Search

In this work, a new type of Au-tetrahedral DNA nanostructure (Au-TDN) was originally proposed and successfully applied in an electrochemiluminescence aptasensor to detect organophosphorus pesticides (Ops).

The massive use of organophosphorus pesticides (OPs) poses a great threat to food safety, human health and environmental protection. As there are many kinds of pesticides, their detection is facing a severe challenge. The simultaneous detection of multiple organophosphorus pesticides in one test is a problem to be solved at present. In this paper, a time-resolved fluorescent immunochromatographic (TRFIA) strip is prepared by using broad-specificity antibodies (Abs) of OPs as the recognition element. Abs were connected to europium oxide latex microspheres using sheep anti-mouse antibodies (SaMIgG) to form an indirect probe. This strategy could effectively realize signal amplification, and could save the amount and protect the activity of Abs. After the detection, the color change of the test line (T-line) was observed to make qualitative judgment under UV-light (365 nm). Then, the images of the positive sample were analyzed by using ImageJ to complete the quantitative detection. Under optimal construction and operating conditions, the limit of detection of the strip could reach 0.53 ng g

Background: Aedes albopictus is considered to be the main vector of dengue fever and Chikungunya fever in China. Mosquito control is an important component of the integrated programs to prevent dengue fever transmission. In this study, to provide technical support for future genetic control of mosquitoes, the genetic structure of Ae. albopictus population in China was analyzed and the correlation between genetic variations within Ae. albopictus population and kdr mutation was explored. Methods: Seventeen collection sites from 11 provinces (municipalities) of Ae. albopictus were collected from 2016 to 2021 in China, including most regions in the distribution area. Genomic DNA was extracted from individual adult mosquito using the DNAzol reagent. Eight microsatellite loci were finally selected for genotyping. Population genetic structure and demographic inference were analyzed using the software. Pearson correlation coefficient R was used to examine the association between the intra-population genetic variation and kdr mutation. Results: The considered eight microsatellite loci, scored in 453 mosquitoes across the 17 localities from North to South of China. The variation analysis showed that most variation occurred within individuals, whereas only about 9% of the total variation was detected among populations. Three gene pools were inferred by Bayesian analysis, in which the overall trend was that the northern populations belong to gene pool I (red), the eastern populations belong to III (blue), and the southern populations belong to three different gene pools. We also observed that the greater the genetic difference (FST), the lower the wild-type frequency of F1534 of VSGC gene in the same population. Conclusions: The degree of genetic divergence of Ae. albopictus in China was very low among the populations. These populations can be divided into three genetic gene pools. The gene pool of the northern and eastern Chinese populations was relatively simple, and southern populations were heterogeneous. The greater the genetic difference within the population, the larger the mutation rate of knockdown resistance, indicating that frequent migration among Ae. albopictus populations in China maybe a major factor in the increasing insecticide resistance.

Broad-spectrum antibodies can effectively recognize substances with similar structures and have broad application prospects in field rapid detection. In this study, broad-spectrum antibodies (Abs) against organophosphorus pesticides (OPs) were used as sensitive recognition elements, which could effectively recognize most OPs. Gold nanoparticles (AuNPs) have good biocompatibility. It combined with Abs to form a gold-labeled probe (AuNPs–Abs), which enhances the effective binding of antibodies to nanomaterials. Prussian blue (PB) was added to electrodeposition solution to enhance the conductivity, resulting in superior electrochemical performance. The AuNP–Abs–PB composite film was prepared by electrodeposition on the electrode surface to improve the anti-interference ability and stability of the immunosensor. Under the optimal experimental conditions, the immunosensor had a wide detection range (IC20–IC80: 1.82 × 10–3–3.29 × 104 ng/mL) and high sensitivity. Most importantly, it was simple to be prepared and could be used to detect multiple OPs.

In this paper, a dual-signal amplified electrochemical immunosensor for quantitative detection of capsaicinoids in serum was reported, which could be used to study the pharmacological properties of capsaicinoids. To improve the sensitivity of the immunosensor, the glassy carbon electrode was modified with Prussian blue-gold nanocomposites (PB-AuNPs) and thionine (TH). PB-AuNPs provided better electrical conductivity. At the same time, TH enhanced the stability of electron transfer, leading to superior electrochemical performance. Meanwhile, an excellent anti-capsaicinoids antibody (Ab) was used to ensure the sensitivity and specificity of the electrochemical immunosensor. The prepared immunosensor was tested using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Under the optimal conditions, the proposed immunosensor displayed a wide linear range from 0.01 to 1000 ng/mL with a detection limit of 0.01 ng/mL and showed good recoveries (85.12–104.25%) and high stability. Additionally, the immunosensor was successfully applied to monitor capsaicinoids in real serum samples.

