Ultrasensitive 3D Stacked Silicon Nanosheet Field-Effect Transistor Biosensor with Overcoming Debye Shielding Effect for Detection of DNA.

Silicon nanowire field effect (SiNW-FET) biosensors have been successfully used in the detection of nucleic acids, proteins and other molecules owing to their advantages of ultra-high sensitivity, high specificity, and label-free and immediate response. However, the presence of the Debye shielding effect in semiconductor devices severely reduces their detection sensitivity. In this paper, a three-dimensional stacked silicon nanosheet FET (3D-SiNS-FET) biosensor was studied for the high-sensitivity detection of nucleic acids. Based on the mainstream Gate-All-Around (GAA) fenestration process, a three-dimensional stacked structure with an 8 nm cavity spacing was designed and prepared, allowing modification of probe molecules within the stacked cavities. Furthermore, the advantage of the three-dimensional space can realize the upper and lower complementary detection, which can overcome the Debye shielding effect and realize high-sensitivity Point of Care Testing (POCT) at high ionic strength. The experimental results show that the minimum detection limit for 12-base DNA (4 nM) at 1 × PBS is less than 10 zM, and at a high concentration of 1 µM DNA, the sensitivity of the 3D-SiNS-FET is approximately 10 times higher than that of the planar devices. This indicates that our device provides distinct advantages for detection, showing promise for future biosensor applications in clinical settings.

Click Reaction-Mediated Fluorescent Immunosensor Based on Cu-MOF Nanoparticles for Ultrasensitive and High-Throughput Detection of Aflatoxin B1 in Food Samples.

Due to the high toxicity of aflatoxin B1 and its risks to human health, we developed a click reaction-mediated automated fluorescent immunosensor (CAFI) for sensitive detection of aflatoxin B1 based on the Cu(I)-catalyzed click reaction. With its large specific surface area, a copper-based metal-organic framework (Cu-MOF) was synthesized to adsorb and enrich the copper ion (Cu(II)) and then load the complete antigen (BSA-AFB1). After the immunoreaction, Cu(II) inside the Cu-MOF-Antigen conjugate would be reduced to Cu(I) in the presence of sodium ascorbate, which triggered the click reaction between the fluorescent donor-modified DNA and the receptor-modified complementary DNA to lead to a fluorescence signal readout. The whole reaction steps were finished by the self-developed automated immunoreaction device. This CAFI method showed a limit of detection (LOD) of 0.48 pg/mL as well as a 670-fold enhancement in sensitivity compared to conventional ELISA, revealing its great potential in practical applications and automated detection.

One-pot, one-step, label-free miRNA detection method based on the structural transition of dumbbell probe.

In this study, we present a one-pot, one-step, label-free miRNA detection method through a structural transition of a specially designed dumbbell-shape probe, initiating a rolling circle transition (RCT). In principle, target miRNA binds to right loop of the dumbbell probe (DP), which allows structural change of the DP to circular form, exposing a sequence complementary to the T7 promoter (T7p) previously hidden within the stem. This exposure allows T7 RNA polymerase to initiate RCT, producing a repetitive Mango aptamer sequence. TO1-biotin, fluorescent dye, binds to the aptamer, inducing a detectable enhancement of fluorescence intensity. Without miR-141, the DP stays closed, RCT is prevented, and the fluorescence intensity remains low. By employing this novel strategy, target miRNA was successfully identified with a detection of 73 pM and a dynamic linear range of 0-10 nM. Additionally, the method developed enables one-pot, one-step, and label-free detection of miRNA, demonstrating potential for point-of-care testing (POCT) applications. Furthermore, the practical application of the designed technique was demonstrated by reliably detecting the target miRNA in the human serum sample. We also believe that the conceived approach could be widely used to detect not only miRNAs but also diverse biomolecules by simply replacing the detection probe.

Determination of the total antioxidant capacity of the Chinese tea based on a novel "peroxidase/zirconium phosphonate"composite electrochemical sensor.

