

Thesynthesis of cobalt nanocrystal-graphene quantum dot-Ti3C2TX monolithic film electrode (Co-GQD-Ti3C2TX) is reportedvia self-assembly of Ti3C2TX nanosheets induced by protonated arginine-functionalized graphene quantum dot and subsequent reduction of cobalt (III). The resulting Co-GQD-Ti3C2TX shows good monolithic architecture, mechanical property, dispersibility and conductivity. The structure achieves excellent supercapacitor and sensing behavior. The self-charging supercapacitor produced by printing viscous Co-GQD-Ti3C2TX hydrogel on theback of flexible solar cell surfaceprovides high specific capacitance (296 F g-1 at 1 A g-1), high-rate capacity (153 F g-1 at 20 A g-1), capacity retention (98.1% over 10,000-cycle) and energy density (29.6 W h kg-1 at 299.9 W kg-1). The electrochemical chip produced by printing Co-GQD-Ti3C2TX hydrogel on paper exhibits sensitive electrochemical response towards uric acid. The increase of uric acid between 0.01 and 800μM causes a linear increase in differential pulse voltammetry signal with adetection limit of 0.0032μM. The self-powered sensing platform integrating self-charging supercapacitor, electrochemical chip and micro electrochemical workstation was contentedly applied to monitoring uric acid in sweats and shows one broad application prospect in wearable electronic health monitoring device.

Graphene oxide/Cu–MOF-based electrochemical immunosensor for the simultaneous detection of Mycoplasma pneumoniae and Legionella pneumophila antigens in water

The combination of copper–metal organic framework (Cu–MOF) with graphene oxide (GO) has received growing interest in electrocatalysis, energy storage and sensing applications. However, its potential as an electrochemical biosensing platform remains largely unexplored. In this study, we introduce the synthesis of GO/Cu–MOF nanocomposite and its application in the simultaneous detection of two biomarkers associated with lower respiratory infections, marking the first instance of its use in this capacity. The physicochemical properties and structural elucidation of this composite were studied with the support of XRD, FTIR, SEM and electrochemical techniques. The immunosensor was fabricated by drop casting the nanocomposite on dual screen-printed electrodes followed by functionalization with pyrene linker. The covalent immobilization of the monoclonal antibodies of the bacterial antigens of Mycoplasma pneumoniae (M. pneumoniae; M. p.) and Legionella pneumophila (L. pneumophila; L. p.) was achieved using EDC-NHS chemistry. The differential pulse voltammetry (DPV) signals of the developed immunosensor platform demonstrated a robust correlation across a broad concentration range from 1 pg/mL to 100 ng/mL. The immunosensor platform has shown high degree of selectivity against antigens for various respiratory pathogens. Moreover, the dual immunosensor was successfully applied for the detection of M. pneumoniae and L. pneumophila antigens in spiked water samples showing excellent recovery percentages. We attribute the high sensitivity of the immunosensor to the enhanced electrocatalytic characteristics, stability and conductivity of the GO–MOF composite as well as the synergistic interactions between the GO and MOF. This immunosensor offers a swift analytical response, simplicity in fabrication and instrumentation, rendering it an appealing platform for the on-field monitoring of pathogens in environmental samples.

Dual-modal biosensor for mercuric ion detection based on Cu2O@Cu2S/D-TA COF heterojunction with excellent catalase-like, electrochemical and photoelectrochemical properties

In this study, a dual-mode biosensor based on the heterojunction of Cu2O@Cu2S/D-TA COF was constructed for ultra-sensitive detection of Hg2+ using both photoelectrochemical and electrochemical approaches. Briefly, a 2D ultra-thin covalent organic framework film (D-TA COF film) with excellent photoelectrochemical signals was prepared on ITO surfaces through an in situ growth method. Subsequently, the probe H1 was immobilized onto the biosensor via Au–S bonds. In the presence of Hg2+, the formation of T-Hg2+-T complexes triggered hybridization chain reactions (HCR), leading to the attachment of abundant Cu2O@Cu2S probes onto the biosensor. As a p-type semiconductor, Cu2O@Cu2S could form a heterojunction with the underlying D-TA COF films. Meanwhile, it exhibited catalase-like activity, and the O2 produced by its catalytic decomposition of H2O2 can interact with the D-TA COF films, thus achieving double amplification of the photocurrent signal. Benefiting from the excellent and inherent Cu2+/Cu+ redox pairs of Cu2O@Cu2S, satisfactory differential pulse voltammetry (DPV) signals were obtained. As expected, the dual-mode biosensor was realized with wider linear ranges and low detection limits. Additionally, the analytical performance for Hg2+ in real water samples was excellent. Briefly, this suggested approach offers a facile and highly efficient modality for monitoring heavy metal ions in aquatic environments.

