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The blood-brain barrier (BBB) is a highly selective semi-permeable barrier that separates circulating blood from the extracellular fluid of the brain and central nervous system, which is crucial for maintaining brain homeostasis. This study aimed to explore the role of propofol in BBB damage and further evaluate the underlying molecular mechanism. Lipopolysaccharide (LPS) was administered to mice to create an in vivo BBB damage mice model. Additionally, hCMEC/D3 cells as brain microvascular endothelial cells (BMECs) were treated with LPS to establish the in vitro BBB damage cell model. Subsequently, propofol was used for the BBB damage model. Evans blue staining and fluorescein sodium were utilized in the in vivo experiments to demonstrate BBB leakage and BBB permeability. Cell counting kit-8 (CCK-8) assay was used to assess cell viability and the trans-endothelial electrical resistance (TEER) value was measured using an epithelial voltmeter. Furthermore, enzyme-linked immunosorbent assay was performed to measure the levels of the inflammatory cytokines such as interleukin-1β (IL-1β) and tumor necrosis factor-alpha (TNF-α). The levels of miR-130a-5p and zonula occludens-1 (ZO-1) in brain tissues and cells were detected using reverse transcription-quantitative polymerase chain reaction, western blot, or immunofluorescence staining. Furthermore, a dual-luciferase reporter assay was used to demonstrate the association between miR-130a-5p and ZO-1. Propofol treatment suppressed BBB leakage, the amount of fluorescein sodium, and the levels of IL-1β and TNF-α in the LPS-induced BBB damage mice model. Meanwhile, propofol treatment increased the TEER value in the LPS-induced hCMEC/D3 cells. Additionally, propofol treatment significantly down-regulated miR-130a-5p and up-regulated ZO-1. More importantly, miR-130a-5p directly targeted ZO-1 and negatively regulated ZO-1 expression in hCMEC/D3 cells. Furthermore, miR-130a-5p mimic partially reversed the effect of propofol on the TEER value and the levels of inflammatory cytokines such as IL-1β and TNF-α in the LPS-induced hCMEC/D3 cells. Propofol suppressed LPS-induced BBB damage by regulating miR-130a-5p/ZO-1 axis. These findings suggested a potentially effective treatment approach for BBB damage. [ABSTRACT FROM AUTHOR]

The primary focus of traditional topological optimization in continuum structures is addressing stress, compliance, and other relevant factors associated with single-phase materials. However, the optimal design of structural buckling performance has gained increasing attention due to its significant economic loss and safety risk. Furthermore, the versatility, lightweight nature, and adjustability of composite multiple-phase materials offer significant potential for application in various fields. Therefore, this paper presents a novel methodology for optimizing multi-phase materials' design by concurrently incorporating structural buckling criteria and compliance design. Linear buckling analysis is utilized to determine the critical buckling load of the structure, and a buckling constraint is incorporated into the topology optimization model to regulate its buckling performance. A refined material interpolation model scheme is introduced to enhance the algorithm's robustness and eliminate pseudo-eigenmode in buckling analysis. The numerical results demonstrate that the final topology optimization design exhibits distinct and discernible boundaries for the topological configurations of multiple-phase materials. Moreover, it is possible to effectively regulate the buckling property while minimizing any compromise on stiffness. [ABSTRACT FROM AUTHOR]

Owing to the difficult degradation of phenolic compounds, the existence of phenolic compound residues accumulated through the food chain in crustaceans and their effects on human health have garnered considerable and more attention. However, the current detection methods for phenolic compounds are not only complex and time-consuming but can also detect fewer types of phenols simultaneously. Thus, a simple, high-throughput method without derivatization for the determination of 18 phenolic compounds in crustaceans was developed using a modified QuEChERS sample preparation method combined with gas chromatography-mass spectrometry. The results indicated that the average recovery of the 18 phenolic compounds was 80.2–106.5% at three spiked levels, and the relative standard deviation was 2.6–12.4%. The limits of detection and quantitation were 0.001–0.014 and 0.003–0.042 mg/kg, respectively. Good linear relationships were observed for the phenolic compounds in their corresponding concentration ranges (R2 > 0.999). The applicability of the method was assessed by analyzing 16 actual shrimp samples, among which five samples contained residues ranging from 0.013 to 0.042 mg/kg. Moreover, the establishment of this method has important theoretical and practical significance for the determination and control of the residue levels of phenolic compounds in crustaceans. In addition, it can provide a reference for the development of similar detection standard methods in the future. [ABSTRACT FROM AUTHOR]