An electrochemical tetrahedral APT biosensor (Au-TAN biosensor) was successfully constructed, which had a stable structure and excellent performance using tetrahedral DNA nanomaterials (TDN) and Au nanoparticles (AuNPs) for the detection of acetamiprid. Specifically, we designed a partial paired complementary DNA (cDNA) of acetamiprid aptamer and inserted the cDNA together with the acetamiprid aptamer into four single-stranded DNA sequences forming each side of the TDN, modifying AuNPs to increase the current signal intensity, to assemble the Au-TAN. This proposed aptasensor was compared with ssAPT aptasensor and tetrahedral APT nanostructures (TAN) aptasensor, respectively. The results showed that the performance of the designed aptasensor was better than those of the above two aptasensors. The detection limit of the aptasensor was calculated to be 0.077 pM (S/N = 3), which was far lower than that of other methods that we compared. Under optimized conditions, the proposed aptasensor showed a wide linear detection range from 0.1 pM to 10 nM. The Au-TAN biosensor opens up new ideas for the construction of aptasensors and provides a new method for detection of small molecular substances, such as pesticides residues.

The Hulun Buir sandy land in northern China is located at the northern limit region of the East Asian summer monsoon (EASM) and is therefore sensitive to the extension of the front of the rainfall belt. Here we report an n-alkane and compound-specific carbon isotope record from the Holocene sediments of Lake Yiheshariwusu in the middle of the Hulun Buir sandy land. The sediments contain a suite of n-alkanes with a strong odd over even carbon number predominance, with the maximum contribution from nC31, which is a typical distribution in grassland regions. The low temperatures in this cold region greatly limit the growth of C4 plants and thus the long-chain n-alkanes in lake sediments are mainly derived from leaf wax lipids of C3 plants growing within the sandy land. In this C3-vegetation-dominated region, the δ13C27–33 value (weighted carbon isotope values of nC27– nC33) are regulated mainly by the physiological and biochemical responses of plants to water stress and are therefore interpreted as a proxy of effective precipitation or humidity. The δ13C27–33 time series shows a trend of gradually decreasing values that suggests an increase in effective precipitation since 8.5 ka (1 ka = 1000 cal yr BP). Relative droughts occurred during the intervals of 6.3–5.5, 4.1–3.6 ka, and during the last 200 years. In addition, the δ13C27–33 time series and comparable paleoenvironmental records from neighboring sites suggest opposite trends of summer monsoon rainfall between northeastern and southeastern China. We suggest that a coupled process between low and high latitudes (the western Pacific Subtropical High and the Okhotsk High) may have played a fundamental role in regulating the shift of the frontal rainfall belt and monsoon rainfall distribution in eastern China during the Holocene.

