Kiwi-Inspired Rational Nanoarchitecture with Intensified and Discrete Magneto-Fluorescent Functionalities for Ultrasensitive Point-of-Care Immunoassay.

Fluorescent lateral flow immunoassays (FLFIA) is a well-established rapid detection technique for quantitative analysis. However, achieving accurate analysis of biomarkers at the pg mL-1 level using FLFIA still poses challenges. Herein, an ultrasensitive FLFIA platform is reported utilizing a kiwi-type magneto-fluorescent silica nanohybrid (designated as MFS) that serves as both a target-enrichment substrate and an optical signal enhancement label. The spatially-layered architecture comprises a Fe3O4 core, an endocarp-fibers like dendritic mesoporous silica, seed-like quantum dots, and a kiwi-flesh like silica matrix. The MFS demonstrates heightened fluorescence brightness, swift magnetic response, excellent size uniformity, and dispersibility in water. Through liquid-phase capturing and fluorescence-enhanced signal amplification, as well as magnetic-enrichment sample amplification and magnetic-separation noise reduction, the MFS-based FLFIA is successfully applied to the detection of cardiac troponin I that achieved a limit of detection at 8.4 pg mL-1, tens of times lower than those of previously published fluorescent and colorimetric lateral flow immunoassays. This work offers insights into the strategic design of magneto-fluorescent synergetic signal amplification on LFIA platform and underscores their prospects in high-sensitive rapid and on-site diagnosis of biomarkers.

Gold-Silver Alloy Nanoparticle-Incorporated Pitaya-Type Silica Nanohybrids for Sensitive Competitive Lateral Flow Immunoassay.

Although the competitive lateral flow immunoassay (CLFIA) using gold nanoparticles (AuNPs) as labels has been widely adopted for the rapid detection of small molecules, its sensitivity is often constrained by the insufficient colorimetric signal produced by conventional AuNPs labels. Herein, we introduce a new type of intensified colorimetric label, denoted as SAAS, which is engineered by integrating gold-silver alloy nanoparticles (Au-Ag NPs) within a dendritic silica scaffold. These pitaya-type silica nanohybrids combine the advantages of the amplified molar extinction coefficient of alloy units with the signal collective effect of numerous Au-Ag NPs in a singular label. The SAAS-based CLFIA strips not only achieve qualitative screening of aflatoxin B1 (AFB1) at an extraordinarily low concentration of 0.2 ng/mL by the naked eye but also enable precise AFB1 quantification through a smartphone, with a remarkable limit of detection of 0.00314 ng/mL. Moreover, by leveraging SAAS as a quencher, we have delved into transforming the conventional signal-off mode of competitive immunoassay into a signal-on configuration. This innovation led to the development of a fluorescent LFIA that augments interpretative precision and sensitivity. Our study demonstrates the substantial potential of the proposed nanohybrid labels in enhancing the sensitivity of CLFIA for detecting small molecules.

Leak Detection and Localization in Multi-Grid Space Using Improved Gaussian Plume Model.

Leak detection and localization of liquid or gas is of great significance to avoid potential danger and reduce the waste of resources. Leak detection and localization methods are varied and uniquely suited to specific application scenarios. The existing methods are primarily applied to conventional pressurized pipelines and open areas, and there are few methods suitable for multi-grid spaces. In this paper, a gas diffusion model applied to multi-grid space is constructed, and a method for leak detection and localization using the concentration gradient of characteristic gas is proposed according to the prediction behavior. The Gaussian plume model is selected due to its advantages of simplicity and the interpretation of gas diffusion behavior is closer to reality; the expression of the improved model is also obtained. To verify the correctness of the model and the applicability of the localization method, taking the coolant leakage in the circuit system as an example, three experiments with different source strengths were repeated. The fitting correlation coefficients between the gas concentration data of the three experiments and the model are 0.995, 0.997 and 0.997, respectively. The experimental results show that the model has a strong correlation with the real plume behavior, and it is reasonable to use the gas concentration gradient for the localization of the leak source. This study provides a reference for future research on the leak detection and localization of gas- or liquid-containing volatile substances in a complex multi-grid space.

Ultrasensitive Competitive Lateral Flow Immunoassay with Visual Semiquantitative Inspection and Flexible Quantification Capabilities.