In this work, a novel zirconium phosphonate (ZrPR1R2) was prepared by decorating both the aminoethoxy- group (R1) and the carboxypropyl- group (R2) on the zirconium phosphate layers in order to manipulate further the immobilization of the peroxidase (POD), and an antioxidant biosensor with higher sensitivity was constructed by dropping the POD/ZrPR1R2 composite onto the glassy carbon electrode surface. The activity of the POD/ZrPR1R2 composite was detected by Uv-vis spectra. The direct electrochemical behavior, the electrocatalytic response to dissolved oxygen and hydrogen peroxide, as well as the ability to detect total antioxidant capacity in tea sample were investigated by the methods of cyclic voltammetry. The results indicated that the immobilization of POD in ZrPR1R2 nanosheets matrix enhanced the enzymatic activity, and achieved the fast and direct electron transfer between POD and glassy carbon electrode. Moreover, the POD/ZrPR1R2 composite modified electrode show the electrocatalytic response to hydrogen peroxide in the linear range of 8.8×10-8 to 8.8×10-7 mol L-1, with the detection limit of 3.3×10-8 mol L-1. Attributing to the sensitive response to dissolved oxygen, the total antioxidant capacity can be detected directly in the real tea water by this POD/ZrPR1R2 composite modified electrode.

Target-Responsive DNA Nanoclaw for the On-Site Identification of Chinese Medicines with Naked Eye.

The identification of Chinese medicinal herbs occupies a crucial part in the development of the food and drug market. Although molecular identification based on real-time PCR offers good versatility and uniform digital standards compared with traditional methods, such as morphology, the dependence on large-scale equipment hinders spot detection and marketable applications. In this study, we developed a DNA nanoclaw for colorimetric detection and visible on-site identification of Chinese medicines. When specific miRNA is present, the DNAzyme is activated and cleaves the substrate strand, triggering the catalytic hairpin assembly (CHA) reaction and forming branched DNA junctions on AuNP-I. This can then capture AuNP-II through hybridization and facilitate their aggregation, resulting in a noticeable color change that is observable to the naked eye. By harnessing the dual amplification of DNAzyme and CHA, this highly sensitive nanoprobe successfully achieved specific identification of Chinese medicines. This offers a new perspective for on-site testing in the herbal market.

Sea hedgehog-inspired surface-enhanced Raman scattering biosensor probe for ultrasensitive determination of Staphylococcus aureus in food supplements.

Staphylococcus aureus contamination in food supplements poses substantial challenges to public health and large-scale production but the sensitive detection in a timely manner remains a bottleneck. Drawing inspiration from the sea hedgehog, gold nanostars (AuNSs) were leveraged to design an ultrasensitive surface-enhanced Raman scattering (SERS) biosensor for the determination of Staphylococcus aureus in food supplements. Besides the surface enhancement furnished by the AuNSs, Raman reporter molecules and specific aptamers sequentially self-assembled onto these AuNSs to construct the "three-in-one" SERS biosensor probe for label-based quantitation of Staphylococcus aureus. Following incubation with contaminated health product samples, the gold nanostars@Raman reporter-aptamer specifically recognize and assemble around Staphylococcus aureus cells, forming a distinctive sea hedgehog structure. This unique configuration results in an amplified Raman signal at 1338 cm-1 and an enhancement factor of up to 6.71 × 107. The entire quantitative detection process can be completed within 30 min, boasting an exceptional limit of detection as low as 1.0 CFU mL-1. The method exhibits a broad working range for the determination of Staphylococcus aureus, with concentrations spanning 2.15 CFU mL-1 to 2.15 × 105 CFU mL-1. Furthermore, it demonstrates outstanding precision, with relative standard deviation values consistently below 5.0%. As a showcase to validate the practicality of the SERS method, we conducted tests on determining Staphylococcus aureus in a herbal food supplement, i.e., Ginkgo Biloba extract (GBE); the results align closely with those obtained through the conventional lysogeny broth agar plate method, pointing to the potential applicability in real-world scenarios.

