A colorimetric detection of dopamine in urine and serum based on the CeO2 @ZIF-8/Cu-CDs laccase-like nanozyme activity.

This study reports a sensitive and selective colorimetric approach for the analysis of dopamine (DA) based on CeO2 @ZIF-8/Cu-CDs laccase-like nanozymes activity. The CeO2 @ZIF-8/Cu-CDs was synthesized using cerium oxide (CeO2 ) and copper-doped carbon dots (Cu-CDs) with 2-methylimidazole by a facilely hydrothermal approach. The CeO2 @ZIF-8/Cu-CDs exhibited excellent laccase-like nanozymes activity and can oxidize the colorless substrate (DA) to red product with 4-aminoantipyrine as the chromogenic agent. The Michaelis-Menten constant (Km ) and the maximal velocity (Vmax ) of CeO2 @ZIF-8/Cu-CDs are 0.20 mM and 1.48 µM/min, respectively. The detection method has a linear range of 0.05-7.5 µg/mL and a detection limit as low as 8.5 ng/mL with good reproducibility. The developed colorimetric sensor was applied to rapid and precise quantitative evaluation of DA levels in serum and urine samples. This study presents a new approach for detecting biological molecules by utilizing the controlled regulation of nanozymes' laccase-like activity.

Cu, I-doped carbon dots as simulated nanozymes for the colorimetric detection of morphine in biological samples.

As newly developed synthetic enzymes with exceptional catalytic capabilities and outstanding stability, nanozymes have drawn considerable interest in the realm of sensing. Using a simple hydrothermal process, iodine and copper-doped carbon dots (Cu,I-CDs) with simulated enzymes were fabricated in the current investigation. Cu,I-CDs demonstrate peroxidase-mimicking function together with high catalytic effectiveness due to aforementioned features. This led to generation of a colorimetric sensor for quick and accurate quantitative assessment of morphine (MOR). The outcomes showed the method's usefulness for the colorimetric detection of MOR. The linear range for MOR detection is 0.25-25 µg/mL having a reduced detection limit of 64 ng/mL. This sensor's successful use in the analysis of MOR in biological material is more noteworthy.

Theoretical Study on the Formation and Decomposition Mechanisms of Coelenterazine Dioxetanone.

Bioluminescence has been drawing broad attention due to its high signal-to-noise ratio and high bioluminescence quantum yields, which has been widely applied in the fields of biomedicine, bioanalysis, and so on. Among numerous bioluminescent substrates, coelenterazine is famous for its wide distribution. However, the oxygenation reaction mechanism of coelenterazine is far from being completely understood. In this paper, the formation and decomposition mechanisms of coelenterazine dioxetanone were investigated via density functional theory (DFT) and time-dependent (TD) DFT approaches. The results showed that the oxygenation reaction first occurred along the triplet-state potential energy surface (PES), after the intersystem crossing (ISC), second jumped to the diradical-state PES, and ultimately formed coelenterazine dioxetanone. For the decomposition mechanism of dioxetanone, the computational results showed that the chemiexcitation of neutral dioxetanone was more efficient than that of other dioxetanone species. Moreover, the diradical properties and the degree of ionic character are modified by the counter ions.

Dual-Emission Carbon-Dot Ratiometric Fluorescence Sensor for Morphine Recognition in Biological Samples.

Herein, a novel nitr[ogen-doped carbon dot (N-CD) fluorescence sensor with a dual emission ratio is developed using the microwave-assisted synthesis of m-phenylenediamine and spermidine. As a result of the fluorescence inner filtration effect (IFE) effect between morphine (MOR) and N-CD, the blue fluorescence of N-CDs at 350 nm was reduced in the presence of MOR, whereas the fluorescence of N-CDs at 456 nm increased substantially. The results demonstrated that the approach has a tremendous potential and that the linear range of MOR detection is 0.25-25 µg/mL, with a 71.8 ng/mL detection limit. Under UV light, the blue fluorescent system is easily visible to the naked eye. More significantly, the sensor proved successful in providing satisfactory results for the speciation measurement of MOR in a variety of biological samples.

Novel N,Cl-doped deep eutectic solvents-based carbon dots as a selective fluorescent probe for determination of morphine in food.

In the present study, new N,Cl co-doped carbon dots (N,Cl-CDs) based on deep eutectic solvent (DES) were fabricated by a facile hydrothermal process. This fluorescent probe exhibited a good quantum yield of 14% and was applied for the sensitive and selective quantification of morphine in foods. In addition, the influence of solution pH, interaction time, system temperature, interfering substances and analogues on the determination was also investigated. Under the optimized conditions, the luminescence intensity of carbon dots increased linearly with the addition of morphine in the concentration range of (0.15-280.25) µg mL-1 (R 2 > 0.9969) and the limit of detection (LOD) of 46.5 ng mL-1. Based on these results, it is suggested that N,Cl-CDs is a promising fluorescent probe for sensitive and selective quantification of morphine in foods.

Comprehensive Investigation of Moringa oleifera from Different Regions by Simultaneous Determination of 11 Polyphenols Using UPLC-ESI-MS/MS.

In this study, we develop and validate a simultaneous quantification of polyphenols method based on an ultra-performance liquid chromatography-electrospray ionization-tandem mass spectrometry (UPLC-ESI-MS/MS) to adequately understand how different habitats influence the quality and profile of Moringa oleifera polyphenol. Furthermore, principal component analysis (PCA) and hierarchical cluster analysis (HCA) were used to compare and discriminate 25 samples collected from different areas. A significant correlation was found between the polyphenol profile and the collection area. Significant differences in the polyphenol content of Moringa oleifera from different regions indicate that the genetic diversity of Moringa oleifera was relatively rich, possibly due to differences in cultivation conditions, climate, or soil environment resulting in the accumulation of different polyphenols. These observations provide a theoretical basis for subsequent Moringa oleifera germplasm selection and development research. Furthermore, the quantitative analysis methodology used to characterize the polyphenols may be used toward developing quality assessment and future pharmacodynamic investigations of Moringa oleifera.

Screening of multiclass pesticide residues in maca and Moringa oleifera by a modified QuEChERS sample preparation procedure and UPLC-ESI-MS/MS analysis.

In the present study, a modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) method was proposed for the simultaneous analysis of 75 pesticides in maca and Moringa oleifera with ultra-performance liquid chromatography-electrospray ionization-tandem mass spectrometry (UPLC-ESI-MS/MS). The developed method was validated in accordance with linearity, linear range, limit of detection, limit of quantification, accuracy, precision, and matrix effect. Each analyte had good linearity (R 2 > 0.99) in the corresponding concentration range. The method LOD and LOQ values of all the analytes ranged from 0.01 µg kg-1 to 303.35 µg kg-1 and 0.03 µg kg-1 to 1011.15 µg kg-1, respectively. The recoveries (n = 6) of the analyzed pesticides were in the range of 75.92-113.43%. The RSDs of precision were between 0.60% and 7.36%. All matrix effect values ranged from 81.79% to 118.71% and 80.36% to 119.64% in maca and Moringa oleifera, respectively. The analysis of 103 samples showed the presence of isofenphos-methyl in some of them. The method had a good application prospect and could be used as a general approach for the quantitative determination of pesticide residues in food.