An ultra-sensitive electrochemical biosensor for circulating tumor DNA utilizing dual enzyme-assisted target recycle and hybridization chain reaction amplification strategies

Circulating tumor DNA (ctDNA) has emerged as a pivotal biomarker for cancers, offering a non-invasive means of detection through liquid biopsies. However, the current methodologies for ctDNA detection often struggle with sensitivity, especially when confronted with ultra-low concentrations. To address this challenge, we have engineered a remarkably sensitive electrochemical biosensor that can detect low concentration of ctDNA. This breakthrough is achieved by integrating a dual enzyme-assisted amplification mechanism with hybridization chain reaction (HCR). In the initial phase, the presence of ctDNA triggers the unfolding of the H2 hairpin structure, resulting in a segment of double-stranded DNA. The subsequent introduction of Klenow (3′→5′ exo-) and nicking endonuclease (Nb.BbvCI) enzymes leads to the abundant production of extended DNA (EXTDNA). This step critically enhances the initial amplification of the target DNA, ensuring superior specificity and selectivity thanks to the synergistic enzymatic activity. EXTDNA efficiently unfolds the H1 hairpin structure immobilized on the gold electrode, which acts as the initiation point for the HCR. Further amplification of the trace target DNA is achieved through an additional H3 and H4 hybrid-mediated HCR. Finally, the differential pulse voltammetry signal of methylene blue is increased significantly. Our results reveal that the developed electrochemical biosensor displays an exceptional linear correlation with ctDNA across concentrations ranging from 10 fM to 20 pM, with an unprecedented detection limit of 2.3 fM (3 s/k). This innovative approach shows immense potential for the ultrasensitive detection of ctDNA, promising broad applications in early cancer detection and monitoring.

A novel electropolymerized molecularly imprinted dual-mode sensor for bisphenol AF detection in pond mud

Recently, bisphenol AF (BPAF) as most commonly used bisphenol A analogs had the increasing higher level in the environment with unknown risks. Herein, a synchronous dual-mode sensor had been established based on differential pulse voltammetry (DPV) and electrochemiluminescence (ECL) for the detection of BPAF in pond mud. Firstly, the sensing molecularly imprinted polymer (MIP) films were prepared by electrochemical polymerization procedure with 3,4-ethoxylene dioxy thiophene (EDOT) as the functional monomer, BPAF as the template molecule and MXene as the supporting electrolyte. Due to unique characters of PEDOT and MXene, the constructed MIP films were stable and highly conductive. Meanwhile, zinc-doped bismuth sulfide quantum dots (Zn-Bi2S3 QDs) were synthesized as a nano-emitter to generate strong ECL signals in the MIP film. In the sensing process, a pulsed voltage applied to the PEDOT/MXene MIP film to generate both DPV and ECL signals for simultaneous dual-mode detection. Additionally, the liquid-liquid extraction with deep eutectic solvent (menthol: octanol 1:1) was used for the pre-concentration of the BPAF in the pond mud. Based on the sensing system, the ECL and DPV response showed the good linear relationships with the concentration of BPAF with the ranges of 0.01 μM–50 μM and 0.1 μM–50 μM and the detection limits of 0.0060 μM and 0.059 μM, respectively.

Development of a dual-mode Ru-UiO-TPEA MOF probe for highly sensitive and accurate detection of Cu2+ in biological systems

Cu2+ serves as a significant biomarker in various physiological processes. This study presents the development of a novel Ru-UiO-TPEA functionalized metal-organic framework (MOFs) probe for Cu2+ detection, employing both electrochemiluminescence (ECL) and electrochemical (EC) methods. Employing a dual ligand-assisted energy transfer approach, we synthesized Ru-UiO with optimal ECL and EC properties by adjusting the synthesis ratio of biphenyldicarboxylic acid to Ru(dcbpy)32+. This was followed by its conjugation with N-(2-aminoethyl)-N, N′, N′-tris(pyridin-2-ylmethyl) ethane-1,2-diamine (AE-TPEA) to form the highly conjugated Ru-UiO-TPEA probe for Cu2+ detection. As the Cu2+ concentration increased, the probe exhibited a diminished ECL signal and an enhanced differential pulse voltammetry (DPV) signal. The dual-mode detection method enabled cross-validation of the ECL and EC signals, enhancing accuracy and effectively minimizing errors. The ECL and EC methods had detection limits of 0.26 nM (range: 1 nM to 10 μM) and 0.65 nM (range: 2 nM to 80 μM), respectively. Meanwhile, these two methods can effectively detect Cu2+ in rat brain microdialysis fluid. Notably, the measured concentrations correlated well with those determined by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), highlighting its potential in biological and clinical bioelectronic sensing applications.

