Search

G-quadruplex (G4)/hemin DNAzyme is a promising candidate to substitute horseradish peroxidase in biosensing systems, especially for the detection of nucleic acids. However, the relatively suboptimal catalytic capacity limits its potential applications. This makes it imperative to develop an ideal signal for the construction of highly sensitive biosensing platforms. Herein, we integrated a novel chimeric peptide-DNAzyme (CPDzyme) with the ligase chain reaction (LCR) for the cost-efficient and highly sensitive detection of nucleic acids. By employing microRNA (miRNA) and single-nucleotide polymorphism detection as the model, we designed a G4-forming sequence on the LCR probe with a terminally labeled amino group. Subsequently, asymmetric hemin with carboxylic arms allowed assembly with the LCR products and peptide to form CPDzyme, followed by the magnetic separation of the extraneous components and chemiluminescence detection. Compared with the conventional G4/hemin signaling-based method, the LCR-CPDzyme system demonstrated 3 orders of magnitude improved sensitivity, with accurate quantification of as low as 25 aM miRNA and differentiation of 0.1% of mutant DNA from the pool containing a large amount of wild-type DNA. The proposed LCR-CPDzyme strategy is a potentially powerful method for in vitro diagnostics and serves as a reference for the development of other ligation- or hybridization-based nucleic acid amplification assays.

Low-voltage cables are extensively utilized in residential, commercial, and industrial fields, often arranged in clusters. However, inadequate heat dissipation and high load currents can result in high operating temperatures, accelerating insulation aging and leading to fire hazards. Traditional temperature measurement methods suffer from shortcomings, including contact tests, high cost, uncovered areas, and so on. To overcome these limitations, this article proposes a spatial temperature measurement method based on the electronic nose. The method involves capturing the responses of gas sensors to the decomposition gases emitted by the overheated cables. The response data are then processed using a transformer neural network to detect the temperature rise in the cable. An effective pretraining and fine-tuning paradigm is also employed to optimize the transformer network, enabling the algorithm to resist the influences of the external environment and the sensor drift. The prediction accuracy of this processing algorithm surpassed that of commonly used neural networks and traditional calibration methods. Throughout both the five-month timespan experiment and the high-current overheating experiment, the proposed method consistently demonstrated high-temperature prediction accuracy, thereby affirming its exceptional generalization performance.

Visually identifying the molecular changes in single cells is of great importance for unraveling fundamental cellular functions as well as disease mechanisms. Herein, we demonstrated a mass spectro-microtomography with an optimal voxel resolution of ∼300 × 300 × 25 nm3, which enables three-dimensional tomography of chemical substances in single cells. This mass imaging method allows for the distinguishment of abundant endogenous and exogenous molecules in subcellular structures. Combined with statistical analysis, we demonstrated this method for spatial metabolomics analysis of drug distribution and subsequent molecular damages caused by intracellular drug action. More interestingly, thanks to the nanoprecision ablation depth (∼12 nm), we realized metabolomics profiling of cell membrane without the interference of cytoplasm and improved the distinction of cancer cells from normal cells. Our current method holds great potential to be a powerful tool for spatially resolved single-cell metabolomics analysis of chemical components during complex biological processes.

Accelerating the charge transfer between electroactive species and the electrode is always a hot topic. Here, we report a finding of Ru(bpy)33+diffusion-induced acceleration of charge transfer from Ru(bpy)32+-doped silica nanoparticles (RDSNs) to the electrode via electrochemiluminescence (ECL) imaging at a single nanoparticle scale. Ru(bpy)32+in the electrolyte can act as an enhancer of RDSN ECL emission in the presence of coreactant tripropylamine, which amplifies the RDSN ECL by 478 times at 10 μM free Ru(bpy)32+. According to percolation theory, the diffusion of electro-generated Ru(bpy)33+near a single RDSN brings much quicker charge transfer to the electrode than electron hopping in RDSN, which is demonstrated by spatial and temporal interaction imaging of the RDSN and the Ru(III) diffusion layer. Taking advantage of this new mechanism, a real-time ECL imaging method has been constructed to monitor the rapid change of cell permeability during surfactant treatment.

SF6 decomposition products could reflect the running status and inner faults of power equipment, and it's expected to realize a timely warning. In this work, six faults including spark and corona discharge were simulated, and SF6 decomposition products with various types and contents were obtained as well. Different from previous investigations employing precision instruments, such as gas chromatography and infrared spectroscopy, a micro sensor array loaded with three gas-sensitive nanomaterials was used to discriminate fault characteristic gases, performing obvious advantages in small size, high integration, and rapid detection. Gas chromatography-mass spectrometry (GCMS) indicated that seven analytes had significant differences in types and contents. Meanwhile, the as-prepared micro gas sensor array also outputted significantly various signals for seven analytes, which provided a basis for gas identification. With the assistance of stacked denoising autoencoder (SDAE)-based discrimination algorithms, the recognition model between the response signals of the array and the discharge faults in power equipment could be established. In comparison with KNN (66.67 %), decision tree (70.47 %), and BPNN (73.33 %), SVM has achieved the highest average accuracy of 75.23 %. Totally, this work provides a promising novel method for rapid on-site inspection of SF6-insulated power equipment.