With the tremendous development of additive manufacturing technology in recent years, porous infill structures with well-designed topology configurations have been widely used in various physical fields. The porous infill structure may be prone to thermo-mechanical buckling failure under certain extreme thermal conditions due to temperature gradient effects and delicate local details of the porous infill structure.Therefore, a topological optimization design method, which considers the influence of the thermo-solid coupling field on the buckling performance of the porous infill structure, is proposed by using the projection approach merged with the Solid Isotropic Material with Penalization (SIMP) method. Critical buckling load factors obtained with thermal-elastic equilibrium and linear buckling analysis are employed to measure the buckling performance of the structure. Numerical examples show that the proposed method can effectively improve the buckling performance of the porous infill structure under the thermo-mechanical environment. [ABSTRACT FROM AUTHOR]

A dual-mode aptasensor using colorimetry and microfluidic chip (MC) together with stir bar sorptive extraction (SBSE) has been developed for firstly qualifying samples contaminated with Vibrio parahaemolyticus (V.P) and Salmonella typhimurium (S.T), then precisely determine both of them in positive samples. For this purpose, the aptamer-streptavidin encoded probes (Apt-SAEs) corresponding to different bacteria were prepared in advance. Then, a stir bar modified with 4-mercaptophenylboronic acid (MPBA) was made to extract bacteria together with Apt-SAE probes. The binding event of aptamer and target triggered the formation of two sandwich structures containing Apt-SAE, V.P or S.T. The concentration of bacteria could be enriched by 1000 times within 15 min to avoid long-time enrichment process. Finally, the stir bar was immersed in the 3,3′,5,5′-Tetramethylbenzidine (TMB)-H2O2 solution for color development. The color could be observed by naked eyes to judge whether the analytes were present. The colorless samples were judged to be negative. For the positive samples, the adsorbed encoded probes corresponding to different bacteria would be eluted from the stir bar and rapidly analyzed by the MC. Under the optimized conditions, 100 CFU/mL of V.P or S.T or both of them could be observed by colorimetry and 35 CFU/mL of them could be detected (S/N = 3) by the MC. The assay has significant application value for on-site screening and multiple detection of food-borne pathogenic bacteria. [ABSTRACT FROM AUTHOR]

A pair of composite probes based on aptamer modified polyhedral oligomeric silsesquioxane-perovskite quantum dots (POSS-PQDs-Apt) as signal probe and titanium carbide (Ti3C2) MXenes as quencher were prepared for the first time. They were employed to fabricate one turn-on–type aptasensor relying on fluorescence resonance energy transfer (FRET) for Vibrio parahaemolyticus (VP) determination. The POSS-PQDs-Apt can be adsorbed on the MXenes nanosheets, and its fluorescence was quenched due to the FRET. After the composite probes were incubated with VP for 50 min, the POSS-PQDs-Apt binding with VP can be released from the surface of MXenes, and the signal recovered due to its higher affinity to the VP than MXenes. The fluorescence intensity from 519 nm emission of the system was measured at 480 nm excitation. Under In optimized conditions, the assay can determine VP in the concentration range 102 - 106 cfu/mL, and the detection limit (LOD) was 30 cfu/mL using fluorescence detection. The LOD is still 100 cfu/mL by naked eye detection which is proper for on-line monitoring VP in aquaculture water. This method was also used to detect VP in actual samples of seawater, the recovery of spiked samples was between 93% and 106%, and relative standard deviation (RSD) was between 2.7% and 6.7%. The result is consistent with the plate count. Therefore, this assay could provide a candidate platform for screening VP in aquaculture industry. [ABSTRACT FROM AUTHOR]

Let X be a Hopf manifold with non-Abelian fundamental group and E be a holomorphic vector bundle over X, with trivial pull-back to ℂn − {0}. The authors show that there exists a line bundle L over X such that E ⊗ L has a nowhere vanishing section. It is proved that in case dim(X) ≥ 3, π*(E) is trivial if and only if E is filtrable by vector bundles. With the structure theorem, the authors get the cohomology dimension of holomorphic bundle E over X with trivial pull-back and the vanishing of Chern class of E. [ABSTRACT FROM AUTHOR]