Antibiotics abuse has caused various problems threatening human health and ecological environment. Monitoring antibiotics residual levels is of great significance, yet still challenging for quantitative point-of-need testing with high-sensitivity and visual capability. Here we developed a competitive lateral flow immunoassay (CLFIA) platform with flexible readout for enrofloxacin (ENR), a regularly added antibiotic. To overcome the limitation of low sensitivity of traditional colloidal gold-based CLFIA, the three-dimensionally assembled gold nanoparticles (AuNPs) within dendritic silica scaffold were fabricated as signal reporters. The assembly structure effectively retained the intrinsic absorption features of hydrophobic AuNPs and greatly enhanced the light extinction ability of a single label for signal amplification. The obtained CLFIA strips can not only achieve qualitative screening of ENR at a very low concentration by naked eye (cutoff value: 0.125 ng/mL), but also enable ultrasensitive quantification of ENR by an optical scanner (limit of detection: 0.00195 ng/mL) or a smartphone (limit of detection: 0.0078 ng/mL). Moreover, to elaborate the visual inspection degree of CLFIA against traditional yes/no interpretation, a novel multirange gradient CLFIA strip was prepared for visually semiquantitative identification of ENR with four concentration ranges. The novel CLFIA platform demonstrated sensitive, specific, and reliable determination of ENR with flexible signal readout and provides a potential and invigorating pathway to point-of-need immunoassay of antibiotics.

Hue Recognition Competitive Fluorescent Lateral Flow Immunoassay for Aflatoxin M1 Detection with Improved Visual and Quantitative Performance.

Immunological detection of small molecules in a point-of-care (POC) format is of great significance yet remains challenging for accurate visual discrimination and quantitative analysis. Here, we report a novel hue recognition competitive fluorescent lateral flow immunoassay (HCLFIA) strip that allows both visual and quantitative detection of aflatoxin M1 (AFM1). The HCLFIA strip works on the basis of the ratiometric change of emission, arising from the overlap of fluorescence signals of two nanocomposites tagged with probe antibodies and coated antigens. A visually discernible orange-red-to-green fluorescence color change allows the naked eye semiquantitative readout of AFM1 around the threshold concentration (0.05 ng mL-1), yielding a visible detection limit of 0.02 ng mL-1. Moreover, using a custom smartphone-based device and color chart analysis, ultrasensitive quantitative detection of AFM1 can be achieved with a low limit of detection at 0.0012 ng mL-1, which is considerably better than those of the previously reported colorimetric and fluorescent strips. The accuracy performed in spiked milk samples ranged from 97.91 to 113.12% with a coefficient of variation below 7.8%, showing good consistency with the results from isotope dilution liquid chromatography-tandem mass spectrometry. Thanks to the unique hue recognition scheme, the HCLFIA strip holds great potential for POC detection of small molecules.

Ratiometric fluorometric and visual determination of cyanide based on the use of carbon dots and gold nanoclusters.

An optical method is described for the ratiometric fluorometric determination of cyanide ions. It is based on the use of a mixture of aqueous solutions of blue-emitting carbon dots (CDs) and red-emitting gold nanoclusters (AuNCs). The presence of cyanide reduces the red fluorescence of the AuNCs through the formation of a stable complex [Au(CN)2-]. The blue emission of the CDs, in contrast, stays constant. Hence, the color of fluorescence changes from red to purple to blue. The ratio of the fluorescence intensities located at 612 and 438 nm varies over a wide range, with 2 linear responses ranges (from 8 nM to 12.5 µM, and from 12.5 to 75 µM). The method was applied to the determination and visual discrimination of cyanide in food and drink samples. Graphical abstract A ratiometric method for determination of cyanide detection is described that is based on mixing carbon dots (CDs) and gold nanoclusters (AuCNs). The presence of cyanide reduces the red fluorescence of the AuNCs through the formation of a stable complex Au(CN)2-. The blue emission of the CDs, in contrast, stays constant. The fluorescence intensity ratios show linear response to cyanide with a concomitant red-purple-blue fluorescence color change.

Ratiometric ultrasensitive fluorometric detection of ascorbic acid using a dually emitting CdSe@SiO2@CdTe quantum dot hybrid.