The accurate identification of sandfly species is crucial because some species transmit medically significant diseases, including leishmaniasis, bartonellosis and sandfly fever. However, due to the high similarity of the external morphology in sandfly species, identification can only be performed using internal morphological characteristics after dissection, which is time consuming and requires highly experienced staff. Thus, the introduction of suitable molecular markers may solve these identification problems. This study screened suitable DNA barcodes to identify common sandfly species in China. The phlebotomine sandflies were collected from Sichuan, Henan and Hainan Provinces from 2014 to 2016. The species were identified by the morphological characteristics of the pharyngeal armature and spermatheca. The genomic DNA of sandfly was extracted individually, and mitochondrial DNA (mtDNA) cytochrome C oxidase subunit I (COI) and cytochrome B (Cytb) as well as the 18S subunit of ribosomal DNA (rDNA) were amplified using polymerase chain reaction (PCR). Additionally, intraspecific and interspecific differences (p-distance) were calculated to evaluate the feasibility of the three gene fragments as a DNA barcode. The phylogeny trees of all sandfly species in this study were constructed using neighbor joining (NJ) method. Six species were identified by the morphological features, belonging to Phlebotomus and Sergentomyia, as Ph. chinensis s. l., Ph. stantoni, Se. bailyi, Se. iyengari, Se. squamirostris, and Se. squamipleuris. Analysis based on three gene fragments revealed some degree of intraspecific polymorphism among these sandfly species in China. The largest intraspecific variation occurred in Ph. chinensis s. l. (mtDNA COI, p-distance = 0.042; mtDNA Cytb, p-distance = 0.071), but the 18S rDNA fragment showed a small variation (p-distance = 0.005). The ranges of interspecific p-distances for mtDNA COI and mtDNA Cytb were 0.138 - 0.231 and 0.128 - 0.274, respectively. However, the interspecific p-distances of 18S rDNA are relatively low ranging from 0.003 to 0.055. Both mitochondrial COI and Cytb gene fragments are valid molecular identification markers in theses sandfly species. The topological structure of phylogeny trees based on mtDNA COI, mtDNA Cytb and 18S rDNA genes were all consistent with morphological classification. And we also found there were significant intraspecies differences within Ph. chinensis s. l. (0.006-0.071) and Se. bailyi (0.002-0.032) based on mtDNA Cytb gene fragment. Sequence alignment data suggested that Ph. chinensis s. l. from Sichuan should be Ph. sichuanensis, and the sandfly specimen collected from Henan was Ph. chinensis s. s.. There could be cryptic species in Se. bailyi from China.

In this research, an electrochemical aptamer sensor based on the specific recognition of tetracycline, doxycycline and oxytetracycline was developed through flower-like zinc oxide/reduced graphene oxide/nano-gold composites. Firstly, floral zinc oxide had a large contact area, which bound more gold nanoparticles, and bound more adapters through Au–S bonds. Next, due to the poor conductivity of floral zinc oxide, the combination of floral zinc oxide and rGO was able to improve the conductivity. Finally, the rGO–ZnO–AuNPs composite was used as a platform to improve the electron transport rate on the glassy carbon electrode surface, enhance the electrochemical strength, and provide enough active sites for the capture of aptamers. After condition optimization, the lowest detection concentrations for tetracycline, doxycycline and oxytetracycline were 0.33, 0.28 and 0.3 ng·ml−1 respectively. In addition, this aptasensor had good stability, selectivity, anti-interference and reproducibility. It would be further applied to the detection of antibiotics in milk.

It is well known that Arctic sea ice and Arctic amplification have played an important role in recent climate change in middle to high latitudes of the Northern Hemisphere. We present a high‐resolution elemental data set, spanning the past 9,000 years, obtained using in‐situ synchrotron radiation X‐ray fluorescence measurements of a lake sediment core from Lake Shuang in the Altai Mountains. Based on calibration against the local instrumental climatic record, the Rb/Sr ratio of the sediments is interpreted as an indicator of weathering intensity, which is related to precipitation and temperature variations. There is very little bromine in the granites and moyites in the catchment of Lake Shuang, and the sedimentary Br is derived primarily from wet deposition originating from precipitation and enriched by biogenic processes in this open lake system. The Br variation is positively correlated with local precipitation. The Rb/Sr and Br time series show distinct decadal‐scale to millennial‐scale cycles that are similar to those of Arctic sea‐ice variations, which implies the important role of Artic sea ice in modulating environmental change at Lake Shuang. Our results support a previous suggestion that sea ice loss would cause an increase in atmospheric water vapor content in the Arctic, resulting in the frequent incursion of cold air masses from the Arctic into middle latitudes, and leading to increased snow cover and precipitation, and vice versa.

Over the past decades, due to the desire for artificial umami flavors, apparatuses for detecting the umami taste have constantly been developed. Nevertheless, most information on umami is still acquired through human sensory assessment, which makes it difficult to establish an umami standard or quantify the umami flavor. In this study, the ligand binding domain called venus flytrap (VFT) domain of the umami taste receptor protein T1R1 was used as a recognition element, and an electrochemical biosensor based on a double-signal amplification strategy was constructed using single-walled carbon nanotubes (SWCNTs) and Prussian blue (PB). Moreover, the umami taste of four representative umami substances, inosine-5′-monophosphate (IMP), monosodium L-glutamate (MSG), beefy meaty peptide (BMP), and sodium succinate (WSA), were successfully quantitatively measured using differential pulse voltammetry (DPV) at an electrochemical workstation. Based on an equation (S/N = 3), the low detection limits (LODs) of IMP, MSG, BMP, and WSA were 0.1, 0.1, 0.1, and 0.01 pM, respectively. Meanwhile, a normalized signal intensity of more than 90% was kept for 4 days. The results showed that the biosensor could be used to detect umami substances with high sensitivity and selectivity, and was shown to have human-like performance. To develop the T1R1-VFT biosensor using the above-mentioned method, we utilized the ligand binding domain of the human umami receptor, rather than the entire umami receptor protein, which had a complex structure, having the following advantages: volume reduction, simplicity, and stability. This method has great potential for the detection of umami tastes, instead of using sensory evaluation, and for the development of new artificial flavorings.

