The self-powered electrochemical sensor has gained big achievements in energy and devices, but it is challenging in analytical application owing to its low energy conversion efficiency and limited ...selectivity caused by the plentiful interference in actual samples. Herein, a new self-powered biosensor was constructed by the integration of a photocatalytic fuel cell (PFC) with a molecular imprinting polymer (MIP) to achieve sensitive and specific detection of aflatoxin B1 (AFB1). Compared with other fuel cells, the PFC owns the advantages of low cost, high energy, good stability, and friendly environment by using light as the excitation source. MoS2–Ti3C2T x MXene (MoS2–MX) served as the photoanode material for the first time by forming a heterojunction structure, which can enhance the photocurrent by about 3-fold and greatly improve the photoelectric conversion efficiency. Aiming at the poor selectivity of the self-powered sensor, the MIP was introduced to achieve the specific capture and separation of targets without sample pretreatment. Using the MIP and PFC as recognition and signal conversion elements, respectively, the proposed self-powered biosensor showed a wide dynamic range of 0.01–1000 ng/mL with a detection limit of 0.73 pg/mL, which opened opportunities to design more novel self-powered biosensors and promoted its application in food safety and environmental monitoring.
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IJS, KILJ, NUK, PNG, UL, UM
Accurate quantification of moisture content redistribution and physical property change due to freeze–thaw is important for understanding frost heave and thaw settlement of fine-grained soils ...including clay. This paper presents 3D X-ray Computed Tomography (CT) data for a clay specimen before and after freeze–thaw and physical property data obtained by conventional laboratory testing, and the relationship among the date sets. Undisturbed clay specimens were subject to one-directional freeze–thaw in a closed system under different freezing temperatures to collect 3D X-ray CT images, and the variation in CT image intensity (CTI) before and after freeze–thaw were analyzed to reveal the spatial effects of freeze–thaw. Meanwhile, soil properties including moisture content, void ratio, and dry density were obtained for samples taken from different heights of the specimens with and without freeze–thaw to obtain their changes. Close correlations were observed between the physical property changes and the CTI variation. Linear equations were established between the changes of physical properties and the CTI variation. These equations could potentially be applied for high-resolution quantitative assessment of soil physical property changes due to freeze–thaw by using 3D X-ray CT. This study demonstrates that, compared with traditional test methods, CT scanning can be advantageous in revealing the internal change in soil physical properties due to freeze–thaw quantitatively and nondestructively.
•Proposed procedures for correcting the cupping and end effects•3D X-ray CT effective in revealing spatial structural change within clay•Close correlation between changes in CT intensity and physical properties•Establish linear equations for high resolution quantitative assessment of physical properties
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Nitromethane (CH3NO2) is an important organic chemical raw material with a wide variety of applications as well as one of the most common pollutants. Therefore it is pretty important to establish a ...simple and sensitive detection method for CH3NO2. In our study, a novel amperometric biosensor for nitromethane (CH3NO2) based on immobilization of electrochemically-reduced graphene oxide (rGO), chitosan (CS) and hemoglobin (Hb) on a glassy carbon electrode (GCE) was constructed. Scanning electron microscopy, infrared spectroscopy and electrochemical methods were used to characterize the Hb-CS/rGO-CS composite film. The effects of scan rate and pH of phosphate buffer on the biosensor have been studied in detail and optimized. Due to the graphene and chitosan nanocomposite, the developed biosensor demonstrating direct electrochemistry with faster electron-transfer rate (6.48s−1) and excellent catalytic activity towards CH3NO2. Under optimal conditions, the proposed biosensor exhibited fast amperometric response (<5s) to CH3NO2 with a wide linear range of 5μM~1.46mM (R=0.999) and a low detection limit of 1.5μM (S/N=3). In addition, the biosensor had high selectivity, reproducibility and stability, providing the possibility for monitoring CH3NO2 in complex real samples.