A dually emitting quantum dot nanohybrid was designed for the fluorometric 2-wavelength determination of ascorbic acid (AA). The nanohybrid consists of red-emitting CdTe quantum dots (QDs) covalently linked to the surface of silica nanoparticles containing green-emitting CdSe QDs. The fluorescence of the red-emitting CdTe QDs (peaking at 616 nm) is first quenched by addition of KMnO4 due to oxidation under formation of CdTeO3 and TeO2. On addition of AA, the red fluorescence is restored due to the reduction of surface CdTeO3/TeO2 to form CdTe. The green fluorescence of the green-emitting CdSe QDs (peaking at 522 nm), in contrast, remains constant and its intensity serves as a reference signal. Both kinds of QDs can be photoexcited at 380 nm. An easily distinguishable transition in fluorescence (from green to orange-red) can be observed on increasing the amount of added AA. Under optimal conditions, the ratio of the intensities of the red and the green fluorescence increases linearly in the 0.1 to 5.0 µM AA concentration range, and the detection limit is as low as 35 nM. The assay was successfully applied to the quantitation of AA in (spiked) fruit juice samples. Graphical abstract A new dually emitting CdSe@SiO2@CdTe nanohybrid was designed for ratiometric ultrasensitive fluorometric detection of ascorbic acid in fruit juice samples.

Semiconductor/Carbon Quantum Dot-based Hue Recognition Strategy for Point of Need Testing: A Review.

The requirement to establish novel methods for visual detection is attracting attention in many application fields of analytical chemistry, such as, healthcare, environment, agriculture, and food. The research around subjects like "point-of-need", "hue recognition", "paper-based sensor", "fluorescent sensor", etc. has been always aimed at the opportunity to manufacture convenient and fast-response devices to be used by non-specialists. It is possible to achieve economic rationality and technical simplicity for optical sensing toward target analytes through introduction of fluorescent semiconductor/carbon quantum dot (QD) and paper-based substrates. In this Review, the mechanisms of anthropic visual recognition and fluorescent visual assays, characteristics of semiconductor/carbon QDs and ratiometric fluorescence test paper, and strategies of semiconductor/carbon QD-based hue recognition are described. We cover latest progress in the development and application of point-of-need sensors for visual detection, which is based on a semiconductor/carbon quantum dot-based hue recognition strategy generated by ratiometric fluorescence technology.

[Screening of tissues pooled cDNA library using probes by restricted fragments of BAC positive clones of ovine MHC].

Under the premise what we have known bacterial artificial chromosome(BAC)clone sequence information and gene annotation predicted in the Chinese Merino sheep major histocompatibility complex (MHC) region, the digested fragments from 6 BAC clones that were located in the MHC region of the Chinese Merino sheep genome BAC library, which were used to screen the cDNA library using plaque in situ hybridization as probes. The full length of positive cDNA clones (sequences) isolated were completely sequenced, and the sequences obtained were aligned with the corresponding known sequence information and the BAC clones with gene annotation. Meanwhile, the sequence similarity was searched in NCBI Blastn database. This work aimed at verification of accuracy of the gene annotation results and initial analysis of gene (sequence) function. At last, 27 positive cDNA clones (sequences) in total were screened through two runs of hybridization. It was also found that these sequences could be positioned in the corresponding BAC clones, and 25 sequences were located in exon area of the annotated gene. It was verified that 23 sequences had the highest sequence similarity with those in the Bos taurus by searching against the NCBI Blastn database; moreover, the function of these sequences were closely relate to immunology.

Effects of Zn Contents on Microstructure and Mechanical Properties of Semisolid Rheo-Diecasting Al-xZn-2Mg-1.5Cu Alloys.

The microstructure and mechanical properties of semisolid rheo-diecasting Al-xZn-2Mg-1.5Cu alloys with different Zn contents were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), hardness testing (HV) and room temperature tensile testing. Results show that the as-cast microstructure mainly consists of spherical α-Al and Mg(Al, Cu, Zn)2 phases. Furthermore, a small amounts of Al7Cu2Fe phases were also detected along the grain boundary. Increasing the Zn contents from 8-12%, the volume fraction of the Mg(Al, Cu, Zn)2 phases increases from 4.9-7.4%. After solution heat treatment at 470 °C for 8 h, most of the Mg(Al, Cu, Zn)2 dissolves into the α-Al matrix, while the Al7Cu2Fe phase keeps with remains. The yield strength linearly increases from 482 ± 5 MPa of 8% Zn to 529 ± 5 MPa of 12% Zn. While, the ultimate strength of 10% Zn is 584 ± 2 MPa, which is higher than that of the other two alloys. Moreover, the average elongation dramatically decreases from 13% for the 8% Zn alloy to 2% for the 12% Zn alloy.