The authors describe a microfluidic chip-based aptasensor platform combined with magnetic tripartite DNA structure-functionalized nanocomposites to achieve simultaneous determination of kanamycin (KANA), aflatoxin M1 (AFM1), and 17β-estradiol (E2) in milk. The two-duplex tripartite DNA nanostructure was first assembled on the surface of magnetic beads. When the aptamer on the probes recognized the specific target, the aptamer-target would be released into the supernatant. The pre-primer@circular DNA template structure initiates rolling circle amplification (RCA) by phi29 polymerase. After magnetic separation, the magnetic nanocomposites were added into a solution containing three different lengths of complementary strands to the RCA products. The number of complementary strands significantly decrease, and this can be quantitated by the microfluidic chip. Further, the employment of magnetic nanocomposites and microfluidic chip not only resolve the complex matrix interference, but also dramatically enhances the determination selectivity and sensitivity. This aptasensor allows for determination of KANA, AFM1, and E2 with limits of detection as low as 0.32 pg mL−1, 0.95 pg mL−1, and 6.8 pg mL−1, respectively. This novel method exhibits the advantages of excellent stability and fast response time (< 3 min on microfluidic chip platform) for simultaneous determination of KANA, AFM1, and E2 in milk samples and ensures food safety. [ABSTRACT FROM AUTHOR]

Accurate data of flammability limits for flammable gases and vapors are needed to prevent fires and explosions. The flammability limit, which is the maximum or minimum fuel concentration at which a gas mixture is flammable in a given atmosphere, has been studied for decades. However, due to differences in measurement conditions and equipment used, the flammability values exhibit significant variations, especially at elevated temperature and pressure. In this study, the flammability limits of methane-air were measured in a closed cylindrical vessel with upward flame propagation at a maximum initial temperature of 300 °C and a maximum initial pressure of 2 atm. The combustion behavior and flame propagation properties are compared using different flammability criteria. Test results have shown that 7% pressure criterion is a conservative standard that can be applied for nonstandard vessel flammability test. Also, experimentally measured values are compared with existing data in the literature to study the influence of temperature, pressure and apparatus. In consideration of safe usage and storage, for each flammable gas substance at elevated condition, experimentally determined values should be used rather than extrapolated ones using estimation correlations. [ABSTRACT FROM AUTHOR]

The authors describe an ultrasonic-assisted headspace method for solid phase micro-extraction (UA-HS-SPME) of 7 polychlorinated biphenyls (PCBs) with codes PCB28, PCB52, PCB101, PCB118, PCB138, PCB153 and PCB180. The coating is based on a poly-dopamine metal-organic framework [PDA-MIL-53(Fe)] on a stainless steel wire. The coating can be prepared and evenly deposited on the stainless fiber by dipping the PDA fiber into a solution of MIL-53(Fe). The assay is also environmentally friendly because water is used as the solvent. The effects of extraction time, addition of salts, pH value and power of ultrasonic power were optimized. The coating is found to possess a high selectivity and adsorption capacity for PCBs compared to commercial SPME fibers such as the divinylbenzene/carboxen/polydimethylsiloxane fibers. Following desorption, the PCBs were quantified by GC-MS. The detection limits are between 50 and 90 pg⋅g of PCBs in soil. The fibers can be easily prepared, and the batch-to-batch reproducibility (RDS) is <10% (for n = 6). The fibers are inexpensive, re-usable and can be easily manipulated, and particularly well suited for screening polychlorinated biphenyls in soil. [ABSTRACT FROM AUTHOR]

This study aimed to simultaneously determine three β2-agonists (clenbuterol, salbutamol, and ractopamine) in pork samples using novel stir bar array sorptive extraction coupled with gas chromatography-mass spectrometry. Pencil refill was employed as the substrate of stir, which was covered with carboxyl graphene sheets and polyluminol coating. The coating was simply prepared by electrochemical deposition of luminol at a voltage of 0-0.6 V. Then, an automatic device with the stir bar array for extraction was used. The conditions for the extraction were optimized. Under the optimum extraction conditions, with toluene as the extraction solvent, the extraction and desorption times were 20 min. A good linearity of three β2-agonists was obtained in the range of 0.5-100 ng g by gas chromatography-mass spectrometry detection. The recovery of clenbuterol, salbutamol, and ractopamine in spiked pork samples ranged from 88.7 to 93.2%, 85.5-94.2%, and 85.7-93.9%, respectively, with the relative standard deviations less than 10%. The detection limits were in the range of 0.022-0.091 ng g for pork samples. The extraction coating with high extraction capacity was simply fabricated by the electrochemical method, which could simplify the pretreatment procedures. Moreover, the array could extract several samples simultaneously and improve the pretreatment efficiency. Graphical Abstract: [ABSTRACT FROM AUTHOR]