A fluorescence-electrochemical dual-mode aptasensor based on novel DNA-dependent PBNFs@PtPd for highly selective and sensitive detection of procymidone through hybridization chain reaction

Herein, a study for the first application of a hybridization chain reaction, a 1,8-naphthalimides-DNA (NDs) intercalator, and DNA-dependent Prussian blue nanoflowers@PtPd materials (PBNFs@PtPd) in the development of a fluorescence-electrochemical (FL-EC) aptasensor. This construction establishes an efficient sensing platform for the detection of procymidone (PCM). In the context of the described experiment, dual-mode detection is achieved through the generation of FL signals by an aptamer labeled with a Cy5 moiety and the formation of DPV signals by the modification of a thionine-appended 1,8-naphthalimide (Thi-NDs). In the presence of PCM, specific recognition occurs, followed by the utilization of magnetic separation technology to release DNA1 (S1) and aptamer-Cy5 (Apt-Cy5), subsequently introducing them onto both fluorescence and EC platforms. The presence of S1 effectively activates hybridization chain reaction (HCR) for the electrode surface, thereby significantly increasing the binding sites for Thi-NDs and consequently greatly amplifying the response signal of differential pulse voltammetry (DPV). The developed FL-EC dual-mode sensing platform demonstrates high sensitivity in the detection of PCM, with the detection limits of 0.173 μg·ml−1 (within the detection range of 500 pg·ml−1 to 500 ng·ml−1) and 0.074 ng·ml−1 (within the detection range of 100 pg·ml−1 to 100 ng·ml−1), respectively. The designed dual-mode sensor exhibits notable characteristics, including high selectivity, reproducibility, synergy, and reliable monitoring/capability for PCM in real samples.

A dual-signal output electrochemical aptasensor for glypican-3 ultrasensitive detection based on reduced graphene oxide-cuprous oxide nanozyme catalytic amplification strategy

Glypican-3 (GPC3) is an essential reference target for hepatocellular carcinoma detection, follow-up and prediction. Herein, a dual-signal electrochemical aptasensor based on reduced graphene oxide-cuprous oxide (RGO-Cu2O) nanozyme was developed for GPC3 detection. The RGO-Cu2O nanoenzyme displayed excellent electron transport effect, large specific surface area and outstanding peroxidase-like ability. The differential pulse voltammetry (DPV) signal of Cu2O oxidation fraction and the chronoamperometry (i-t) signal of H2O2 decomposition catalyzed by RGO-Cu2O nanozyme were used as dual-signal detection. Under optimal conditions, the log-linear response ranges were 0.1 to 500.0 ng/mL with the limit of detection 0.064 ng/mL for DPV technique, and 0.1–50.0 ng/mL for i-t technique (detection limit of 0.0177 ng/mL). The electrochemical aptasensor has remarkably analytical performance with wide response range, low detection limit, excellent repeatability and specificity, good recovery in human serum samples. The two output signals of one sample achieve self-calibration of the results, effectively avoiding the occurrence of possible leakage and misdiagnosis of a single detection signal, suggesting that it will be a promising method in the early biomarker detection.

Electrochemical genosensor based on RNA-responsive human telomeric G-quadruplex DNA: A proof-of-concept with SARS-CoV-2 RNA

In this report, a facile and label-free electrochemical RNA biosensor is developed by exploiting methylene blue (MB) as an electroactive positive ligand of G-quadruplex. The electrochemical response mechanism of the nucleic acid assay was based on the change in differential pulse voltammetry (DPV) signal of adsorbed MB on the immobilized human telomeric G-quadruplex DNA with a loop that is complementary to the target RNA. Hybridization between synthetic positive control RNA and G-quadruplex DNA probe on the transducer platform rendered a conformational change of G-quadruplex to double-stranded DNA (dsDNA), and increased the redox current of cationic MB π planar ligand at the sensing interface, thereby the electrochemical signal of the MB-adsorbed duplex is proportional to the concentration of target RNA, with SARS-CoV-2 (COVID-19) RNA as the model. Under optimal conditions, the target RNA can be detected in a linear range from 1 zM to 1 μM with a limit of detection (LOD) obtained at 0.59 zM for synthetic target RNA and as low as 1.4 copy number for positive control plasmid. This genosensor exhibited high selectivity towards SARS-CoV-2 RNA over other RNA nucleotides, such as SARS-CoV and MERS-CoV. The electrochemical RNA biosensor showed DPV signal, which was proportional to the 2019-nCoV_N_positive control plasmid from 2 to 200000 copies (R2 = 0.978). A good correlation between the genosensor and qRT-PCR gold standard was attained for the detection of SARS-CoV-2 RNA in terms of viral copy number in clinical samples from upper respiratory specimens.