•Graphene was produced by electrochemical reduction, which is green and efficient.•A biosensor based on electrochemically-reduced GO, CS and Hb was constructed.•The biosensor had a wide linear range of and a low detection limit for CH3NO2 detection.•The biosensor has been applied in real samples, with high selectivity and stability.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Fe@Pt core–shell nanoparticles were synthetized by spontaneous replacement reaction, using Vulcan XC-72 carbon as support. The physical properties of the obtained Fe@Pt/C nanocomposites were ...characterized by X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy, and the electrocatalytic performances of the Fe@Pt/C were evaluated by cyclic voltammetry and chronoamperometry. Compared with the Pt/C, the Fe@Pt/C exhibited preferable electrocatalytic activity towards the reduction of hydrogen peroxide, and the oxidation of glucose and formaldehyde. Amperometric sensing of hydrogen peroxide was linear to its concentration in the range from 2.5μM to 41.605mM, with a detection limit of 750nM (S/N=3) and a sensitivity of 218.97μA mM−1 cm−2. At the same time, the sensor based on Fe@Pt/C showed a linear response range of 1–16mM glucose, and of 12.5μM–15.4mM formaldehyde, with high sensitivities of 11.75μA mM−1 cm−2 and 40.18μA mM−1 cm−2, respectively.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Seed dormancy is an important economic trait for agricultural production. Abscisic acid (ABA) and Gibberellins (GA) are the primary factors that regulate the transition from dormancy to germination, ...and they regulate this process antagonistically. The detailed regulatory mechanism involving crosstalk between ABA and GA, which underlies seed dormancy, requires further elucidation. Here, we report that ABI4 positively regulates primary seed dormancy, while negatively regulating cotyledon greening, by mediating the biogenesis of ABA and GA. Seeds of the Arabidopsis abi4 mutant that were subjected to short-term storage (one or two weeks) germinated significantly more quickly than Wild-Type (WT), and abi4 cotyledons greened markedly more quickly than WT, while the rates of germination and greening were comparable when the seeds were subjected to longer-term storage (six months). The ABA content of dry abi4 seeds was remarkably lower than that of WT, but the amounts were comparable after stratification. Consistently, the GA level of abi4 seeds was increased compared to WT. Further analysis showed that abi4 was resistant to treatment with paclobutrazol (PAC), a GA biosynthesis inhibitor, during germination, while OE-ABI4 was sensitive to PAC, and exogenous GA rescued the delayed germination phenotype of OE-ABI4. Analysis by qRT-PCR showed that the expression of genes involved in ABA and GA metabolism in dry and germinating seeds corresponded to hormonal measurements. Moreover, chromatin immunoprecipitation qPCR (ChIP-qPCR) and transient expression analysis showed that ABI4 repressed CYP707A1 and CYP707A2 expression by directly binding to those promoters, and the ABI4 binding elements are essential for this repression. Accordingly, further genetic analysis showed that abi4 recovered the delayed germination phenotype of cyp707a1 and cyp707a2 and further, rescued the non-germinating phenotype of ga1-t. Taken together, this study suggests that ABI4 is a key factor that regulates primary seed dormancy by mediating the balance between ABA and GA biogenesis.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
In this work, an innovative aptasensor based on electrochemiluminescence resonance energy transfer (ECL-RET) from CdTe quantum dots (QDs) to a cyanine dye (Cy5) fluorophore for the determination of ...Ochratoxin A (OTA) was fabricated. A strong cathodic ECL emission was obtained by the CdTe QDs modified glassy carbon electrode (GCE). After the immobilization with the capture DNA (cDNA) and the sequential hybridization with the probe DNA-modified Cy5 (pDNA, the aptamer of OTA), the ECL signal enhanced obviously through the ECL-RET. Meanwhile, the spectrum- and distance-related ECL enhancement effect was investigated. When the target OTA was in the presence, the pDNA-Cy5 molecules were released from the electrode surface owing to the specific interaction between OTA and aptamer, resulting in an evident decrease of ECL signal. Under optimal conditions, the developed aptasensor displayed the linear response toward OTA in the wide range of 0.0005–50 ng/mL with a low detection limit of 0.17 pg/mL. With the excellent selectivity, stability and repeatability, the strategy provided an efficient and universal method for the sensitive detection of target in practical application.
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•A simple and convenient aptasensor for OTA was prepared.•The ECL-RET aptasensor based on CdTe QDs and Cy5 has high sensitivity.•This sensor has a good specificity since the great affinity of aptamer to target.•The aptasensor could be applied to detect OTA in corn.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
A novel electrochemical aptamer biosensor was designed based on the signal amplification of gold nanoparticles (AuNPs) for the detection of a tumor biomarker, carcinoembryonic antigen (CEA). The ...electrochemical biosensor was constructed by sandwiching the CEA between an Au electrode modified with thiol-terminated CEA aptamer-1 (Apt1) and the AuNPs with thiol-terminated CEA aptamer-2 (Apt2) and 6-ferrocenyl hexanethiol (Fc). Amperometric detection of Fc by differential pulse voltammetry (DPV) on the electrochemical biosensor was used to quantify the concentration of CEA. The biosensor provided a linear range from 1 to 200ng/mL for CEA with a detection limit of 0.5ng/mL. Its performance was successfully evaluated with human serum spiked with CEA, indicating that the aptasensor has great potential for practical application. In addition, the electrochemical biosensor exhibited excellent selectivity responses and good stability toward the target analyte.
