Mccollumsteffensen3295

The anion-exchange selectivity in aqueous media is reversed by a use of an aprotic solvent, such as acetonitrile (MeCN). Hence, we have come up with the idea of preconcentrating anions in MeCN and stripping them with an aqueous mobile phase for IC analysis. The introduction of the IL component anions into the IC separation column is substantially reduced while maintaining high sensitivity for the halide impurities. Sub μM impurities are detectable in the mM level of ILs.The spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has led to the outbreak of the 2019 coronavirus (COVID-19) disease, which greatly challenges the global economy and health. Simple and sensitive diagnosis of COVID-19 at the early stage is important to prevent the spread of pandemics. Herein, we have proposed a target-triggered cascade signal amplification in this work for sensitive analysis of SARS-CoV-2 RNA. Specifically, the presence of SARS-CoV-2 RNA can trigger the catalytic hairpin assembly to generate plenty of DNA duplexes with free 3'-OH termini, which can be recognized and catalyzed by the terminal deoxynucleotidyl transferase (TdT) to generate long strand DNA. The prolonged DNA can absorb substantial Ru(NH3)63+ molecules via electrostatic interaction and produce an enhanced current response. The incorporation of catalytic hairpin assembly and TdT-mediated polymerization effectively lowers the detection limit to 45 fM, with a wide linear range from 0.1 pM to 3000 pM. see more Moreover, the proposed strategy possesses excellent selectivity to distinguish target RNA with single-base mismatched, three-base mismatched, and random sequences. Notably, the proposed electrochemical biosensor can be applied to analyze targets in complex circumstances containing 10% saliva, which implies its high stability and anti-interference. Moreover, the proposed strategy has been successfully applied to SARS CoV-2 RNA detection in clinical samples and may have the potential to be cultivated as an effective tool for COVID-19 diagnosis.We have designed and prepared an electrochemical biosensor for lactate determination. Through a diazotation process, the enzyme lactate oxidase (LOx) is anchored onto chevron-like graphene nanoribbons (GNR), previously synthesized by a solution-based chemical route, and used as modifiers of glassy carbon electrodes. In a first step, we have performed the grafting of a 4-carboxyphenyl film, by electrochemical reduction of the corresponding 4-carboxyphenyl diazonium salt, on the GNR-modified electrode surface. In this way, the carboxylic groups are exposed to the solution, enabling the covalent immobilization of the enzyme through the formation of an amide bond between these carboxylic groups and the amine groups of the enzyme. The biosensor design was optimized through the morphological and electrochemical characterization of each construction step by atomic force microscopy, scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy.The cyclic voltammetric response of the biosensor in a solution of hydroxymethylferrocene in presence of l-lactate evidenced a clear electrocatalytic effect powered by the specific design of the biosensing platform with LOx covalently attached to the GNR layer. From the calibration procedures employed for l-lactate determination, a linear concentration range of 3.4 · 10-5- 2.8 · 10-4 M and a detection limit of 11 μM were obtained, with relative errors and relative standard deviations less than 6.0% and 8.4%, respectively. The applicability of the biosensor was tested by determining lactate in apple juices, leading to results that are in good agreement with those obtained with a well-established enzymatic spectrophotometric assay kit.It is important to establish a sensitive and rapid screening detection method for Florfenicol (FF) residue in eggs. A magnetic relaxation switch (MRS) and colorimetric aptasensor were developed for the detection of FF based on aptamer-modified Au@Fe3O4 nanoparticles (NPs). Apt-Au@Fe3O4 NPs were played as a "switch" between dispersion and aggregation, with a concomitant change in the R2 (T2 relaxivity, 1/T2W) and the UV-vis absorption spectra. To improve the sensitivity and stability of the method, the aptamers modification, salt inducing aggregation, and reaction conditions were optimized. The molar ratio of aptamers to Au, the incubation time of aptamers modification, the molar ratio of NaCl to Au, the dilute ratio of Apt-Au@Fe3O4, and reaction time were optimized to be 21, 3 h, 151, 1300 and 15 min, respectively. The working range and LOD of MRS analysis are 0.1-10 nM and 1.10 nM for Florfenicol amine (FFA), 4-40 nM and 5.65 nM for FF. Noticeably, the colorimetric analysis can also qualitatively analyze the FF and FFA. The working ranges and LOD were 5-40 μM (5 μM) and 10-40 μM (10 μM), respectively. Hence, the results indicated that this aptasensor could be a potential tool for the rapid detection of FF residue in food.The chemistry of the metal-organic frameworks (MOFs) coating may affect the biological functionality of the encapsulated biomacromolecules in harsh environment. Enzymes encapsulated in hydrophilic MAF-7 can retain high activity in harsh environment. We conducted this study to prepare a non-invasive wearable uircase@MAF-7-based electrochemical sensor that can achieve accurate and sensitive detection of UA levels in sweat by integrating a flexible microfluidic chip and wireless electronic readout device. The flexible microfluidic chip enabled an easy and effective collection of sweat samples. MAF-7 protected enzyme activity by encapsulating uricase. The uricase@MAF-7-based electrochemical sensor enabled the highly sensitive detection of UA in the