Toward Remote Detection of Chemical Warfare Simulants Using a Miniature Potentiostat

A miniaturized electrochemical sensor was developed for the remote detection of chemical warfare agent (CWA) simulants. To facilitate drone-based remote sensing, this present study focuses on advancing the miniaturized and compact electrochemical sensor for monitoring two CWA simulants, diisopropyl fluorophosphate (DFP) and O,S-diethylmethylphosphonothioate (O,S-DEMPT). The differential pulse voltammetry (DPV) signal was processed, and the DPV signature features were extracted on the basis of the redox properties associated with the absence and the presence of DFP and O,S-DEMPT. Upon the addition of 0.10 equivalence of DFP or O,S-DEMPT, a shift in potential (E) of ~0.13 V was recorded. The limit of detection (LOD) was calculated to be 0.25 µM (0.046 ppm) and 0.10 µM (0.017 ppm) for DFP and O,S-DEMPT, respectively. These results were validated using a portable Palmsens Emstat HR potentiostat, which corroborated the results obtained using a lab benchtop potentiostat. Additionally, Boolean logic (“AND” operation) was implemented for future drone technology deployment. This advancement enables the fabrication of a networked device capable of autonomously executing tasks without constant oversight.

Highly sensitive electrochemical biosensor for MUC1 detection based on DNA-functionalized CdTe quantum dots as signal enhancers.

In this paper, an electrochemical biosensor based on a cadmium telluride/polypyrrole (CdTe/PPy) nanocomposite was developed for the detection of MUC1 with high selectivity and sensitivity. Results indicate that the CdTe/PPy nanocomposite is modified on the surface of the glassy carbon electrode (GCE), which affords a large surface area for immobilizing cap-DNA, ensuring its high selectivity and sensitivity. Next, CdTe-linked sig-DNA (MUC1 aptamer) was introduced, allowing the MUC1 aptamer to hybridize with cap-DNA. CdTe is a signal amplification element used to generate a differential pulse voltammetry (DPV) signal. Conceivably, target MUC1 detection was based on current signal change due to concentration change in the signal amplification element CdTe. In the presence of MUC1, the MUC1 aptamer specifically binds to MUC1, resulting in the release of CdTe-sig-DNA from the electrode surface and a decrease in peak current. Under optimized experimental conditions, the electrochemical biosensor is highly selective, sensitive, stable, and reproducible for MUC1 ranging from 0.1 nM to 100 nM with a detection limit of 0.05 nM (S/N = 3). Therefore, the electrochemical biosensor has potential applications in medical disease diagnosis.

Sensitive electrochemical detection of l-tryptophan using a glassy carbon electrode modified with pectin extracted from Arthrocnemum indicum leaves

Pectin from Arthrocnemum indicum leaves (PAI) extracted from plants, harvested in the Tunisian Sahel, was used for the first time as a sensitive matrix for the design of an electrochemical sensor of l-tryptophan via differential pulse voltammetry (DPV). A glassy carbon electrode (GCE) was modified by a PAI layer through simple adsorption, leading to a DPV signal of l-tryptophan that was increased by a factor of 15. The PAI-modified electrode exhibited a good analytical performance towards the detection of l-tryptophan with a wide linear range between 9.10−5 mM to 2.10−2 mM, a detection limit of 0.09 µM, and a sensitivity of 90.15 µA. mM−1. Compared to other reported electrochemical sensors, PAI/GCE presents a lower detection limit, even without the use of nanomaterials. In addition, the PAI/GCE showed good reproducibility and good selectivity towards the determination of l-tryptophan versus other amino acids, uric acid, and ascorbic acid, making it suitable for the determination of l-tryptophan in biological fluids.

