Zobrazení zdroje stránky Johanssonpatterson1075

Upon the addition of Hg2+, the aptamer was bent due to the formation of thymine-Hg2+-thymine (T-Hg2+-T) specific structure, which caused the self-enhanced ECL composite was close to the GCE surface. On this basis, a linearly enhanced ECL signal was acquired with the concentration of Hg2+ in the range of 5.0 × 10-11 M - 1.0 × 10-6 M with excellent selectivity, repeatability and stability in 3 min for each assay. In addition, the proposed aptasensor showed satisfying accuracy and practicability for Hg2+ analysis in tap and canal water verified by the inductively coupled plasma-mass spectrometry (ICP-MS) method.This work reports the development of an electrical and optical biosensing for label-free detection of Aflatoxin B1 (AFB1) using gold (Au) nanobipyramids (NBPs). AuNBPs were synthesized through a two-step seed-mediated growth process followed by an exchange of capping agent from surfactant to lipoic acid. Pure and monodispersed AuNBPs of 70 nm base length were obtained and deposited on indium tin oxide (ITO)-coated glass substrate modified with self-assembled (3-Aminopropyl) triethoxysilane (APTES) film. The characterization of the obtained surfaces using spectroscopy, microscopy and diffractometry confirms the formation of AuNBPs, the conjugation to ITO electrode substrate and the immobilization of anti-AFB1 antibodies. AuNBPs modified ITO substrates were used for both electrochemical and Surface Plasmon Resonance biosensing studies. Localized Surface Plasmon Resonance (LSPR) local field enhancement was demonstrated. SPR based AFB1 detection was found to be linear in the 0.1-500 nM range with a limit of detection of 0.4 nM, whereas, impedimetric AFB1 detection was shown to be linear in the 0.1-25 nM range with a limit of detection of 0.1 nM. The practical utility of the impedimetric sensor was tested in spiked maize samples and 95-100% recovery percentage was found together with low relative standard deviation, proof of the robustness of this AFB1 sensor.Salmonella is a principal causal agent of pathogenic outbreaks via food. A universal, highly sensitive and visual Salmonella detection method was proposed in this paper, based on a universal linker PCR (UL-PCR)-triggered Strand Displacement Amplification (SDA). In this research, the UL-PCR achieved the primary amplification. The universal linker primer was ingeniously designed and composed of two parts, one of which was the binding sequence of the target, and the other was the universal linker. Complementary sequences of the G-quadruplex and the nicking endonuclease recognition sequence were included in the universal linker. Therefore, the G-quadruplexes and nicking sites were successfully introduced into the UL-PCR products, providing a basis for further SDA triggering. SDA achieved the secondary signal amplification and generated a large amount of label-free DNAzymes. Following SDA, DNAzymes catalyzed 3,3',5,5'-tetramethylaniline (TMB) into colored compounds visible to the naked eye. We obtained the best experimental conditions by univariate analysis. Under optimal conditions, this proposed universal label-free method could detect Salmonella genome at level as low as 22 copies mL-1, with an excellent linear range between 102 copies mL-1 and 107 copies mL-1. And the limit of quantification (LOQ) was 102 copies mL-1. This strategy shows promise for broad applications.The increased attraction of biological volatile compounds has opened the route to a wide variety of sampling techniques, amongst which trap tubes packed with adsorbent materials are commonly used. Many types of adsorbent materials are available and the choice of the adsorbent can impact the obtained results in untargeted analysis. Therefore, a proper combination of the adsorbent material and the sample is necessary to increase the robustness and reproducibility of biological studies. In this study, the sampling performance of thermal desorption tubes with six common adsorbent material combinations, i.e., Tenax® TA, Tenax® TA/Carbopack™ B, Tenax® TA/Sulficarb, Tenax® TA/Carbograph™ 5TD, Tenax® TA/Carbograph™ 1TD/Carboxen® 1003, and Carboxen® 1016/Carbograph™ 5TD, was evaluated in two different setups in vitro and in vivo sampling. The in vitro setup consisted of the headspace dynamic extraction of spiked serum, and a mixture of 19 standards was evaluated in terms of response and reproducibility. The in vivo setup consisted into two parts the first one was based the evaluation of the standard mixture, which was flash-vaporised into Tedlar® bags containing exhaled breath; the second part was based on the longitudinal monitoring of breath metabolites originating from a beverage intake (i.e., brewed coffee), over a 90 min time period. The tubes were all desorbed and analysed in a comprehensive two-dimensional gas chromatography system coupled to a high-resolution time-of-flight mass spectrometer (GC × GC-HR ToF MS). In both sampling setups, the widest analytes coverage and the overall best extraction yield on the selected compounds were obtained using Tenax® TA, followed by Tenax® TA/Carbopack™ B. Tenax® TA provided the highest sampling reproducibility with 12 %RSD, 10 %RSD and less then 5 %RSD of the response during the experiments using the in vitro setup, the in vivo setup, and during the longitudinal tracking, respectively.Superoxide anion (O2•-) is an important biomarker for reactive oxygen species (ROS) generated through physiological and pathological processes. However, due to the short half-life of O2•- and high autofluorescence of cell tissues, in situ real-time tracking and monitoring of endogenous O2•- can be difficult. In this paper, a fluorescent probe IFP-O2 was developed to detect endogenous O2•- in