Corrosion Behavior of AISI 316L Stainless Steel Used as Inner Lining of Bimetallic Pipe in a Seawater Environment.

Seawater leakage commonly leads to corrosion in the inner lining of submarine bimetallic pipes, with significant financial implications for the offshore oil and gas production industry. This study aims to improve understanding of the performance of bimetallic pipes by investigating the corrosion behaviors of mechanically bonded 316L stainless steel. Immersion experiments were conducted in a seawater environment, under both atmospheric conditions and high temperature and high pressure conditions, and corroded surfaces were examined using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) to reveal micromorphology and elementary compositions. The results demonstrated that the corrosion rates of the bonded 316L specimen were between 5% and 20% higher than those of specimens without bonding under atmospheric conditions. This is attributed to the stress cracking that occurs during corrosion. Under high temperature and high pressure conditions, the corrosion rates were remarkably increased (91% to 135%) and the corrosion process took longer to reach equilibrium. This may be attributed, firstly, to the products becoming increasingly porous and weak, and also to the fluid stress caused by stirring in these experiments to simulate seawater movement.

A Fluorescent Metal-Organic Framework for Food Real-Time Visual Monitoring.

Due to increasing food-safety issues, exploiting efficient approaches for food quality assessment and instrumentation has attracted concerns worldwide. Herein, a smart evaluation system based on a fluorescent metal-organic framework (MOF) is developed for real-time visual monitoring of food freshness. Via post-synthetic modification, a ratiometric fluorescent MOF probe is constructed by covalently coupling fluorescein 5-isothiocyanate (5-FITC) with NH2 -rich lanthanide MOF. The probes exhibit a dual-emissive-responsive to biogenic amine, resulting in an increase in FITC emission along with a decrease in Eu3+ emission accompanied by a clear distinguishable color transition from orange red to green. After doping the probes on a flexible substrate, the obtained MOF composite film can be integrated with a smartphone-based portable platform easily. It is proved that this smart evaluation system can be used for on-site inspection of the freshness of raw fish samples. This work develops a fluorescent MOF-based smart evaluation system as a novel platform for application in food monitoring, which not only has enormous economic value but also holds great public health significance.

An europium functionalized carbon dot-based fluorescence test paper for visual and quantitative point-of-care testing of anthrax biomarker.

We reported Eu(III) functionalized carbon dots (CDs-Eu) as a novel ratiometric fluorescent probe for point-of-care testing (POCT) of dipicolinic acid (DPA), a biomarker of anthrax. The probe was synthesized simply by coordination interaction between Eu(III) ions and the CDs with carboxyl and amino groups. Upon addition of DPA, the intrinsic red luminescence of Eu(III) ions can be sensitized due to the presence of energy transfer when DPA chromophore coordinated with Eu(III) ions. The fluorescence peaking at 530 nm as a reference remained essentially constant, leading to ratiometric fluorescence response toward DPA. This approach exhibited a linearity range from 0.5 nM to 5 µM and a detection limit of 0.8 nM. More Importantly, the combination of probe-based test paper and smartphone provided a convenient approach for visual POCT of DPA with a detection limit of 67 nM, which was lower than other reported test paper for DPA detection. The color of fluorescence gradually changed from green to red as the DPA increases, which can be captured by a smartphone and further quantitatively analyzed with a built-in Color Analyzer App. The satisfactory result of detecting DPA accurately and reliably in real samples by the test paper certified its practicality in POCT of DPA.

Effect of Dietary Zinc Level on Egg Production Performance and Eggshell Quality Characteristics in Laying Duck Breeders in Furnished Cage System.