Most of the previous works used to improve the performance of single gas sensors by forming the array. However, more discrete sensors would bring higher costs, larger volumes, and power consumption. With the technique of micro-electro-mechanical systems (MEMS), a microchip with three sensitive materials (ZIF8-WO3, ZIF8-In2O3, and ZIF8-SnO2) has been fabricated to detect the mixtures of H2S and SO2. By combining the short-period thermal (SPT) modulation with the periodic sampling, the response curve could be split into several sub-curves, and each sub-curve was regarded as the virtual device operated at a constant temperature (CT). It can reduce power consumption without increasing the physical volume. Based on the fluctuation and distinction of the descriptors, the optimal 24 features were extracted from the initial 144 features. A stacked denoising autoencoder (SDAE) was employed to enhance the generalization ability of Bagging neural networks. Toward the unknown 30 mixtures of H2S and SO2, the recognition model under SPT, (78.67%) had better performance than that under CT, (62.67%). SPT (92.63%) has a smaller non-overlapping area of feature buffers than CT (50.45%), which might be the physics behind the performance improvement. Certainly, this work has broad application prospects in the future.

The outbreak of the pandemic caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) calls for an urgent unmet need for developing a facial and cost-effective detection method. The requirement of well-trained personnel and sophisticated instrument of current primary mean (reverse transcription polymerase chain reaction, RT-PCR) may hinder the practical application worldwide. In this regard, a reverse transcription recombinase polymerase amplification (RT-RPA) coupled with CRISPR-Cas12a colorimetric assay is proposed for the SARS-CoV-2 detection. The methodology we have described herein utilizes DNA-modified gold nanoparticles (AuNPs) as a universal colorimetric readout and can specifically target ORF1ab and N regions of the SARS-CoV-2 genome. After the virus genome is amplified through RT-RPA, the resulting abundant dsDNA will bind and activate Cas12a. Under trans-cleavage degradation, the capped DNA substrate will be hydrolyzed gradually from AuNPs, demonstrating a change in the surface plasmon resonance (SPR), which can be facially monitored by UV–vis absorbance spectroscopy and naked eye observation. The high amplification efficiency from RT-RPA and Cas12a trans-cleavage process bring the sensitivity of our method to 1 copy of viral genome sequence per test. Notably, under the dual variations inspecting from the isothermal amplification and Cas12a activation process, the false positive events from other beta coronavirus members can be effectively avoided and thus significantly improve the specificity. Furthermore, the reliability of this colorimetric assay is validated by standard clinical samples from the hospital laboratory department. Through integration of the inherently high sensitivity and specificity from an RPA-coupled Cas12a system with the intrinsic simplicity of AuNP-based colorimetric assay, our method increases the practical testing availability of SARS-CoV-2.

Among the various aflatoxin B1 (AFB1) assays, performing accurate detection is difficult because false positives and false negatives are frequent due to limited sensitivity, expensive equipment, or inadequate pretreatment during operation. Here, an “off–on” switch-type electrochemiluminescence (ECL) aptasensor armed with cobalt–sulfur quantum dots was encapsulated in hollow cobalt-layered double hydroxide nanocages as an enhanced luminescent probe (Co-LDH@QDs), and a ferrocene-modified aptamer (Fc-APT) was used as a luminescent quencher. In general, when Fc-APT was hybridized with complementary DNA modified with a DNA nanotetrahedron, electron transfer between ferrocene and Co-LDH@QDs was facilitated, leading to efficient quenching of the ECL intensity into an “off” state in the absence of AFB1. In the presence of AFB1, the intensity of ECL increased with an increasing AFB1 concentration after Fc-APT specifically recognized that AFB1 was detached from the electrode interface to achieve an “on” state. The linear range of the proposed ECL aptasensor for AFB1 detection was 0.1 pg mL–1to 10 ng mL–1, with a detection limit of 0.03 pg mL–1. We successfully employed the proposed ECL aptasensor for corn application, which provides an economical and simple alternative to complex and costly enzyme-linked immunoassays. The switch-type ECL aptasensor provides quick, accurate, and prospective technological support for pinpoint management of food safety.

Plant roots interact with diverse fungi that are essential for maintaining the productivity and sustainability of pasture ecosystems, but how these root-associated fungi (RAF) differ between forage species and how they respond to nutrient enrichment and fungicide application are not well understood. Here, we constructed an 11-year experiment involving fungicide application (with or without) nested within four levels of experimental nitrogen (N) addition treatments in an alpine pasture, and the RAF communities, root traits, tissue nutrients, and shoot biomass of two dominant forage species (Carex capillifoliaand Elymus nutans) were analyzed. The RAF community composition showed striking differences between the plant species and was strongly affected by both N addition level and fungicide applications. Fungicide, but not N application, dramatically reduced the RAF richness of all functional guilds in both plant species, and fungicide also simplified the co-occurrence network of the RAF for C. capillifolia. The RAF community correlated strongly with root traits, whereas their relationships became weakened or even vanished at the level of the individual plant species. The importance of RAF to plant nutrients and productivity varied between plant species, with significant contributions in C. capillifoliabut not in E. nutans. This is the first report elucidating the long-term effect of fungicides on RAF in alpine pastures, and our findings emphasize the host-specific responses of RAF community structure and function to anthropogenic disturbances.