The article describes a multiplex aptamer based voltammetric assay for the food pollutants chloramphenicol (CAP) and polychlorinated biphenyl-72 (PCB72). The method is based on the displacement of a nanotracer (an aptamer-labeled magnetic dendritic probe) by the analytes which cause the release of the corresponding encoded nanotracers. Thiolated aptamers of CAP and PCB72 were first self-assembled on magnetic gold nanoparticles (FeO@Au) as capture probes to concentrate the target analytes CAP and PCB72, respectively. Next, their hybridized complementary strands (cDNA1 or cDNA2) and a dendritic polymerase were linked to quantum dots (CdS or PbS) to form the respective nanotracers. Finally, encoded composite magnetic probes were obtained through hybridization reaction between aptamers and cDNAs. Once CAP and PCB72 are recognized by the composite probes, the nanotracers are released into the supernatant where they can be detected simultaneously by voltammetry of the metal ion markers Cd(II) and Pb(II) at −0.81 and −0.57 V (vs. Ag/AgCl), respectively. The concentration measured for Cd(II) and Pb(II) are directly proportional to the concentrations of CAP and PCB72, respectively, in the range from 0.001 to 100 ng mL. The detection limits for CAP and PCB72 are 0.33 and 0.35 pg mL, respectively (at an S/N ratio of 3), which is 2 to 3 orders of magnitude lower than the routinely performed and commercially available ELISA. The method is perceived to possess large potential in that it may be applied to other antibiotics by using the appropriate aptamers. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

We describe an aptamer-based colorimetric assay for chloramphenicol (CAP) based on the ability of anti-single-stranded DNA antibody (anti-ssDNA Ab) to recognize ssDNA, and the catalytic ability of PowerVision (PV), which is a polymeric conjugate of horseradish peroxidase and antibody with a high enzyme-to-antibody ratio. The complementary DNA of the aptamer (cDNA) was immobilized on magnetic gold nanoparticles (FeO@Au) and used as a capture probe (AuMNPs-cDNA). The ssDNA Ab and PV were conjugated to AuNPs to form signal tags that recognize ssDNA with anti-ssDNA Ab to form beads containing the amplified probe (AuMNPs-cDNA@anti-ssDNA Ab/PV-AuNPs). The PV on their surface catalyzes the oxidation of the substrate 3,3',5,5'-tetramethylbenzidine to produce a color change which is quantified by absorptiometry at 652 nm. The assay has a linear calibration plot for CAP in the 0.01 to 100 ng mL range, with a detection limit as low as 3 pg mL. The method was successfully employed to detect CAP in real samples. Results were consistent with data obtained using a conventional enzyme-linked immunosorbent assay. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

A portable and antibody-free sandwich assay was fabricated for determination of chloramphenicol (CAP) in animal-derived food by a personal glucose meter (PGM). The sandwich-type strategy was developed on the basis of magnetic molecularly imprinted probe (m-MIP) nanoparticles and a β-cyclodextrin/invertase-functionalized signal tag. Firstly, the m-MIPs were fabricated using polydopamine molecularly imprinted film modified FeO nanoparticles with 2,2-dichloroacetamide as a template that could capture the 2,2-dichloroacetamide segment of CAP. Secondly, β-cyclodextrin/invertase polymer bioconjungate was synthesized as a signal tag that could recognize the nitrobenzene segment of CAP through host-guest interaction. The dual-specificity recognition model relies on the formation of a sandwich between m-MIPs, different segments of CAP, and the β-cyclodextrin-functionalized signal tag. The sandwich-type complex formed was then subjected to detection with a PGM. The complexes can hydrolyze sucrose to glucose, which can be used for detection with a PGM through invertase. According to our experiment, the concentration of CAP was proportional to the amount of glucose formed, which could quantitatively assess the CAP with a dynamic range of 0.5-50 ng mL and a detection limit of 0.16 ng mL (signal-to-noise ratio of 3). The detection time of the assay was about 1 h, which was obviously shorter than that of competitive ELISA. More importantly, we have successfully applied this on-site assay for CAP screening in animal-derived food. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