DNA-induced assembly of biocatalytic nanocompartments for sensitive and selective aptasensing of aflatoxin B1.

Enzyme cascade with high specificity and catalytic efficiency has significant applications for developing efficient bioanalysis methods. In this work, a sensitive and selective aptasensor was constructed based on the DNA-induced assembly of biocatalytic nanocompartments. Different from the conventional co-immobilization in one pot, the cascade enzymes of glucose oxidase (GOX) and horseradish peroxidase (HRP) were separately encapsulated in ZIF-90 nanoparticles. After conjugating complementary DNA or aptermer on enzyme@ZIF-90, DNA hybridization drove enzyme@ZIF-90 connected into clusters or linked on other DNA modified biocatalytic nanocompartment (such as invertase loaded Fe3O4@SiO2). Owing to the shortened distance between enzymes, the catalytic efficiency of connected clusters was significantly enhanced. However, the specifically interaction between the substrate molecule and aptermer sequence would lead to the disassembly of DNA duplexes, resulting in the gradual "switching-off" of cascade reactions. With aflatoxin B1 (AFB1) as the model substrate, the compartmentalized three-enzyme nanoreactors showed good analytical performance in the linear range from 0.01 ng mL-1 to 50 ng mL-1 with a low detection limit (3.3 pg mL-1). In addition, the proposed aptasensor was applied to detect AFB1 in corn oil and wheat powder samples with total recoveries ranging from 94 % to 109 %. As a result, this DNA-induced strategy for enzyme cascade nanoreactors opens new avenues for stimuli-responsive applications in biosensing.

A photoelectrochemical aptasensor for omethoate determination based on a photocatalysis of CeO2@MnO2 heterojunction for glucose oxidation.

In the present work, we developed a photoelectrochemical aptasensor to determine omethoate (OMT) based on the dual signal amplification of CeO2@MnO2 photocatalysis for glucose oxidation and exonuclease I-assisted cyclic catalytic hydrolysis. CeO2@MnO2 heterojunction material prepared by hydrothermal method was linked with captured DNA (cDNA) and then assembled on the ITO conductive glass to form ITO/CeO2@MnO2-cDNA, which exhibited significant photocurrent response and good photocatalytic performance for glucose oxidation under visible light irradiation, providing the feasibility for sensitive determining OMT. After binding with the aptamer of OMT (apt), the formation of rigid double stranded cDNA/apt kept CeO2@MnO2 away from ITO surface, which ensured a low photocurrent background for the constructed ITO/CeO2@MnO2-cDNA/apt aptasensor. In the presence of target OMT, the restoration of the cDNA hairpin structure and the exonuclease I-assisted cyclic catalytic hydrolysis led to the generation and amplification of measurement photocurrent signals, and allowed the aptasensor to have an ideal quantitative range of 0.01-10.0 nM and low detection limit of 0.0027 nM. Moreover, the aptasensor has been applied for selective determination of OMT in real samples with good precision of the relative standard deviation less than 6.2 % and good accuracy of the recoveries from 93 % to 108 %. What's more, the aptasensor can be used for other target determination only by replacing the captured DNA and corresponding aptamer.

Label-free and highly-sensitive detection of calcium ions using a silicon-on-sapphire light-addressable potentiometric sensor.

BACKGROUND: Ionic calcium (Ca2+) plays a crucial role in maintaining normal physiological and biochemical functions within the human body. Detecting the concentration of Ca2+ is of utmost significance for various purposes, including disease screening, cellular metabolism research, and evaluating drug effectiveness. However, current detection approaches such as fluorescence and colorimetry face limitations due to complex labeling techniques and the inability to track changes in Ca2+ concentration. In recent years, extensive research has been conducted in this field to explore label-free and efficient approaches. RESULTS: In this study, a novel light-addressed potentiometric sensor (LAPS) using silicon-on-sapphire technology, has been successfully developed for Ca2+ sensing. The Ca2+-sensitive LAPS achieved a wide-range detection of Ca2+, ranging from 10-2 M to 10-7 M, with an impressive detection limit of 100 nM. These advancements are attributed to the ultra-thin silicon layer, silicon dioxide layer, and solid-state silicon rubber sensitive membrane around 6 µm. Furthermore, the sensor demonstrated the ability to dynamically monitor fluctuations in Ca2+ concentration ranging from 10-9 M to 10-2 M within a solution. Its remarkable selectivity, specificity, and long-term stability have facilitated its successful application in the detection of Ca2+ in human serum and urine. SIGNIFICANCE AND NOVELTY: This work presents a Ca2+-sensitive sensor that combines a low detection limit and a wide detection range. The development represents the emergence of a label-free and rapid Ca2+ detection tool with immense prospects in home-based health monitoring, community disease screening, as well as cellular metabolism, and drug screening evaluations.

