Non-pyrolytic synthesis of laccase-like iron based single-atom nanozymes for highly efficient dual-mode colorimetric and fluorescence detection of epinephrine.

Single-atom nanozymes have garnered significant attention due to their exceptional atom utilization and ability to establish well-defined structure-activity relationships. However, conventional pyrolytic synthesis methods pose challenges such as high energy consumption and random local environments at the active sites, while achieving non-pyrolytic synthesis of single-atom nanozymes remains a formidable technical hurdle. The present study focuses on the synthesis of laccase-like iron-based single-atom nanozymes (Fe-SAzymes) using a non-pyrolysis method facilitated by microwave irradiation. Under low iron loading conditions, Fe-SAzymes exhibited significantly enhanced laccase activity (12.1 U/mg), surpassing that of laccase by 24-fold. Moreover, Fe-SAzymes demonstrated efficient catalytic oxidation of epinephrine (EP), enabling its colorimetric detection. Owing to the remarkable laccase activity of Fe-SAzymes, the conventional nanozymes EP detection time was reduced from 60 min to 20 min, with an impressive low detection limit as low as 2.95 µM. In addition, an ultra-sensitive fluorescence method for EP detection was developed using the internal filter effect of EP oxidation products and CDs combined with carbon dots probe. The detection limit of fluorescence method was only 0.39 µM. Therefore, an visual, fast, and highly sensitive dual-mode EP detection strategy has great potential in the clinical diagnostic industry.

Colorimetric sensor array for identifying antioxidants based on pyrolysis-free synthesis of Fe-N/C single-atom nanozymes.

Iron-anchored nitrogen/doped carbon single-atom nanozymes (Fe-N/C), which possess homogeneous active sites and adjustable catalytic environment, represent an exemplary model for investigating the structure-function relationship and catalytic activity. However, the development of pyrolysis-free synthesis technique for Fe-N/C with adjustable enzyme-mimicking activity still presents a significant challenge. Herein, Fe-N/C anchored three carrier morphologies were created via a pyrolysis-free approach by covalent organic polymers. The peroxidase-like activity of these Fe-N/C nanozymes was regulated via the pores of the anchored carrier, resulting in varying electron transfer efficiency due to disparities in contact efficacy between substrates and catalytic sites within diverse microenvironments. Additionally, a colorimetric sensor array for identifying antioxidants was developed: (1) the Fe-N/C catalytically oxidized two substrates TMB and ABTS, respectively; (2) the development of a colorimetric sensor array utilizing oxTMB and oxABTS as sensing channels enabled accurate discrimination of antioxidants such as ascorbic acid (AsA), glutathione (GSH), cysteine (Cys), gallic acid (GA), and caffeic acid (CA). Subsequently, the sensor array underwent rigorous testing to validate its performance, including assessment of antioxidant mixtures and individual antioxidants at varying concentrations, as well as target antioxidants and interfering substances. In general, the present study offered valuable insights into the active origin and rational design of nanozyme materials, and highlighting their potential applications in food analysis.

Whole-brain in vivo base editing reverses behavioral changes in Mef2c-mutant mice.

Whole-brain genome editing to correct single-base mutations and reduce or reverse behavioral changes in animal models of autism spectrum disorder (ASD) has not yet been achieved. We developed an apolipoprotein B messenger RNA-editing enzyme, catalytic polypeptide-embedded cytosine base editor (AeCBE) system for converting C·G to T·A base pairs. We demonstrate its effectiveness by targeting AeCBE to an ASD-associated mutation of the MEF2C gene (c.104T>C, p.L35P) in vivo in mice. We first constructed Mef2cL35P heterozygous mice. Male heterozygous mice exhibited hyperactivity, repetitive behavior and social abnormalities. We then programmed AeCBE to edit the mutated C·G base pairs of Mef2c in the mouse brain through the intravenous injection of blood-brain barrier-crossing adeno-associated virus. This treatment successfully restored Mef2c protein levels in several brain regions and reversed the behavioral abnormalities in Mef2c-mutant mice. Our work presents an in vivo base-editing paradigm that could potentially correct single-base genetic mutations in the brain.

A fluorescent carbon dots synthesized at room temperature for automatic determination of nitrite in Sichuan pickles.