We report on an on-site ultrasensitive sandwich immunoassay for ractopamine (RAC) that is based on the use of a personal glucose meter. RAC is preconcentrated with the help of magnetic nanoparticles coated with β-cyclodextrin (FeO@SiO-CD), and a novel polymer tag labeled with invertase is employed to catalyze the hydrolysis of sucrose to form glucose which is detected with the glucose meter. Invertase-modified gold nanoparticles were prepared and immobilized, along with antibodies against RAC, on an Envision reagent (a polymer that contains many anti-IgG antibodies). Because of its high loading with the enzyme, the resulting copolymers strongly amplify the signal. The concentration of RAC is calculated on the basis of the linear relationship between the concentration of RAC and the amount of glucose formed. The method exhibits a detection limit of 0.34 μg kg as determined for a sample of pork. This on-site testing method may also be applied to the detection of other low-molecular toxins by simply changing the antibody. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

We report on the preparation of magnetic nanoparticles coated with a surface imprinted polymer for use in the preconcentration of diethylstilbestrol (DES). The magnetic molecularly imprinted nanoparticles (m-MINPs) were fabricated by first coating magnetite nanoparticles with a layer of Nafion which is polyanionic. Next, the resulting particles were coated with polydopamine (which is polycationic at near-neutral pH values) in the presence of DES as a template. The thickness of the coating containing the DES template is quite thin so that it can be removed within 18 h. The m-MINPs devoid of DES have a typical diameter of 500 nm and exhibit fast adsorption kinetics and sensitive magnetic response to a magnet. The m-MINPs can recognize DES with high specificity over many other estrogens (separation factor β >1.9) and were employed for the dispersive solid-phase extraction of DES which then was quantified by HPLC. The method was applied to determine DES in (spiked) milk powder samples. The recoveries ranged from 90.7 to 105.2 % (intra-day) and from 85.5 to 102.3 % (inter-day) at spiking levels of 10, 50, and 100 ng g. The linear ranges were 3.5-1,000 ng g with the correlation coefficient of 0.9983. The detection limit was 0.99 ng g of milk powder. The m-MINPs are reusable. After 12 adsorption-elution cycles, the recovery was still higher than 80 %. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

We report on a novel enzyme-enhanced label for the electrochemical determination of diethylstilbestrol (DES). The label was obtained by orientation-controlled immobilization of a multiplex horseradisch peroxidase (HRP) conjugated polymer on gold nanoparticles (AuNPs) using the Envision reagent (EV) which is an enzyme-polymer complex that contains HRP and anti-IgG antibody in a polydextrin amine skeleton. The AuNPs were modified with Concanavalin A (Con A) and served as a carrier for immobilization of the EV−DES antibody composite. This resulted in a bioconjugate of the type AuNP−Con A−EV−DES Ab which was employed as the label. On exposure to samples containing DES, a sandwich immunocomplex is formed between antibody against DES (which was immobilized on a glassy carbon electrode and is acting as a capture probe), DES (the analyte), and the above label as the signal tracer. Hemin was used as an electronic mediator in the reaction of HRP. The HRP on the label catalyzes the oxidative formation of hydrogen peroxide at pH 7.0, and this induces an increased reductive current in the presence of hemin as an electron mediator. Under optimal conditions, the current increases linearly with increasing concentrations of DES in the range from 5 to 500 pg · mL, with a detection limit as low as 2 pg · mL (at an S/N of 3). The method exhibits high selectivity and good stability. It works without incubation so that the time for an assay is shortened to 5 min. The assays was successfully applied to the determination of DES in milk samples. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

We have prepared core-shell magnetic molecularly imprinted polymer nanoparticles for recognition and extraction of tributyl tin (TBT). The use of particles strongly improves the imprinting effect and leads to fast adsorption kinetics and high adsorption capacities. The functional monomer acrylamide was grafted to the surface of FeO nanospheres in two steps, and MIP layers were then formed on the surface by creating a MIP layer on the surface consisting of poly(ethyleneglycol dimethacrylate) with a TBT template. The particles were characterized in terms of morphological, magnetic, adsorption, and recognition properties. We then have developed a method for the extraction of TBT from spiked mussel (Mytilidae), and its determination by liquid chromatography-tandem mass spectrometry. The method has a limit of detection of 1.0 ng g ( n = 5) of TBT, with a linear response between 5.0 and 1,000 ng g. The proposed method was successfully applied to the determination of trace TBT in marine food samples with recoveries in the range of 78.3-95.6 %.[Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