In order to investigate the effect of dietary Zn levels on laying performance, eggshell quality, and eggshell microstructure in Muscovy duck breeders under furnished cages. Firstly, the effects of age (35 weeks vs 40 weeks) and rearing system (littered floor vs furnished cage) on eggshell quality of laying duck breeders were studied (Exp. 1). Then, a total of 324 30-week-old Muscovy duck breeders were allotted into 3 dietary Zn groups with 6 replicates (18 ducks per replicate), including 0 mg Zn/kg (control-Zn group, C-Zn), 40 mg Zn/kg (normal-Zn group, N-Zn), and 140 mg Zn/kg (high-Zn group, H-Zn). The experimental period for 6 weeks was divided into 3 periods of 30-32, 32-34, and 34-36 weeks of age (Exp. 2). In Exp. 1, duck breeder eggs in the furnished cage system had lower the average shell thickness than birds in the littered floor system at 40 weeks of age (P < 0.05), not at 35 weeks of age. In Exp. 2, N-Zn and H-Zn groups had greater egg weight, egg production, and egg to feed ratio of duck breeders than C-Zn group (P < 0.05). Additionally, H-Zn group had higher laying rate, qualified egg ratio, and Haugh unit as well as lower mammillary cone width than C-Zn group (P < 0.05), with no differences between C-Zn and N-Zn groups (P > 0.05). Diet supplemented with 140 mg Zn/kg increased shell thickness and palisade layer thickness of duck breeders at 36 weeks of age (P < 0.05), but not at 32 and 34 weeks of age. In conclusion, diets with 40 or 140 mg Zn/kg improved egg production performance and egg quality of laying duck breeders during 30-36 weeks of age in a furnished cage system. Dietary supplementation of 140 mg Zn/kg level increased the ultrastructural palisade layer thickness contributing to greater eggshell thickness of duck breeders at 36 weeks of age.

Controllable and robust dual-emissive quantum dot nanohybrids as inner filter-based ratiometric probes for visualizable melamine detection.

The ratiometric fluorescence technique is of great interest due to its visualization characteristics. The construction of a reliable fluorescent ratiometric nanoprobe for high-sensitivity visual quantification is highly sought after but it is limited by poor stability and controllability. Herein, we report a robust dual-emissive quantum dot nanohybrid with precise color tunability and demonstrate its potential as a two-signal-change ratiometric probe for visual detection. A novel assembly strategy was developed for spatially implanting hydrophobic green and red quantum dots (QDs) into a silica scaffold to form a dual-emissive hierarchical fluorescent silica nanohybrid. The fluorescence intensity ratio and color of the nanohybrid were precisely tailored by altering the amounts of green and red QDs. Particularly, after the alkylsilane-mediated phase transfer and exterior silica shell growth, the nanohybrid exhibited the well-preserved fluorescence features of the original QDs and robust optical/colloid stability. An inner filter-based ratiometric nanoprobe for the visual determination of melamine was ultimately devised by combining the spectra-overlapped two-colored fluorescent nanohybrid with analyte-specific gold nanoparticles. Furthermore, based on the reversible fluorescence signal changes in two-colored QDs induced by melamine, a logic gate strategy for melamine monitoring was constructed. The newly developed fluorescent ratiometric nanoprobe shows great prospects for the visual and quantitative determination of analytes in a complex biological matrix.

[Expression of OPN gene during different lactation stages in mammary gland of dairy goat and its effect on growth of MCF-7 cell line].

To investigate the expression pattern and preliminary function of OPN gene in mammary gland of dairy goat during different lactation stages, using b-actin gene as the internal control, the SYBR Green quantitative real-time PCR (QPCR) analysis was conducted to determine the mRNA expression of OPN gene in mammary gland at the 28th, 60th, 100th, 190th, 270th and 330th day after kidding. Recombinant plasmid of pcDNA3.1-OPN was constructed by inserting the fragment of OPN gene into eukaryotic expression vector pcDNA3.1 and used to transfect the MCF-7 cell line following the restrictive endonuclease cleavage and sequence identification of the target gene segment, the effect of OPN gene on MCF-7 cell proliferation was assessed by MTT analysis. The results indicated that OPN gene exhibited the higher expression level in early (28 d) and late (190 d) lactation stages and the lowest level at dry stage (330 d), which demonstrated a high-low-high-low pattern. There was a significant difference (P < 0. 05) in the proliferation between OPN gene transfected and non-transfected MCF-7 cells, which suggested that the expression of OPN gene could stimulate the proliferation of MCF-7 cells.