Ultrasensitive electrochemiluminescence biosensor based on dual quenching effects of silver nanoclusters and multiple cycling amplification for detection of ATP.

In this work, an electrochemiluminescence (ECL) biosensor based on dual ECL quenching effects of silver nanoclusters (Ag NCs) and multiple cycling amplification was designed to achieve ultrasensitive detection of ATP. The specific recognition of target ATP to aptamer initiated multiple cycling amplification, and a small amount of target was converted into a large number of DNA product chains (S1) by amplification. After S1 opened hairpin DNA 2 (HP2), Ag NCs approached the surface of CdS quantum dots (QDs) modified-electrode by complementary DNA, resulting in a significant decrease of ECL intensity from CdS QDs. The quenching principle is as follows. Firstly, the absorption spectrum of Ag NCs overlaps well with the ECL emission spectrum of CdS QDs, leading to effective ECL resonance energy transfer (ECL-RET); Secondly, Ag NCs could catalyze electrochemical reduction of K2S2O8, leading to consumption of ECL co-reactant and reducing ECL of QDs. The double-ECL quenching achieved ultrasensitive biosensing detection of ATP with a wide range from 1 aM to 1 pM. This present work reported new principle of double-quenching QDs ECL by Ag NCs, and developed a novel ECL biosensor by combining with multiple cycle amplification technique, which has great contribution to the development of QDs ECL and biosensing applications.

Nucleic acid aptamer based thermally oxidized porous silicon/zinc oxide microarray chip for detection of ochratoxin A in cereals.

A nucleic acid aptamer based thermally oxidized porous silicon/zinc oxide microarray chip was constructed for the detection of ochratoxin A. The hybrid chains formed by aptamer and complementary chains labeled with fluorescent groups and fluorescent burst groups were used as recognition molecules, and the detection of toxins was accomplished on the chip by the principle of fluorescence signal burst and recovery. The modified QuEChERS method was used for sample pretreatment and the performance of the method was evaluated. The results showed that the linear range was 0.02 âˆ¼ 200 ng/kg with the detection limit of 0.0196 ng/kg under the optimal detection conditions. The method was applied to different cereals with the recoveries of 90.30 âˆ¼ 111.69 %. The developed microarray chip has the advantages of being cost-effective, easy to prepare, sensitive and specific, and can provide a new method for the detection of other toxins.

Pseudouridine-modified RNA probe for label-free electrochemical detection of nucleic acids on 2D MoS2 nanosheets.

RNA modification, particularly pseudouridine (Ψ), has played an important role in the development of the mRNA-based COVID-19 vaccine. This is because Ψ enhances RNA stability against nuclease activity and decreases the anti-RNA immune response. Ψ also provides structural flexibility to RNA by enhancing base stacking compared with canonical nucleobases. In this report, we demonstrate the first application of pseudouridine-modified RNA as a probe (Ψ-RNA) for label-free nucleic acid biosensing. It is known that MoS2 has a differential affinity for nucleic acids, which may be translated into a unique electronic signal. Herein, the Ψ-RNA probe interacts with the pristine MoS2 surface and causes a change in interfacial electrochemical charge transfer in the MoS2 nanosheets. Compared with an unmodified RNA probe, Ψ-RNA exhibited faster adsorption and higher affinity for MoS2. Moreover, Ψ-RNA could bind to complementary RNA and DNA targets with almost equal affinity when engaged with the MoS2 surface. Ψ-RNA maintained robust interactions with the MoS2 surface following the hybridization event, perhaps through its extra amino group. The detection sensitivity of the Ψ-RNA/MoS2 platform was as low as 500 attomoles, while the results also indicate that the probe can distinguish between complementary targets, single mismatches, and non-complementary nucleic acid sequences with statistical significance. This proof-of-concept study shows that the Ψ-RNA probe may solve numerous problems of adsorption-based biosensing platforms due to its stability and structural flexibility.

