Iron, cobalt and nitrogen co-doped carbon dots (FeCo/N-CDs) were fabricated firstly by a one pot hydrothermal method in this study. As well as exhibiting peroxidase-like activity, the prepared FeCo/N-CDs emitted fluores-cence at 475 nm upon the excitation of 360 nm. A dual-signal biosensor relied on ratiometric fluorescence and colorimetric method was developed for detecting uric acid (UA) based on FeCo/N-CDs-catalyzed oxidation of OPD. Uricase catalyzed the production of H2O2 from UA, and FeCo/N-CDs catalyzed H2O2 into the & BULL;OH radicals, contributing to the oxidation of 2,3-diaminophenazine (DAP) from o-phenylenediamine (OPD). The color from colorless to yellow was observed and DAP can quench the fluorescence of FeCo/N-CDs via the inner filter effect (IFE), accompanied with a significant fluorescence enhancement of DAP at 580 nm. The fluorescence emission and UV-vis absorption intensities were thus affected by sequential additions of UA. Quantitative analysis of UA was based on the fluorescence intensity of DAP/FeCo/N-CDs (I580/I475) and color records. The calibration curve was linear within the range of 0.2-150 mu M and the limit of detection was low as 0.05 mu M. The biosensor was successfully applied to the detection of UA in serum and urine samples.

Herein, a sensing platform for the rapid quantitative detection of glyphosate with high sensitivity and selectivity was constructed by enzyme-free ratiometric fluorescence and colorimetric dual read-out assay based on ultrathin g-C3N4 nanosheets (UCN NS). Fluorescent diaminophenylazine (DAP) with fluorescence was from the oxidation of o-phenylenediamine (OPD) in the presence of Cu2+. DAP could inspire a significant fluorescence quenching of nanosheets due to photo-induced electron transfer (PET), therefore exhibiting a ratiometric fluorescence response. In the presence of glyphosate, the strong chelation of Cu2+ by glyphosate inhibited the oxidation of OPD, which reduced the fluorescence intensity of DAP, while the fluorescence of the ultrathin nanosheets was restored. Moreover, the oxidation of OPD (colorless) to DAP (yellow) was a distinctly visible color change process, which provides well-suited conditions for colorimetric analysis. At the optimum experimental conditions, the detection concentration range of glyphosate was 0.001-0.48 mu g/mL, and the limit of fluorometric detection was 0.49 ng/mL (S/N = 3). This assay was simple and easy to use for the detection of glyphosate in food safety and the environment with satisfactory results.

Public health emergencies will pose an enormous challenge to healthcare service systems. As COVID-19 rage across the globe, we realize that COVID-19 exposes the problem of inadequate research on the dispatch of emergency medical personnel in response to a major epidemic outbreak. In the face of major public health emergencies, failure in timely satisfaction of healthcare demands by local healthcare professionals necessitates human resource support from other regions. To address this issue, further research is needed to gain better insights into interregional emergency human resource allocation. This paper aims to offer attention to patients’ medical needs and suppose that there are support hubs outside the outbreak region offering an external supply of medical personnel. The hospitals in these support hubs are categorized based on variables such as capacity, medical capability, and the number of dispatched personnel per day. An interregional emergency allocation model was established to consider the proper doctor-patient ratio and nurse-patient ratio in emergency response using methods such as mathematical programming. And relevant management suggestions were then offered via analysis. Research in this paper provides allocation models and proposals that healthcare professionals can refer to when making resource allocation decisions in emergency response.

In this study, we have developed a sensitive approach to measure organophosphorus pesticides (OPs) using graphitic-phase C3N4 nanosheets (g-C3N4) combined with a nanomaterial-based quencher, MnO2 nanosheets (MnO2 NS). Since MnO2 NS can quench the fluorescence of g-C3N4 via the inner-filter effect (IFE), enzymatic hydrolysate (thiocholine, TCh) can efficiently trigger the decomposition of MnO2 nanosheets in the presence of acetylcholinesterase (AChE) and acetylthiocholine (ATCh), resulting in the fluorescence recovery of g-C3N4. OPs, as inhibitors to AChE activity, can prevent the generation of TCh and decomposition of MnO2 nanosheets while exhibiting fluorescence quenching. Therefore, the AChE-ATCh-MnO2-g-C3N4 system can be utilized to quantitatively detect OPs based on g-C3N4 fluorescence. Under optimal conditions, the linear ranges for the determination of parathion-methyl (PM) and 2,2-dichlorovinyl dimethyl phosphate (DDVP) were found to be 0.1-2.1 ng/mL and 0.5-16 ng/mL, respectively, with limits of detection of 0.069 ng/mL and 0.20 ng/mL, respectively. The advantages of this assay are user-friendliness, ease of use, and cost effectiveness compared to other more sophisticated analytical instruments.

In this work, the mechanism of the effect of lipid oxidation on the IgG/IgE binding ability of ovalbumin (OVA) was investigated via the peroxyl radicals produced by 2, 2'-azobis (2-amidinopropane) dihydrochloride to simulate lipid oxidation. Results showed that the structure of OVA unfolded partially with an increase in oxidation degree, leading to the exposure of the allergenic epitopes and increasing the IgG/IgE binding ability of OVA. Nine oxidation sites were found on the α-helix, and these sites may unwind the α-helix and expose the allergenic epitopes on the OVA surface, leading to antibody recognition and combination. Consequently, the IgG/IgE binding ability of OVA was increased. In conclusion, the allergenic capacity of OVA can be promoted by modifying peroxyl radical oxidation in processing egg products.

Ovalbumin (OVA) is one of the major food allergens in hen eggs. In this work, it was demonstrated that glycation with d-glucose and its epimers, including d-mannose, d-allose, d-galactose, and l-idose, could effectively attenuate the IgG/IgE binding of OVA, which was attributed to the covalent masking by sugars and to its structural changes. The glycation sites were determined, and their average degree of substitution was found using liquid chromatography coupled with high-resolution mass spectrometry. Fluctuations in OVA conformation were monitored by conventional spectrometry. Compared to those of OVA-Man and OVA-Glu, OVA-All, OVA-Gal, and OVA-Ido showed a higher glycation extent, and the alterations on their steric layouts were more drastic, suggesting that the configuration of hydroxyl groups at positions C-3, C-4, and C-5 in sugars might be important for the glycation reactivity; as such, their capabilities in binding with IgG/IgE decreased more significantly. Attempts were made to provide valuable information for in-depth understanding of the differences in biochemical functionality among epimeric sugars. These insights would be helpful for designing sweetened food products with a desirable level of safety.

Glycation between ovalbumin (OVA) and different monoses under mild dry heating at 37 °C was studied. The content of free amino groups decreased dramatically, and the conformational changes based on fluorescence and circular dichroism spectra were evident in glycated OVA. The glycated sites and the average degree of substitution per peptide molecule per site were determined using liquid chromatography high-resolution mass spectrometry. Lysine and arginine were the predominant glyaction sites, in which Lys207 was a relatively reactive site for glycation in all of the conjugates. In general, the extent of glycation of aldose was higher, and its alterations on the steric layouts of protein were more drastic than those of ketose. The configuration of hydroxyl groups at C-4 in sugar epimers might be important for the glycation reactivity and conformational modification in the glycated proteins. These insights would have important implications for the creation of sweetened food products with desirable structures and excellent quality control.