An aptamer based assay is presented that is making use of a catalytic hybrid assembly and a microfluidic chip electrophoresis format. It enables simultaneous determination of the biomarkers (BMs) α-fetoprotein (AFP), carbohydrate antigen 125 (CA125), and carcinoembryonic antigen (CEA). The respective aptamers were covalently bound to Fe3O4@AuNPs (AuMPs) magnetic beads and then used to capture the biomarkers on their surface. Different single-stranded DNA primers were then labeled with various antibodies as encoding and signaling tags. The signal tags reacted with AuMPs-BMs to form different antibody-BM-aptamer complexes. After magnetic separation, three pairs of hairpins as substrates were introduced to trigger catalytic hybrid assembly by the primers in the complex. This will form many duplex DNA products of different length in the supernatant. The products can be magnetically separated by microfluidic chip electrophoresis and determined by fluorometry at excitation/emission wavelengths of 495/525 nm. Several experimental conditions including the hairpin concentration, reaction time and temperature were systemically optimized. The method can simultaneously quantify AFP, CEA and CA125, respectively, with detection limits of 0.1, 0.2, 0.15 pg mL−1 (at S/N = 3). The aptamer functionalized magnetic beads can be reused for at least 20 times with a recovery of up to 80% after heat treatment. The method was employed to simultaneously detect the three BMs in serum samples. [ABSTRACT FROM AUTHOR]

An enzyme-free fluorometric assay is described that accomplishes dual signal amplification by making use of a two stirring bars. Two Y-shaped DNA probes were designed and placed on the bars. When the target (with chloramphenicol as model analyte) is added, it triggers target recycling and simultaneously catalyzes hairpin assembly (CHA). A large fraction of DNA primers is released by the analyte from the bar to the supernatant and open hairpins with G-quadruplex DNA sequence. The G-quadruplex can specifically bind thioflavin T (ThT) to emit fluorescence (with excitation/emission maxima at 445 and 485 nm) for quantification of chloramphenicol. An enzyme is not needed. ThT is added to the system as a fluorescent DNA probe. All this strongly reduces the cost for sensor construction and usage. The dual signal amplification steps occur simultaneously which reduces the detection time. The assay was successfully employed to the determination of CAP in spiked milk and fish samples within 60 min and with a 16 pM limit of detection (at S/N = 3).Schematic representation of a new method for the detection of chloramphenicol by using  two stirring bars. It is based on target recycling and catalyzed hairpin assembly amplification. CAP: chloramphenicol, ThT: thioflavin T, CHA: catalyzed hairpin assembly. [ABSTRACT FROM AUTHOR]

A simple and highly sensitive fluorometric method is described for the determination of the antibiotic kanamycin (Kana) in food. Dual signal amplification is accomplished by making use of double Y-shaped aptamer DNA probes acting as a capture probes and signal amplification probes. The DNA probes were immobilized on a gold bar and on a magnetic bar, respectively. On addition of Kana, the Y-shaped aptamer probe captures Kana and then is disassembled to release two single-stranded DNAs. These trigger target recycling and HCR between the two bars simultaneously. As a result, many long duplex DNA chains are formed in the supernatant. After pulling out the bars and adding the fluorescent intercalating probe SYBR Green I, strong fluorescence (with excitation/emission peaks at 497/525 nm) is induced. The use of such double Y-shaped DNA probes obviously overcomes the unspecific signal amplification by HCR which increases selectivity and sensitivity. This is due to the fact that the hairpin of HCR is separated in being present in different arms of the Y-shaped probe. Under the optimal conditions, the assay has a limit of 0.45 pg·mL−1 for Kana. It was applied to analyze spiked milk, fish and pork samples.The scheme represents a sensitive fluorometric aptamer-based method to detect kanamycin (Kana). It is making use of a double stirring bar-assisted dual amplification strategy with zero background. Abbreviations: apt: aptamer, AuNPs: gold nanoparticles, HCR: hybridization chain reaction. [ABSTRACT FROM AUTHOR]