Measurement of microRNA-106b as a gastric cancer biomarker based on Zn-BTC MOF label-free genosensor.

Due to the late detection of stomach cancer, this cancer usually causes high mortality. The development of an electrochemical genosensor to measure microRNA 106b (miR-106b), as a gastric cancer biomarker, is the aim of this effort. In this regard, first, 1,3,5-benzenetricarboxylate (BTC) metal-organic frameworks (Zn-BTC MOF) were self-assembled on the glassy carbon electrode and then the probe (ssDNA) was immobilized on it. The morphology Zn-BTC MOF was characterized by SEM, FT-IR, Raman and X-Ray techniques. Zn-BTC MOF as a biosensor substrate has strong interaction with ssDNA. Quantitative measurement of miR-106b was performed by electrochemical impedance spectroscopy (EIS). To perform this measurement, the difference of the charge transfer resistances (ΔRct) of Nyquist plots of the ssDNA probe modified electrode before and after hybridization with miR-106b was obtained and used as an analytical signal. Using the suggested genosensor, it is possible to measure miR-106b in the concentration range of 1.0 fM to 1.0 µM with a detection limit of 0.65 fM under optimal conditions. Moreover, at the genosensor surface, miR-106b can be detected from a non-complementary and a single base mismatch sequence. Also, the genosensor was used to assess miR-106b in a human serum sample and obtained satisfactory results.

Multidimensional Applications and Challenges of Riboswitches in Biosensing and Biotherapy.

Riboswitches have received significant attention over the last two decades for their multiple functionalities and great potential for applications in various fields. This article highlights and reviews the recent advances in biosensing and biotherapy. These fields involve a wide range of applications, such as food safety detection, environmental monitoring, metabolic engineering, live cell imaging, wearable biosensors, antibacterial drug targets, and gene therapy. The discovery, origin, and optimization of riboswitches are summarized to help readers better understand their multidimensional applications. Finally, this review discusses the multidimensional challenges and development of riboswitches in order to further expand their potential for novel applications.

Nanoplasmonic biosensors for multicolor visual analysis of acetylcholinesterase activity and drug inhibitor screening in point-of-care testing.

The monitoring of acetylcholinesterase (AChE) activity and the screening of its inhibitors are significance of the diagnosis and drug therapy of nervous diseases. A metal ions-mediated signal amplification strategy was developed for the highly sensitive and multicolor assay of AChE activity and visually screening its drug inhibitors. After the specific reaction between AChE and acetylthiocholine (ATCh), the hydrolysis product thiocholine (TCh) can directly and decompose the α-FeOOH nanorods (NRs) to release amounts of Fe2+, which was regarded as Fenton reagent to efficiently catalyze H2O2 to produce ·OH. Then, the as-formed ·OH can further largely shorten the gold nanobipyramids (Au NBPs), generating a series of palpable color variations. The linear range for AChE activity was 0.01-500.0 U/L with the limit of detection as low as 0.0074 U/L. The vivid visual effects could be easily distinguished for the multicolor assay of AChE activity by naked eye in visible light. To achieve the point-of-care testing, Au NBPs were further assembled on polymeric electrospun nanofibrous films (ENFs) surface as test strips for the easy-to-use test of AChE activity by RGB values with a smartphone. Fascinatingly, this proposed strategy can be used for the visual screening AChE inhibitors or non-inhibitors. Comparing with the clinical drugs (rivastigmine tartrate, and donepezil), some natural alkaloids such as evodiamine, caffeine, camptothecin, and berberine hydrochloride were selected as inhibitor modes to confirm the drug screening capability of this method. This proposed strategy may have great potential in the other disease-related enzymatic biomarkers assay and the rapid screening of drug therapy.