concentration range of 2 μM-70 μM with a detection limit of as low as 0.34 μM. Additionally, we evaluated the utility of the sensor for monitoring UA levels in real sweat samples by means of a high purine dietary challenge. This personalized wearable sweat sensing device has a potential to be used for monitoring disease-related metabolites in daily life.Herein, an antifouling electrochemical biosensor based on designed multifunctional peptides with two recognizing branches specific for one target was proposed to improve the target recognition efficiency and sensitivity. The designed multifunctional peptide contains two different recognizing branches (with sequences FYWHCLDE and FYCHTIDE) for immunoglobulin G (IgG), an antifouling sequence (EKEKEK) and an anchoring sequence (CPPPP), which can be immobilized onto the gold nanoparticles (AuNPs) and poly(3,4-ethylenedioxythiophene) (PEDOT) modified electrode surface. Owing to the synergistic effect of the two recognizing branches, the dual-recognizing peptide-based biosensor exhibited significantly enhanced sensitivity. Under the optimal experimental conditions, the biosensor for IgG exhibited a linear response range of 0.1 pg/mL to 0.1 μg/mL, with a limit of detection of 0.031 pg/mL (about 2 orders of magnitude lower than that of the normal biosensor). Moreover, the biosensor was also capable of assaying IgG in real biological samples such as human serum without suffering from significant biofouling. This strategy for biosensor construction not only ensures the ultra-sensitivity for target detection, but also effectively avoids biofouling on sensing interfaces in complex biological media.The development of methods to realize the on-site analysis of antibiotic pollutants is of great importance for food quality control and environmental monitoring. Herein, we designed a magnetic bead (MB)-based DNA walker and utilized its target-triggered and endonuclease-driven walking reaction to develop a novel colorimetric and electrochemical dual-mode biosensing method for the convenient detection of kanamycin (Kana) antibiotic. The colorimetric signal transduction strategy of the method was constructed on the telomerase extension of the DNA walking-released telomeric primer into G-quadruplex/hemin DNAzymes. Due to the DNA walking and telomerase dual signal amplification, a good linear relationship from 0.1 pg mL-1 to 1 ng mL-1 was obtained for this strategy with a detection limit of 22 fg mL-1. Meanwhile, the MB complex produced through the above DNA walking reaction was also used as a multipedal DNA walker to develop an electrochemical signal transduction strategy. By utilizing it to trigger another endonuclease-driven DNA walking at a DNA hairpin-modified electrode, ferrocene labels were quantitatively released from this electrode to cause the electrochemical signal decrease. Because of the dual endonuclease-driven DNA walking for signal amplification, a five-order of magnitude wide linear relationship from 0.01 pg mL-1 to 1 ng mL-1 was obtained with an ultralow detection limit of 8.4 fg mL-1. As the two strategies did not involve complicated manipulations and the requirement of expensive instruments, this biosensing method exhibits a high application value for the on-site semiquantitative screening and accurate analysis of antibiotic residues.C-peptide is a biomarker that has clinical implications for the diagnosis of a variety of diseases. In this study, an ultrasensitive time-resolved fluorescence lateral flow immunochromatographic assay (TRF-LFIA) method was established for the detection of C-peptides in human serum. The key to this method is the oriented immobilization of antibodies anti C-peptide on TRF microspheres that can sufficiently expose the antigen binding site. The limit of detection (LOD) of this method for C-peptide was 0.005 ng mL-1, which is 10-fold less than that of TRF-LFIA method based on nonoriented immobilizing antibodies. The working range of this method was 0.005-250 ng mL-1, and the spiked recoveries of C-peptide in human serum were 106.85%-116.40% with a CV value less than 10%. The test results of actual serum samples had good consistency (R2 > 0.97) with the Roche Cobas 8000 automatic chemiluminescence immunoassay analyzer. This method can be utilized for the point-of-care testing (POCT) of C-peptide, and the oriented immobilizing method can also be used to construct highly sensitive probes to improve the sensitivity of other analytes in the POCT platform.Food additives are essential to guarantee processed foods' safety throughout its journey from workshops or factories to shops or catering establishment and eventually to consumers. As one of the commonly-used food additives, nitrites upon reaction with amines would generate highly toxic nitrosamines (e.g., N,N-diethylnitrosamine, DEN) as inadvertent byproducts resulted from food processing or preparation which are known to cause hepatotoxicity and even cancer. Hence detecting nitrosamine-induced acute liver injury accurately would be conducive to planning optimal treatment and avoid any further deterioration. Herein we design an activatable probe (BHC-Lut) that can release the drug luteolin for therapy and the chromophore (BHC-OH) for NIR-II fluorescence/optoacoustic imaging upon being triggered by hepatic biomarker hydrogen peroxide. In the probe BHC-Lut, benzoindolium heptamethine cyanine with NIR-II fluorescent emission is adopted as the chromophore scaffold, the incorporation of triethylene glycol into benzoindolium ensures sufficient water solubility and enhances biocompatibility of the probe, and luteolin is coupled onto the chromophore via boronate linkage that acts as both H2O2-responsive unit and the fluorescence quencher.