The Great Wall of China was a military facility that has been continuously built and used for over thousands of years, and is a world-renowned cultural heritage site today. The plants growing on top surface of the Great Wall caused the damage of the Great Wall, but the process of removing these plants may further damage the body of the Great Wall. In this paper, based on the Analytic Hierarchy Process and the expert Delphi method, we selected 13 specific indices from three Constraint Layer factors, and then estimated and identified 45 species/categories of plants on top surface of the Dazhuangke section of the Great Wall. The results showthe constitution and the evaluation gradeof the evaluation system. The factor of Disruptive Effects plays the main guidance role in the evaluation system of the Constraint Layer; The indices of Impact on the Near Side Wall is the core element of the evaluation model with the highest weight of the Standard Layer. And the “Preservation”, “Partial Preservation”and “Removal” recommendations were given based on three evaluation grade (from Grade I to Grade III). This research provides scientific basis for the protective repair of the Great Wallheritage as well as "Garden on the Great Wall".

A sensitive and facile electrochemical sensor based on glassy carbon electrode (GCE) receiving electrochemical anodic pretreatment for signal amplification was developed for the determination of 3-nitrotyrosine (3-NT) (an oxidative stress biomarker). Adding sodium hexadecyl sulfate (SDS) to 0.1 M HNO3 solution was conducive to adsorption onto the surface of modified electrode, which promoted electron exchange and enhanced electrochemical behaviors by significantly increasing the hydrophobicity of electrode surface. Scanning electron microscopy showed that the surface of modified GCE had a remarkably thin layer composed of dense nanoparticles owing to surface layer oxidation, growth of graphite oxide thin layer and microscopic mechanical destruction of electrode surface during cyclic voltammetry by anodization oxidation. Under optimal conditions, the current change of 3-NT in square wave stripping voltammetry (SWV) was linearly related to its concentration in the range of 0.05[?]30.0 uM, with a detection limit (S/N = 3) of 17.0 nM, acceptable stability and reproducibility. Additionally, this sensor was successfully applied to detect 3-NT in human serum samples.

Self-enhanced electrochemiluminescence (ECL) can be achieved via the confinement of coreactants and ECL emitters in a single nanostructure. This strategy has been used for the design of anodic ECL systems with amine compounds as coreactants. In this work, a novel confinement system was proposed by codoping positively charged ECL emitter tris(2,2′-bipyridine)ruthenium(II) (Ru(bpy)32+) and negatively charged coreactant peroxydisulfate (S2O82–) in silica nanoparticles. The codoping process could be performed by introducing S2O82–in cationic poly(diallyldimethylammonium chloride) (PDDA) to form PDDA@S2O82–and then encapsulating it and Ru(bpy)32+in the Triton X-100 vesicle followed by the hydrolysis of tetraethyl ortosilicate, surface modification, and demulsification. The obtained RuSSNs exhibited good homogeneity, excellent monodispersity, acceptable biocompatibility, and 2.9-fold stronger ECL emission than Ru(bpy)32+-doped silica nanoparticles at an equal amount of nanoparticles in the presence of 0.1 M K2S2O8. Thus, an in situ self-sensitized cathodic ECL imaging method was designed for the monitoring of glycoprotein on living cell membranes. This work provides a new way for the modification, enhancement, and application of nano-ECL emitters in biological analysis.

A sensitive and facile electrochemical sensor based on glassy carbon electrode (GCE) receiving electrochemical anodic pretreatment for signal amplification was developed for the determination of 3-nitrotyrosine (3-NT) (an oxidative stress biomarker). Adding sodium hexadecyl sulfate (SDS) to 0.1 M HNO3solution was conducive to adsorption onto the surface of modified electrode, which promoted electron exchange and enhanced electrochemical behaviors by significantly increasing the hydrophobicity of electrode surface. Scanning electron microscopy showed that the surface of modified GCE had a remarkably thin layer composed of dense nanoparticles owing to surface layer oxidation, growth of graphite oxide thin layer and microscopic mechanical destruction of electrode surface during cyclic voltammetry by anodization oxidation. Under optimal conditions, the current change of 3-NT in square wave stripping voltammetry (SWV) was linearly related to its concentration in the range of 0.05∼30.0 μM, with a detection limit (S/N = 3) of 17.0 nM, acceptable stability and reproducibility. Additionally, this sensor was successfully applied to detect 3-NT in human serum samples.