cells. [https://www.selleckchem.com/products/cc-92480.html this website] The probe could instantaneously react with O2•- to produce fluorescence off-on effect; its detection limit was as low as 10 nM. Cell experiments also showed that the probe had low toxicity and mitochondrial targeting ability. The article presents, for the first time, a probe that can be employed to measure endogenous O2•- in oral cancer Cal-27 cells and is a promising tool for monitoring and evaluating apoptosis.It has seen increasing development of reliable, robust, and flexible biosensors for rapid food-safety analysis in the past few decades. Recently, functional nucleic acid-based biosensors have attracted attention because of their programmability, bottom-up characteristics, and structural switches. However, few systematic reviews devoted to categorizing the potential of DNA nanostructures and devices were found for detecting food contaminants. Hence, the applications of functional nucleic acid-based biosensors were reviewed for analyzing food contaminants, including foodborne pathogen bacteria, biotoxins, heavy metals, and et al. In addition to categorizing the various biosensors, multiple signal readout strategies, such as optical, electrochemical, and mass-based signals were also examined. Finally, the future changes and potential opportunities, as well as practical applications of functional nucleic acid-based biosensors were discussed.This paper proposes a ROC curve-based methodology to find optimal classification model parameters. ROC curves are implemented to set the optimal number of PCs to build a one-class SIMCA model and to set the threshold class value that optimizes both the sensitivity and specificity of the model. The authentication of the geographical origin of extra-virgin olive oils of Arbequina botanical variety is presented. The model was developed for samples from Les Garrigues, target class, Samples from Siurana were used as the non-target class. Samples were measured by FT-Raman with no pretreatment. PCA was used as exploratory technique. Spectra underwent pre-treatment and variables were selected based on their VIP score values. ROC curve and others already known criteria were applied to set the threshold class value. The results were better when the ROC curve was used, obtaining performance values higher than 82%, 75% and 77% for sensitivity, specificity and efficiency, respectively.This study substantially synthesized the β-type MnO2 nano-flowers assembled by the hierarchical nano-sheets using a simplified hydro-thermal procedure. According to the FESEM images, MnO2 nano-flower exhibited diameter of ∼800 nm and fabricated with a lot of irregular sheets as a petal-like structure with thickness of several nano-meters. Therefore, the study focused on the construction of an electro-chemical sensor to simultaneously determine theobromine (ThB), theophylline (ThP), as well as caffeine (CaF) on the basis of the β-type hierarchical structure of the MnO2 nano-flowers (βH-MnO2-NF) modified electrode (βH-MnO2-NF/GCE). Analysis showed an acceptable linear association between the oxidation peak current and ThB, ThP and CaF concentration within the ranges between 0.01 and 320.0 μM with a limit of detection (LOD) equal to 8.7, 5.9, and 10.1 nM (S/N = 3), respectively. Additionally, this study intended to investigate ThB, Thp and CaF bio-availability in the five commercially available brands of the chocolate products and drug.A label-free electrochemical immunosensor based on polyaniline (PANI) micellar electrode was firstly fabricated for direct AMH detection. To control the size regularity of PANI, a micelle-based method using ammonium peroxydisulfate (APS) as a reducing agent was employed in the polymerization process. The Anti-AMH antibodies were readily immobilized onto PANI via peptide bond to enhance the sensor specificity and sensitivity. This sensor was applied for the detection of AMH, an ovarian response indicator in female related to residual eggs during a woman's monthly cycle. The sensor performances were systematically investigated by differential pulse voltammetry. The anodic peak current decreases with the increase of AMH concentration owing to blocking of electron transfer by AMH. Under the optimal conditions, this sensor offers high sensitivity with a low detection limit of 0.1 ng mL-1 and a wide linear range of 0.1-4 ng mL-1, which is sensitive enough to indicate the ability to produce eggs during a woman's monthly cycle. Furthermore, this system requires lower sample volume (5 μL), while offers the simple fabrication with low cost and no synthetic challenge and faster analysis compared with a standard ELISA. Ultimately, this sensor was successfully applied for the detection of AMH in human serum with satisfactory results. Thus, it might be an alternative tool for AMH screening in clinical setting.In the present study we report the simultaneous determination of glutathione (GSH) and glutathione disulfide (GSSG) by an automated flow method based on the concept of zone fluidics. GSH is quantified selectively in a first run by reaction with o-phthalaldehyde at a mildly basic pH = 8, without interference from GSSG. The latter was also found to react with o-phthalaldehyde but in highly basic medium (0.2 mol L-1 NaOH) and was determined after masking of GSH with N-ethyl-maleimide. Detection was carried out fluorimetrically at 340/425 nm. The flow procedure was optimized and validated, paying special attention to its selectivity. The LOD was 60 nmol L-1 for GSH and for 53 nmol L-1 for GSSG, while the within-day and day-to-day precisions were better than 1.5% and 3.7% respectively. Real yeast samples were successfully analyzed without matrix effect (-2.0 to +4.1%) and with percent recoveries being in the range of 87.0 and 103.3%.