Aptamer-based kinetically controlled DNA reactions coupled with metal-organic framework nanoprobes for sensitive detection of SARS-CoV-2 spike protein.

Since the outbreak in 2019, COVID-19, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has become the deadliest infectious disease worldwide for people of all ages, from children to older adults. As a main structural protein of SARS-CoV-2, spike protein is reported to play a key role in the entry of the virus into host cells and is considered as an effective antigenic marker for COVID-19 diagnosis. Herein, we develop a new aptamer-based fluorescence method for SARS-CoV-2 spike protein detection based on using kinetically controlled DNA reactions and metal-organic framework nanoprobes. Specifically, the binding of SARS-CoV-2 spike protein to its aptamer is designed to precisely control the kinetics of a DNA displacement reaction, leading to the release of free signaling probes. By reasonable integration of magnetic enrichment and exonuclease-fuelled recycling, the released probes efficiently disrupt the interaction within metal-organic framework nanoprobes, thereby generating a remarkable fluorescent response. Experimental results show that the method not only exhibits a wide linear range and a low detection limit of 7.8 fg mL-1 for SARS-CoV-2 spike protein detection but also demonstrates desirable specificity and utility in complex samples. Therefore, the method may provide a valuable tool for the detection of SARS-CoV-2 spike protein, and has bright prospects in the rapid diagnosis of COVID-19, which is of great significance for guiding rational treatment during a pandemic of respiratory infectious diseases and reducing the occurrence of severe disease in children.

Magnetite enhancing sludge anaerobic fermentation to improve wastewater biological nitrogen removal: Pilot-scale verification.

Alkaline anaerobic fermentation for acids production has been considered as an effective method to recover resources from waste activated sludge, and magnetite could improve the quality of fermentation liquid. Here, we have constructed a pilot-scale sludge alkaline anaerobic fermentation process enhanced by magnetite to produce short chain fatty acids (SCFAs), and used them as external carbon sources to improve the biological nitrogen removal of municipal sewage. Results showed that the addition of magnetite could significantly increase the production of SCFAs. The average concentration of SCFAs in fermentation liquid reached 3718.6 ± 101.5 mg COD/L, and the average concentration of acetic acid reached 2368.8 ± 132.1 mg COD/L. The fermentation liquid was used in the mainstream A2O process, and its TN removal efficiency increased from 48.0% ± 5.4% to 62.2% ± 6.6%. The main reason was that the fermentation liquid is conducive to the succession of sludge microbial community the denitrification process, increasing the abundance of denitrification functional bacteria and realizing the enhancement of denitrification process. Besides, magnetite can promote the activity of related enzymes to enhance the biological nitrogen removal. Finally, the economic analysis showed that magnetite-enhanced sludge anaerobic fermentation was economically and technically feasible to promote the biological nitrogen removal of municipal sewage.

Characterization and activity of anthocyanins in Zijuan tea (Camellia sinensis var. kitamura).

Zijuan tea is a new cultivar produced in Yunnan province of China. Unlike most tea cultivars, Zijuan tea is anthocyanin-rich. The composition and antioxidant activities of anthocyanins of Zijuan tea were studied for the first time in this paper. Anthocyanins were extracted with acidified methanol and quantified as 707 ± 28 µg/g of dry weight (cyanidin-3-O-ß-D-glucoside equivalent) by high-performance liquid chromatography (HPLC) analysis. Four anthocyanins were successfully identified after Amberlite XAD-7HP adsorption column chromatography and octadecyl silane (ODS) flash chromatography. Among the four, delphinidin-3-O-ß-D-galactoside (1) and cyanidin-3-O-ß-D-galactoside (2) were confirmed by liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS) and HPLC. Delphinidin-3-O-ß-D-(6-(E)-p-coumaroyl) galactopyranoside (3) and cyanidin-3-O-ß-D-(6-(E)-p-coumaroyl) galactopyranoside (4) were characterized by the high-resolution time-of-flight-mass spectrometry (HRTOF-MS) and nuclear magnetic resonance (NMR) spectrometry. The antioxidant activities of compounds 3 and 4, which composed approximately 75% of the total anthocyanins content in HPLC analysis, were evaluated by DPPH and FRAP assays. Results showed that both had higher antioxidant activities than commercial antioxidants butylated hydroxytoluene (BHT) used as one of controls in these assays.

[Determination of protein and gossypol content in cotton kernel powder with near infrared reflectance spectroscopy].

Near-infrared reflectance spectroscopy (NIRS) was used as a rapid and nondestructive method to determine the protein content and gossypol content in cotton kernel powder samples, using 49 upland cotton (Gossypium hirsutum L.) germplasms and 188 recombinant inbred lines (RILs). The cottonseed samples harvested from the upland cotton germplasms and RILs grown in different cotton growing regions in different years were analyzed chemically for protein and gossypol contents, as well as scanned in the reflectance mode of a scanning monochromator. Using ISI software for scanning and data analysis, protein and gossypol calibration equations were obtained with a standard normal variate + detrending scatter correction and a 2, 4, 4, 1 math treatment and modified partial least square (MPLS) as the regression method. The protein content calibration results revealed that the multiple correlation coefficients (RSQ) and statistic 1--variance ratio (1-VR) for the determination of protein content in cottonseed kernels were 0.933 and 0.929, respectively, and its standard error of calibration (SEC) and standard error of cross validation (SECV) were 0.623 and 0.638, respectively. As the calibration equations were judged by the calibration RSQ (or 1-VR) and SEC (or SECV), the results indicated that NIRS is comparable to chemical methods in both accuracy and prediction and is reliable in the determination of protein content in cottonseed kernels. However, the RSQ, SEC, 1-VR and SECV for gossypol content determination of NIRS were 0.836, 0.811, 0.074 and 0.079, respectively. Although it was weaker than that of protein content, the NIRS method is still good enough for the determination and prediction of the gossypol content in cottonseed kernels. Therefore, NIRS models were successfully developed for protein content and gossypol content analysis of cotton kernel powder sample in the present study and they could be introduced into the cotton germplasm evaluation and breeding program for the cottonseed quality improvement.