•A novel electrochemical aptasensor for the determination of CEA was developed.•Fc capped AuNPs–Apt2 conjugates were prepared for the signal amplification.•The electrochemical aptasensor showed a low background signal.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
A novel platform based on a hairpin oligonucleotide (HO) switch, gold nanoparticles (AuNPs), and enzyme signal amplification for the ultrasensitive detection of mucin 1 protein (MUC1) was developed ...in this assay. This HO aptamers and horseradish peroxidase (HRP) were immobilised on the AuNPs to yield HO-AuNP-HRP conjugates. AuNPs were used as labels and bridges between the HO and HRP. HRP was also used as label for catalysing the oxidation of o-phenylenediamine by H2O2. The reaction product was 2,3-diaminophenazine (DAP), which was reduced and could be detected at surface of modified electrode. The reduction signal of DAP was used as a probe for the sensitive detection. After the recognition between oligonucleotide and MUC1, biotin was exposed. Biotin, along with the conjugate, was captured by streptavidin onto the surface of modified electrode. Therefore, the detection of target MUC1 which was a membrane-associated glycoprotein of the mucin family could be sensitively transduced via detection of the electrochemical reduction signal of DAP. Compared to other aptasensors, this biosensor has a good linear correlation ranges from 8.8 nM to 353.3 nM and a lower detection limit of 2.2 nM for MUC1. The proposed method provided a new electrochemical approach for the detection of MUC1.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The outbreak of H9N2 avian influenza virus (H9N2 AIV) brings high mortality and huge economic losses every year. Sensitive and reliable detection methods are essential to timely diagnosis and ...treatment. Herein, a dual-modality immunoassay is proposed for H9N2 AIV detection by employing fluorescent-magnetic-catalytic nanospheres (FMCNs) as labels and alkaline phosphatase (ALP)-induced metallization as a signal amplification strategy. The excellent magnetic properties of FMCNs endow the assay a potential application in complex samples. Also, the excellent fluorescence properties of FMCNs enable fluorescence modality readout. The antibodies on the FMCN surface can achieve efficient capture and separation of targets. Amplified electrochemical modality readout can be obtained through ALP-catalyzed silver deposition. Dual-modality immunoassay combined the advantages of electrochemical assay with fluorescence assay and provides accurate detection results to meet different testing needs. With two quantitative analysis forms, H9N2 AIV can be detected by electrochemical signals with a quantitation range of 0.1 to 1000 ng/mL and a detection limit of 10 pg/mL. The linear range is 300 to 1000 ng/mL with a detection limit of 69.8 ng/mL by the fluorescence signal readout. Moreover, the specificity, anti-interference ability, accuracy, and diversity of the proposal have unlimited potential for early diagnosis of suspect infections.
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IJS, KILJ, NUK, PNG, UL, UM
Electrochemiluminescence (ECL) detection has attracted increasing attention as a promising analytical approach. A considerable number of studies showed that ECL intensity can be definitely improved ...by resonance energy transfer (RET), while the RET efficiency is strongly dependent on the distance between exited donors and acceptors. Herein we disclose for the first time a highly enhanced RET strategy to promote the energy transfer efficiency by coencapsulating the donor (Ru(bpy)32+)/acceptor (CdTe quantum dots, CdTe QDs) pairs into a silica nanosphere. Plenty of Ru(bpy)32+ and CdTe QDs closely packed inside a single nanosphere greatly shortens the electron-transfer path and increases the RET probability, therefore significantly enhancing the luminous efficiency. Further combining with molecularly imprinting technique, we develop a novel ECL sensor for ultrasensitive and highly selective detection of target molecules. Proof of concept experiments showed that extremely low detection limits of subfg/mL (S/N = 3) with broad linear ranges (fg/mL to ng/mL) could be obtained for detection of two kinds of mycotoxins (α-ergocryptine and ochratoxin A) that are recognized as potential health hazards at very low concentrations. This strategy combining enhanced RET system and molecularly imprinting technique, represents a versatile ECL platform toward low-cost, rapid, ultrasensitive, and highly selective detection of target molecules in diverse applications.
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IJS, KILJ, NUK, PNG, UL, UM
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