Mold-Slug Interfacial Heat Transfer Characteristics of Different Coating Thicknesses: Effects on Slug Temperature and Microstructure in Swirled Enthalpy Equilibration Device Process.

Application of a coating on a mold surface is widely used in the foundry industry. Changes in coating change the heat transfer at the mold-melt interface, which influences the microstructure of the casting. In this study, the effect of boron nitride coating thickness on the interfacial heat transfer and slug microstructure in the Swirled Enthalpy Equilibration Device (SEED) process was investigated. The temperatures of the semi-solid slug and mold were measured, and the interfacial heat transfer coefficient and heat flux of the mold-slug interface was estimated based on these data. Microstructures of the quenched slugs were also examined. The results indicated that the interfacial heat transfer coefficient decreased with an increase in coating thickness and was sensitive to a coating thickness of less than 0.1 mm. The interfacial heat flux decreased sharply at the early stage, and then slowed down as the swirling time increased and the coating thickened. The coating thickness affected the temperature evolution of the slug at the early stage of the SEED process. As the coating thickness increased from near zero to 1.0 mm, the grain size of the slug increased by ~20 µm and the globular structure of the slug transformed into a dendritic structure.

Effect of Temperature Gradient on the Grain Size Homogeneity of SEED Produced Semi-Solid Slurries by Phase-Field Simulation.

The distribution homogeneity of grain size affects the fluidity of the semi-solid slurry, which in turn affects the properties of the casting. One key factor affecting grain size uniformity resides in the nucleation number, which has been studied thoroughly, while the other factor is temperature gradient which has not been investigated yet. In this study, the microstructure evolutions under certain temperature gradients are investigated by experiment and simulation using a two-dimensional quantitative phase-field (PF) model. A parallel and adaptive mesh refinement algorithm is adopted to solve the nonlinear phase-field equations. The results indicate that temperature gradient can affect the size distribution of microstructure in the semi-solid slurry prepared by the SEED process. A higher temperature gradient (in the range of 0.230~0.657 °C/mm) along the radial direction is beneficial to the homogeneity of the grain size in a slurry.

[Expression of ER, bcl-2, and p53 mRNA in early hybrid embryos of chicken-quail].

Using artificial insemination, 100 female quails were crossed with 10 male chickens. The eggs were collected and hatched in the same incubator. The sex of live hybrid embryos from 66 to 120 hatch hours was determined using multiply PCR of Wpkci. Total 300 male and female embryos at various hatch times were sampled and the relative mRNA abundance of ER, bcl-2, and p53 in the embryos was detected by RT-PCR using beta-actin as the internal standard. The effects of ER, bcl-2, and p53 on the early embryonic development for hybrids between chicken and quail were analyzed. The results showed ER mRNA expression of female hybrids were higher than male hybrids from 66 to 84 hatch hours with a highly significant difference (P<0.01), which indicated that the sex differentiation of hybrids was perhaps happened between 66 to 84 h of embryo stage. The obvious sequential expression of bcl-2 and p53 in the embryonic development indicated that the bcl-2 and p53 genes had an important effect on the development of the hybrid embryos.

[Polymorphism distributions of 9 microsatellite Loci in Chinese merino sheep].

The polymorphism distributions of nine microsatellite loci, BM6506, BM1824, BM6438, ILSTS004 and OarDB6 on Chinese merino sheep chromosome 1 and BM4621, OarHH55, BM143 and OarJMP8 in sheep chromosome 6 were determined by polymerase chain reaction (PCR) and multiplex gel electrophoresis followed by silver staining. Gene frequency (Pi), power of discrimination (DP), heterozygosity (H), polymorphism information content (PIC) and probability of paternity exclusion (PE) were calculated. All loci obeyed Hardy-Weinberg equilibrium. BM4621 displayed the highest DP, H, PIC and PE values among the nine microsatellite loci. Cumulative DP of the nine microsatellite loci is 0.99999 and cumulative PE is 0.99915. These results showed that the nine microsatellite loci could be used in linkage analysis, individual identification and paternity test in Chinese merino sheep.