An electrochemical biosensor based on phage-encoded protein RBP 41 for rapid and sensitive detection of Salmonella

Salmonellosis caused by Salmonella contaminated food poses a serious threat to human health. The rapid and accurate detection of Salmonella is critical for preventing foodborne illness outbreaks. In this study, an electrochemical biosensor was developed using a newly identified biorecognition element, RBP 41, which is capable of specifically recognizing and binding to Salmonella. The biosensor was constructed through a layer-by-layer assembly of graphene oxide (GO), gold nanoparticles (GNPs), and RBP 41 on a glassy carbon electrode (GCE), with the GNPs amplifying the detection signal. The established biosensor was able to detect Salmonella in concentrations ranging from 3 to 106 CFU/mL within approximately 30 min by using differential pulse voltammetry (DPV) signal, and the estimated detection limit was to be 0.2984 Log10 CFU/mL. The biosensor demonstrated excellent specificity and was effective in detecting Salmonella in food matrices, such as skim milk and lettuce. Overall, this study highlights the potential of phage tail receptor binding proteins in biosensing and the proposed biosensor as a promising alternative for rapid and sensitive Salmonella detection in various samples.

A target-triggered ultra-sensitive aptasensor for simultaneous detection of Cd2+ and Hg2+ using MWCNTs-Au NPs modified electrode

A sensitive electrochemical assay for simultaneously detecting cadmium ion (Cd2+) and mercury ion (Hg2+) with the aptamer as recognition unit was established, in which methylene blue (MB) and target-triggered in-situ generated Ag nanoclusters (Ag NCs) were identified as signal reporters. Multi-walled carbon nanotubes and gold nanoparticles composites were prepared with polyethyleneimine to amplify electrical signals of screen-printed electrodes. Due to the particular base sequences, MB labeled Cd2+ aptamer paired with ssDNA through T-Hg-T structure with Hg2+. Notably, the C-rich structure in ssDNA acted as a template for the generation of Ag NCs, which could induce differential pulse voltammetry signals corresponding to Hg2+ concentrations. This electrochemical aptasensor exhibited detection limits of 94.01 pg/mL and 15.74 pg/mL for Cd2+ and Hg2+, respectively. The developed aptasensor allowed for practical application to tea and vegetable samples with satisfactory accuracy. This work possesses potential in developing biosensing technologies for simultaneous determination of multiple heavy metals.

Construction of electrochemical biosensor based on magnetic Fe3O4/α-Fe2O3 heterogeneous nanorods for the sensitive detection of MUC1 mucoprotein

Magnetic Fe3O4/α-Fe2O3 heterogeneous nanorods with the saturation magnetization of 69.5 emu/g were prepared via the hydrothermal and calcination-reduction process using β-FeOOH nanorods as precursor and galactose as the reducing agent. The average length and diameter of the nanorods were 81.6 nm and 23.9 nm, respectively. The surfaces of the heterogeneous nanorods were modified with PEI and HAuCl4, resulting in magnetic rod-like Fe3O4/α-Fe2O3@Au nanocomposites. By utilizing the Au–S effect, Apt/ssDNA hybrid double-strands were loaded onto Fe3O4/α-Fe2O3@Au nanocomposites to form Fe3O4/α-Fe2O3@Au-Apt/ssDNA biosensors capable of recognizing mucoprotein-1 (MUC1) mucoprotein. These biosensors could be magnetically assembled onto a magnetic glassy carbon electrode to create a "Turn off" type electrochemical biosensor. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV) techniques were used to evaluate the detection performance. Based on the change in DPV signals, the optimal concentrations of magnetic Fe3O4/α-Fe2O3@Au nanocomposites and Apt/ssDNA double-stranded probes were 12 mg/mL and 9 μM, respectively, while the optimal incubation time was 2 h. Under these conditions, the sensor exhibited a linear detection range of 0.1 pg/mL to 1500 pg/mL (R2 = 0.9988), with a limit of detection (LOD) of 0.1 pM and a limit of quantitation (LOQ) of 0.34 pM. The biosensor demonstrated excellent performance in terms of selectivity, reproducibility (RSD = 2.9 %), and stability. When actual serum samples diluted by a factor of 20 in PBS were tested, the recovery rate ranged from 95.65 % to 103.40 %, indicating that this approach for sensitive detection of MUC1 holds promising prospects.

Highly sensitive electrochemical peptide-based biosensor for marine biotoxin detection using a bimetallic platinum and ruthenium nanoparticle-tethered metal-organic framework modified electrode.