Immunoassay has the advantages of high sensitivity, high specificity, and simple operation, and has been widely used in the detection of mycotoxins. For several years, time-resolved fluorescence immunochromatography (TRFIA) paper-based sensors have attracted much attention as a simple and low-cost field detection technology. However, a traditional TRFIA paper-based sensor is based on antibody labeling, which cannot easily meet the current detection requirements. A second antibody labeling method was used to amplify the fluorescence signal and improve the detection sensitivity. Polystyrene fluorescent microspheres were combined with sheep anti-mouse IgG to prepare fluorescent probes (Eu-IgGs). After the probe fully reacted with the antibody (Eu-IgGs-Abs) in the sample cell, it was deployed on the paper-based sensor using chromatography. Eu-IgGs-Abs that were not bound to the target were captured on the T-line, while those that were bound were captured on the C-line. The paper-based sensor reflected the corresponding fluorescence intensity change. Because a single molecule of the deoxynivalenol antibody could bind to multiple Eu-IgGs, this method could amplify the fluorescence signal intensity on the unit antibody and improve the detection sensitivity. The working standard curve of the sensor was established under the optimum working conditions. It showed the lower limit of detection and higher recovery rate when it was applied to actual samples and compared with other methods. This sensor has the advantages of high sensitivity, good accuracy, and good specificity, saving the amount of antibody consumed and being suitable for rapid field detection of deoxynivalenol.

In this work, an ultrasensitive and selective electrochemiluminescence (ECL) aptasensor with Au-tetrahedral aptamer nanostructure (Au-TAN) for acetamiprid detection was developed, which employed luminescence property of luminol and hydrogen peroxide (H2O2) as a co-reactant to apply the prepared Au-TAN to the luminescence systems. Au-TAN was prepared to modify an electrode surface via an Au-S bond to form a stable tetrahedral nanostructure. Fixed on the surface of the working electrode, Au-TAN could not only enhance the function of the aptamer but also boost the sensing performance. At the same time, Au nanoparticles (AuNPs) of the Au-TAN could also catalyze H2O2, thereby enhancing the luminescence performance of this aptasensor. The pH of the buffer solution, the concentration of H2O2 and the concentration of Au-TAN were optimized. Under the optimal conditions, the aptasensor had a detection limit of 0.0576 pM (S/N = 3), which was lower than those of other aptasensors for acetamiprid detection. Moreover, the weak alkaline environment explored in the experiment could expand its application range. Above all, the proposed method presented a high accuracy and sensitivity.

This work demonstrates the sensitive amperometric determination of organophosphorus pesticides (OPs) on screen-printed electrodes (SPEs) modified with antimony tin oxide-chitosan (ATO-CS) and ordered mesoporous carbon-chitosan (OMC-CS) composite nanomaterials. ATO could effectively promote electron transfer and enhance the electrochemical reaction. OMC had a larger specific surface area, so it could effectively fix more AChE and improve the sensitivity of the sensor. Thus, ATO-CS and OMC-CS were modified onto the SPE layer-by-layer, which could improve the electrochemical response, increase the fixed amount of the enzyme on the electrode, and, accordingly, the sensitivity of the biosensor was obviously improved. The electrochemical behavior of the AChE biosensor was studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. Under optimum conditions, with chlorpyrifos and methamidophos as the model compounds, the inhibition of AChE activity based on OPs was detected. The proposed acetylcholinesterase biosensor displayed an excellent analytical performance with great reproducibility. The detection limits for chlorpyrifos and methamidophos were 0.01 μg L−1 and 1 μg L−1, respectively. In addition, the as-prepared acetylcholinesterase biosensor was successfully utilized for the determination of OPs in actual samples.

