The emergence and spread of 2019 novel coronavirus–infected pneumonia (COVID‐19) from Wuhan, China, it has spread globally. We extracted the data on 14 patients with laboratory‐confirmed COVID‐19 from Jinhua Municipal Central hospital through 27 January 2020. We found that compared to pharyngeal swab specimens, nucleic acid detection of COVID‐19 in fecal specimens was equally accurate. And we found that patients with a positive stool test did not experience gastrointestinal symptoms and had nothing to do with the severity of the lung infection. These results may help to understand the clinical diagnosis and the changes in clinical parameters of COVID‐19.
A novel nanocomposites gel was prepared by neutralizing a designer nanocomposites solution of chitosan encapsulated gold nanoparticles formed by reducing in situ tetrachloroauric acid in chitosan. The bio-inspired gel was designed for immobilization and electrochemical study of cells and monitoring adhesion, proliferation, and apoptosis of cells on electrodes. Using K562 leukemia cells as a model, an impedance cell sensor was constructed. The methods for preparation of the gel and immobilization of cells were simple and "green". The nanocomposites gel showed improved immobilization capacity for cells and good biocompatibility for preserving the activity of immobilized living cells. The living cells immobilized on glassy carbon electrode exhibited an irreversible voltammetric response and increased the electron-transfer resistance with a good correlation to the logarithmic value of concentration ranging from 1.34 x 10(4) to 1.34 x 10(8) cells mL-1 with a limit of detection of 8.71 x 10(2) cells mL-1 at 10sigma. This work implied that the nanocomposites gel based on biopolymer and nanoparticles possessed potential applications for biosensing and provided a new avenue for electrochemical investigation of cell adhesion, proliferation, and apoptosis.
A highly sensitive competitive immunosensor based on the electrochemiluminescence (ECL) of quantum dots (QDs) was proposed by coupling with an enzymatic amplification. The fabrication process of the immunosensor was traced with atomic force microscopic images and electrochemical impedance spectra. The strong cathodic ECL emission of the immobilized QDs could be detected at a relatively low emission potential. The reduction of dissolved oxygen during the cathodic process provided a self-produced coreactant, H(2)O(2), for the ECL emission. Using human IgG (HIgG) as a model protein, upon the immuno-recognition of the immobilized HIgG to its antibody labeled simply with horseradish peroxidase, the ECL intensity decreased due to the steric hindrance of the proteins to electron transfer. The decrease could be greatly amplified by an enzymatic cycle to consume the self-produced coreactant, leading to a wide calibration range of 0.05 ng mL(-1) approximately 5 microg mL(-1) and a low limit of detection for the competitive immunoassay of HIgG. This immunosensor showed good stability and fabrication reproducibility. The immunoassays of practical samples showed acceptable results. This facile immunosensing strategy opened a new avenue for detection of proteins and application of QDs in ECL biosensing.
A newly designed molecularly imprinted polymer (MIP) material was developed and successfully used as recognition element to fabricate a capacitive sensor for enantioselective recognition of glutamic acid (Glu). The MIP with a well‐defined structure was synthesized on a gold electrode in one step by electrochemical copolymerization of o‐phenylenediamine (o‐PD) and dopamine (DA) in the presence of template molecule Glu. The resulting MIP material was characterized with a potentiostatic frequency scan method, cyclic voltammetry, capacitance measurements, atomic force microscopy, and X‐ray photoelectron spectroscopy. The structure and recognition behaviour of the copolymer film to template molecule depended on its composition. The optimal composition was at the o‐PD to DA molar ratio of 3:2. With a potentiostatic time scan method the copolymer displayed high enantioselectivity and sensitivity to the stereoselective rebinding of L‐ or D‐Glu to their corresponding artificial receptor due to the exact definition of the imprint cavity. The capacitance response of the sensor for L‐Glu or D‐Glu was proportional to their concentration in the range of 16.7 to 250 μM. The enantiometric selectivity coefficients for L‐Glu and D‐Glu imprinted films against their respective enantiomers are 24 and 15, respectively. The resulting MIP capacitive sensors showed good reproducibility, stability and repeatability. This strategy opened a convenient way for preparation of enantioselective MIPs and recognition of enantiotropic molecules.
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