A "signal off-on" fluorescence bioassay based on 2D-MoS2-tetrahedral DNA bioconjugate for rapid virus detection.

In this work we present the preparation of a 2D molybdenum disulphide nanosheets (2D-MoS2) and tetrahedral DNA nanostructures (TDNs) bioconjugate, and its application to the development of a bioassay for rapid and easy virus detection. The bioconjugate has been prepared by using TDNs carrying the capture probe labelled with 6-carboxyfluoresceine (6-FAM). As case of study to assess the utility of the assay developed, we have chosen the SARS-CoV-2 virus. Hence, as probe we have used a DNA sequence complementary to a region of the SARS-CoV-2 ORF1ab gene (TDN-ORF-FAM). This 6-FAM labelled capture probe is located on the top vertex of the tetrahedral DNA nanostructure, the three left vertices of TDNs have a thiol group. These TDNs are bounded to 2D-MoS2 surface through the three thiol groups, allowing the capture probe to be oriented to favour the biorecognition reaction with the analyte. This biorecognition resulting platform has finally been challenged to the detection of the SARS-CoV-2 ORF1ab gene sequence as the target model by measuring fluorescence before and after the hybridization event with a detection limit of 19.7fM. Furthermore, due to high sensitivity of the proposed methodology, it has been applied to directly detect the virus in nasopharyngeal samples of infected patients without the need of any amplification step. The developed bioassay has a wide range of applicability since it can be applied to the detection of any pathogen by changing the probe corresponding to the target sequence. Thus, a novel, hands-on strategy for rapid pathogen detection has proposed and has a high potential application value in the early diagnosis of infections causes by virus or bacteria.

Low-Cost Plant-Based Metal and Metal Oxide Nanoparticle Synthesis and Their Use in Optical and Electrochemical (Bio)Sensors.

Technological progress has led to the development of analytical tools that promise a huge socio-economic impact on our daily lives and an improved quality of life for all. The use of plant extract synthesized nanoparticles in the development and fabrication of optical or electrochemical (bio)sensors presents major advantages. Besides their low-cost fabrication and scalability, these nanoparticles may have a dual role, serving as a transducer component and as a recognition element, the latter requiring their functionalization with specific components. Different approaches, such as surface modification techniques to facilitate precise biomolecule attachment, thereby augmenting recognition capabilities, or fine tuning functional groups on nanoparticle surfaces are preferred for ensuring stable biomolecule conjugation while preserving bioactivity. Size optimization, maximizing surface area, and tailored nanoparticle shapes increase the potential for robust interactions and enhance the transduction. This article specifically aims to illustrate the adaptability and effectiveness of these biosensing platforms in identifying precise biological targets along with their far-reaching implications across various domains, spanning healthcare diagnostics, environmental monitoring, and diverse bioanalytical fields. By exploring these applications, the article highlights the significance of prioritizing the use of natural resources for nanoparticle synthesis. This emphasis aligns with the worldwide goal of envisioning sustainable and customized biosensing solutions, emphasizing heightened sensitivity and selectivity.

Detection of Various Traditional Chinese Medicinal Metabolites as Angiotensin-Converting Enzyme Inhibitors: Molecular Docking, Activity Testing, and Surface Plasmon Resonance Approaches.