The adulteration of edible vegetable oil is a serious threat to the health of consumers. Previous studies have shown that capsaicinoids could be used as a marker of adulteration to identify vegetable oils. The key sites of antibody and capsaicinoids were analyzed by computer aided molecular modeling (CAMM), which provided a basis for the selection of modified material and the implanting of antigen and antibody on the electrode in the subsequent construction of the electrochemical immunosensor. Simultaneously, it was determined that the different forces between capsaicinoids and antibody were the important reason for the differences in sensitivity of capsaicinoids. On this basis, combined with the good conductivity and excellent redox characteristic of Fe3O4NPs@CeO2, a competitive immunosensor was constructed. Under the optimal conditions, the proposed immunosensor provided a linear range of 10–3 to 104 ng ml−1 with a detection limit of 0.33 pg ml−1. This study may broaden the interaction between capsaicinoids and antibody, encourage the design of novel performance-enhanced antibody, and provide a new method for the detection of capsaicinoids.

In order to solve the problem that the sensor cannot be reused due to the passivation of the electrode surface, a refreshable electrochemical aptasensor based on a hydrophobic electrode and a magnetic nanocomposite had been developed. Therein, the hydrophobic electrode was formed by modifying a screen-printed carbon electrode (SPCE) with polydimethylsiloxane (PDMS), which could avoid adsorption of molecules on the electrode surface due to its hydrophobicity. Combined with aptamer (Apt), the synthesized graphene oxide-ferroferric oxide (GO-Fe3O4) was used as a magnetic catcher to capture specific organophosphorus pesticides (OPs), which could be removed to the working area of SPCE with a magnet for electrochemical detection. The performance analysis of hydrophobic electrode showed that the SPCE could be used twice. When the electrochemical signals of Apt/GO-Fe3O4 and OPs/Apt/GO-Fe3O4 were recorded using the same SPCE, the current differences between them were directly related to the concentrations of OPs. Through the contrast test between the spiked vegetable samples and the OPs standard solutions, it was found that the OPs concentrations could be qualitatively evaluated by comparing the current differences. At the same time, the characteristic of collecting target with magnetic catcher was helpful for detecting OPs with a low concentration. Therefore, the refreshable aptasensor provided a huge potential to small molecule target evaluation.

Asian aridification during the Cenozoic was strongly related to moisture flux modulated by sea incursion and the retreat fluctuations of the proto-Paratethys Sea via the Westerlies. However, the extents of the sea incursions are poorly constrained, and there is a lack of sedimentary records beyond the Central Asian basins. The Middle to Late Cretaceous Simao Basin and the Khorat Plateau in Southeast Asia contain thick continental sequences of red beds, evaporites, and aeolian deposits, but whether the depositional environment of the evaporites was marine or continental has been hotly debated. In this study, we compiled multiple sedimentology proxies, biomarkers, element geochemistry, and isotopic geochemistry of the fine-grained sediments of the Mohan section in the Simao Basin. Sedimentological analyses show that this section is composed of subtidal flat fine-grained siliciclastic and carbonate rocks and supratidal flat conglomerates and evaporites. The paleosalinity proxies show that the B concentration and B/Ga and Srcorrected/Ba ratios range from 30.3 to 81.7 ppm, 2.4 to 5.0, and 0.05 to 0.60, respectively, which indicate brackish conditions. The two typical increases in these proxies are consistent with the stratigraphic horizons of the diagnostic marine biomarkers 24-n-propyl- and 24-iso-propylcholestanes, which suggests seawater recharge. The carbonate δ13C and δ18O values (−4.84‰ to −1.75‰ and −8.25‰ to −3.69‰, respectively) and the bulk δ13Corg values (−26.5‰ to −23.22‰) also indicate the influence of seawater. We propose that the seawater likely originated from the proto-Paratethys Sea during a marine incursion. We propose for the first time that the proto-Paratethys seawater incursions extended into the Simao Basin and the Khorat Plateau. These results provide a novel paleogeographic configuration for East Asia during the Middle to Late Cretaceous. The retreat of the proto-Paratethys Sea, the northeast Trade Winds, and the tectonic uplift dramatically decreased the moisture and intensified the extreme aridification in the Simao Basin and the Khorat Plateau.