In this paper, highly fluorescent carbon dots were synthesized from sodium ascorbate and polyethyleneimine at room temperature (R-CDs). The proposed green synthesis method was energy-saving, environmentally friendly and easy online. R-CDs exhibit an optimal emission peak of 490 nm under excitation at 380 nm with a quantum yield of 32 %. R-CDs morphology, composition, and properties were characterized using TEM, FTIR, XPS, UV-vis and fluorescence spectroscopy. The study revealed that nitrite quenched the fluorescence of R-CDs under acidic conditions. Subsequently, this discovered reaction of R-CDs and nitrite was combined with flow-injection technology, and a simple, precise and automatic fluorescence strategy for nitrite determination was accomplished. The response to nitrite was linear in 5-300 µg·L-1 concentration range and the limit of detection was 2.85 µg·L-1 (3.3 S/k). This method was applied to nitrite determination in Sichuan pickles during the pickling process and results were consistent with the standard method, demonstrating its feasibility in practical applications.

Flow injection spectrophotometric determination total antioxidant capacity in human serum samples based on response surface methodology to optimize synthesized peroxidase-like activity carbon dots.

Total antioxidant capacity (TAC) is an important indicator for evaluating oxidative stress of the human body. Since TAC is related to the concentration of reducing substances, it can be detected by using peroxidase-like or oxidase-like activity of nanozyme materials. In this work, the cobalt and nitrogen co-doped carbon dots (Co/N-CDs) are fabricated for building stability and high peroxidase-like nanozyme through the Box-Behnken design of response surface methodology. The morphology and luminescence properties of obtained Co/N-CDs were characterized by TEM and fluorophotometer, respectively. Interestingly, the surface charge of Co/N-CDs are innovatively investigated by a simple and widespread gel electrophoresis, which holds the potential to be an alternative to Zeta potential analysis. In addition, a flow injection spectrophotometric assay to detect ascorbic acid is develop with a high sensitivity and automation based on a Co/N-CDs/guaiacol/H2O2 catalytic reaction system. The proposed method is also responsive to other reducing substances such as cysteine and glutathione. Therefore, the presented sensor can realize the determination of TAC, and then, some actual human serum samples are detected accurately and quickly (the recovery rates are 93.46-105.61 %).

Oridonin Induces Apoptosis of Laryngeal Carcinoma via Endoplasmic Reticulum Stress.

PURPOSE: Oridonin, a bioactive diterpenoid derived from Rabdosia rubescens, has been widely reported to exhibit anticancer activity in multiple types of cancer. However, the molecular mechanism of oridonin in human laryngeal carcinoma has not been clearly elucidated. This study investigated the function of oridonin in laryngeal carcinoma to provide a research basis for laryngeal carcinoma therapy. METHODS: The proliferation of laryngeal carcinoma Hep-2 and TU212 cells treated with oridonin was determined by MTT assay. The apoptotic induction effect of oridonin on Hep-2 and TU212 cells was analyzed by flow cytometry, Western blot analysis and caspase3 activity assay. In addition, the caspase inhibitor, Z-VAD-fmk, was synergistically treated with oridonin to detect the function of caspase cascade in oridonin-mediated apoptosis. Then, the expressions of endoplasmic reticulum (ER) stress-related proteins (GRP78, phosphorylated-PERK, phosphorylated-eIF2α and CHOP) were measured in Hep-2 and TU212 cells by Western blotting. The cells were treated with 4-PBA (an ER stress inhibitor) or knockdown of CHOP to explore the role of ER stress in oridonin-mediated apoptosis in laryngeal carcinoma. Subsequently, a nude mouse xenograft model was constructed to confirm the function of oridonin in laryngeal carcinoma in vivo. RESULTS: Oridonin was found to significantly inhibit the proliferation of laryngeal carcinoma Hep-2 and TU212 cells in a concentration-dependent manner. Then, we confirmed that oridonin could induce apoptosis in human laryngeal carcinoma cells. The caspase inhibitor, Z-VAD-fmk, could partially reverse the pro-apoptotic effect of oridonin on human laryngeal carcinoma cells. Subsequently, Western blotting analysis demonstrated that endoplasmic reticulum (ER) stress-related proteins (GRP78, phosphorylated-PERK, phosphorylated-eIF2α and CHOP) were up-regulated in Hep-2 and TU212 cells exposed to oridonin. In addition, 4-PBA (an ER stress inhibitor) or knockdown of CHOP could antagonize oridonin-induced apoptosis. Oridonin significantly decreased the tumorigenicity of Hep-2 cells in a nude mouse xenograft model. CONCLUSION: Oridonin-induced apoptosis of human laryngeal carcinoma through the activation of ER stress.