Angiotensin-converting enzyme 1 (ACE1) is a peptide involved in fluid and blood pressure management. It regulates blood pressure by converting angiotensin I to angiotensin II, which has vasoconstrictive effects. Previous studies have shown that certain compounds of natural origin can inhibit the activity of angiotensin-converting enzymes and exert blood pressure-regulating effects. Surface Plasmon Resonance (SPR) biosensor technology is the industry standard method for observing biomolecule interactions. In our study, we used molecular simulation methods to investigate the docking energies of various herbal metabolites with ACE1 proteins, tested the real-time binding affinities between various herbal metabolites and sACE1 by SPR, and analyzed the relationship between real-time binding affinity and docking energy. In addition, to further explore the connection between inhibitor activity and real-time binding affinity, several herbal metabolites' in vitro inhibitory activities were tested using an ACE1 activity test kit. The molecular docking simulation technique's results and the real-time affinity tested by the SPR technique were found to be negatively correlated, and the virtual docking technique still has some drawbacks as a tool for forecasting proteins' affinities to the metabolites of Chinese herbal metabolites. There may be a positive correlation between the enzyme inhibitory activity and the real-time affinity detected by the SPR technique, and the results from the SPR technique may provide convincing evidence to prove the interaction between herbal metabolites and ACE1 target proteins.

Biosensing with Polymerase Chain Reaction-Stable DNA-Functionalized Magnetically Susceptible Carbon-Iron Microparticles.

We demonstrate a rapid and sensitive method for DNA detection without the need for fluorescence. This is based on carbon-coated magnetic iron (Fe) microparticles with a covalent surface attachment of DNA. We show that these magnetic microparticles can capture complementary DNA. Significantly, the DNA covalent surface bonds are robust to high temperatures and can be included in a sample during polymerase chain reaction (PCR). This method is employed for the detection of targeted DNA sequences (40-50 bp). Hybridization probes on the surface of the magnetically susceptible Fe microparticle recognize the target DNA sequence-specifically. The double-stranded DNA (dsDNA) microparticles are then quickly captured with a magnet from the sample matrix. This foregoes postpurification processes, such as electrophoresis, which make our technique time- and cost-effective. Captured dsDNA can be detected with intercalating dyes such as ethidium bromide through a loss in the UV absorption signal with a limit of detection (LOD) of 24 nM within 15 min. Likewise, surface-bound DNA can act as a primer in PCR to decrease the LOD to 5 pM within 2 h. This is the first instance of a nucleotide-modified magnetically susceptible carbon substrate that is PCR-compatible. Besides DNA capture, this strategy can eventually be applied to sequence-specific nucleic acid purification and enrichment, PCR cleanup, and single-strand generation. The DNA-coated particles are stable under PCR conditions (unlike commonly used polystyrene or gold particles).

Femtomolar endogenous adenosine triphosphate-responded photoelectrochemical biosensor based on Au@Cu2O core-shell nanocubes for the ultrasensitive determination of Escherichia coli O157:H7 in foods.

Sensitive and precise determination of virulent foodborne pathogens is significant for food safety. Herein, an ultrasensitive photoelectrochemical (PEC) bioanalysis was developed using the endogenous adenosine triphosphate (ATP)-responded Au@Cu2O core-shell nanocubes (Au@Cu2O NCs) to measure Escherichia coli O157: H7 (E. coli O157:H7) in food. Briefly, the phage-functionalized gold wire was used to specifically recognize the target pathogen. With the bacteriolysis of lysozyme, the endogenous ATP molecules were emitted from the captured target bacteria and enriched by another ATP aptamer-modified gold wire. Following the exchange with complementary DNA (cDNA) chains, the bonded ATP would be released. It could simultaneously etch the Au@Cu2O NCs and compete with external circuit electrons to combine photogenerated holes on the Au@Cu2O NCs-modified screen-printed electrode. With the synergy of the two signal amplification mechanisms, a significant attenuation of photocurrent signal appeared even with femtomolar ATP. Therefore, the purpose of ultrasensitive determination of E. coli O157:H7 was realized, which depended on the endogenous ATP rather than exogenous signal probes. The proposed biosensor presented a good analysis performance within 10-106 CFU/mL with a detection limit of 5 CFU/mL. Besides, its specificity, repeatability, and stability were also investigated and acceptable. The detection results for food samples matched well with the results detected by the plate counting method. This work gives an innovative and sensitive signal amplification strategy for PEC bioassays in foodborne pathogens detection.