Saxitoxin (STX) is a highly toxic small-molecule cyanotoxin that is water-soluble, stable in acidic media, and thermostable. STX is hazardous to human health and the environment in ocean, thus it is an important to detect it at very low concentrations. Herein, we developed an electrochemical peptide-based biosensor for the trace detection of STX in different sample matrix utilizing differential pulse voltammetry (DPV) signal. We synthesized the nanocomposite of zeolitic imidazolate framework-67 (ZIF-67) decorated bimetallic platinum (Pt) and ruthenium (Ru) nanoparticles (Pt-Ru@C/ZIF-67) using impregnation method. The nanocomposite modified with screen-printed electrode (SPE) was subsequently used to detect STX in the range of 1-1,000ngmL-1, with a detection limit (LOD) of 26.7pgmL-1. The developed peptide-based biosensor is highly selective and sensitive towards STX detection, thus it represents a promising strategy for the development of novel portable bioassay for monitoring various hazardous molecules in aquatic food chains.

Tetrahedral DNA Nanostructure-Engineered Paper-Based Electrochemical Aptasensor for Fumonisin B1 Detection Coupled with Au@Pt Nanocrystals as an Amplification Label.

Fumonisin B1 (FB1), as one of the highest toxicity mycotoxins, poses a serious threat to animal and human health, even at low concentrations. It is significant and challenging to develop a sensitive and reliable analytical device. Herein, a paper-based electrochemical aptasensor was designed utilizing tetrahedral DNA nanostructures (TDNs) to controllably anchor an aptamer (Apt), improving the recognition efficiency of Apt to its target. First, gold nanoparticles (AuNPs)@MXenes were used as a sensing substrate with good conductivity and modified on the electrode for immobilization of complementary DNA-TDNs (cDNA-TDNs). In the absence of FB1, numerous Apt-Au@Pt nanocrystals (NCs) was hybridized with cDNA and assembled on the sensing interface, which accelerated the oxidation of TMB with H2O2 and produced a highly amplified differential pulse voltammetry (DPV) signal. When the target FB1 specifically bound to its Apt, the electrochemical signal was decreased by releasing the Apt-Au@Pt NCs from double-stranded DNA (dsDNA). On account of the strand displacement reaction by FB1 triggering, the aptasensor had a wider dynamic linear range (from 50 fg/mL to 100 ng/mL) with a lower limit of detection (21 fg/mL) under the optimized conditions. More impressively, the designed FB1 aptasensor exhibited satisfactory performance in corn and wheat samples. Therefore, the TDN-engineered sensing platform opens an effective approach for sensitive and accurate analysis of FB1, holding strong potential in food safety and public health.

Dual-mode transfer response based on electrochemical and fluorescence signals for the detection of amyloid-beta oligomers (AβO).

An aptamer sensor has been developedutilizing a dual-mode and stimuli-responsive strategy for quantitative detection of AβO (amyloid-beta oligomers) through simultaneous electrochemical and fluorescence detection. To achieve this, we employed UIO-66-NH2 as a carrier container to load MB (Methylene Blue), and Fe3O4 MNPs (iron oxide magnetic nanoparticles) with aptamer (ssDNA-Fe3O4 MNPs) fixed on their surface for biological gating. The ssDNA-Fe3O4 MNPs were immobilized onto the surface of UIO-66-NH2 through hydrogen bonding between the aptamer and the -NH2 group on the surface of UIO-66-NH2, thereby encapsulating MB and forming ssDNA-Fe3O4@MB@UIO-66-NH2. During the detection of AβO, the aptamer selectively reacted with AβO to form the AβO-ssDNA-Fe3O4 complex, leading to its detachment from the surface of UIO-66-NH2. This detachment facilitated the release of MB, enabling its electrochemical detection. Simultaneously, the AβO-ssDNA-Fe3O4 complex was efficiently collected and separated using a magnet after leaving the container's surface. Furthermore, the addition of NaOH facilitated the disconnection of biotin modifications at the 3' end of the aptamer from the avidin modifications on the Fe3O4 MNPs. Consequently, the aptamer detached from the surface of Fe3O4 MNPs, resulting in the restoration of fluorescence intensity of FAM (fluorescein-5'-carboxamidite) modified at its 5' end for fluorescence detection. The dual-mode sensor exhibited significantly enhanced differential pulse voltammetry signals and fluorescence intensity compared to those in the absence of AβO. The sensor demonstrated a wide detection range of 10 fM to 10 μM, with a detection limit of 3.4 fM. It displayed excellent performance in detecting actual samples and holds promising prospects for early diagnosis of Alzheimer's disease.