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

An ultrasensitive colorimetric/fluorescent/photothermal sensing platform for the detection of D-amino acids based on carbon dots nanozymes with enhanced peroxidase-like activity

Based on the enhanced peroxidase-like activity of carbon dots nanozymes (CDszymes), with a specific oxidation reaction of D-amino acid oxidase catalysing the formation of H2O2 from D-amino acid, an ultrasensitive sensing platform, was constructed for the quantitative detection of D-amino acids in saliva. With the increase of D-amino acids concentration, the blue color of catalytic product gradually deepend, the fluorescence CDszymes gradually quenched, and the temperature gradually increased. Using D-alanine as D-amino acid models, the detection limits of D-alanine in colorimetric/photothermal/fluorescent mode were 0.3 μM, 1.8 μM, and 0.04 μM, respectively. The proposed detection platform exhibits promising application potential in clinical diagnostics. The exceptional sensing performance can be attributed to the utilization of CDszymes with outstanding POD activity. Revolving around the blind synthesis of CDszymes exhibiting high-efficiency POD activity, this study delved into the underlying mechanism governing the regulation of the POD activity of CDszymes by precursor functional groups. This work investigates the valence band theory to enhance the peroxidase-like of CDszymes, thereby offering a rational approach for designing CDszymes.

Fabrication of a novel reusable nanozyme by immobilizing Co-doped carbon dots on nanocellulose aerogels for efficient dyes degradation

Carbon dot-based nanozymes have gained significant attention, but their application in dye degradation remains limited due to low activity and challenges in recovery and reuse. To overcome these limitations, high peroxidase-active Co-doped carbon dots (CoCDs) with surface amines were synthesized via hydrothermal method and immobilized onto TEMPO-oxidized cellulose nanofibrils (TOCNF) aerogels using EDC/NHS coupling. For the first time, this study investigates the dye degradation efficiency of CDs nanozyme. CoCDs with 1.456 % Co content exhibited excellent peroxidase-like activity with favorable kinetics (Km = 1.746 mM, Vmax = 22.05 × 10-8 Ms-1 for TMB and Km = 1.542 mM, Vmax = 23.54 × 10-8 Ms-1 for H2O2). The immobilized CoCDs enhanced the structural stability, and shape recovery of aerogels, even after multiple compressions. CoCDs/TOCNF aerogel with maximum CoCDs (114.7 mg/g) exhibited superior degradation efficiency for various dyes, including methyl orange (MO), methylene blue (MB), and rhodamine B (RhB), with rate constants of 12.7 × 10-3, 17.4 × 10-3, and 12.2 × 10-3 min-1, respectively. Mechanistic studies revealed the major role of hydroxyl radicals in dye degradation. The aerogels exhibited exceptional recyclability with all dyes. This stable and recyclable nanozyme with high catalytic activity presents a promising avenue for environmental remediation.

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.

Optimizing peripheral blood chromosome analysis: effects of refrigeration time and blood volume

OBJECTIVE

This study aims to investigate the impact of refrigeration time and blood volume on the success rate of peripheral blood chromosomal analysis using response surface methodology (RSM).

METHODS

Peripheral blood samples from 30 volunteers were subjected to chromosomal analysis under different refrigeration duration periods (≤7 days, 8 days, 9 days, 10 days, 11 days, 12 days, 13 days, 14 days) along with different blood volumes (0.2 mL, 0.3 mL, 0.4 mL, 0.5 mL, 0.6 mL, 0.7 mL, and 0.8 mL). The effects of refrigeration time and blood volume on the success rate of peripheral blood chromosomal analysis were determined using the Chi-square test for trend, followed with Spearman's rank correlation coefficient, and RSM analysis to identify the optimal combination of refrigeration time and blood volume.

RESULTS

The refrigeration time within 10 days had a minor impact on the success rate, while refrigeration time more than 11 days significantly decreased the success rate. An increase in blood volume slightly improved the success rate. The success rate showed both linear and nonlinear changes with refrigeration time, while the effect of blood volume was primarily linear. The highest success rate was observed at a refrigeration time of ≤7 days and a blood volume of 0.8 mL. The interaction between refrigeration time and blood volume had a significant impact on the success rate.

CONCLUSION

It is recommended to keep the refrigeration time of blood samples within 7 days and control the blood volume at 0.8 mL to maximize the success rate of chromosomal analysis.

Enhanced Peroxidase-Mimic Catalytic Activity via Cerium Doping of Strontium-Based Metal-Organic Frameworks with Design of a Smartphone-Based Sensor for On-Site Salivary Total Antioxidant Capacity Detection in Lung Cancer Patients

The development of artificial nanozymes with superior catalytic performance and excellent stability has been a long-standing objective for chemists. The total antioxidant capacity (TAC) is one of the most important bioanalytical measures of oxidative stress in the body. The present work aims to develop a smartphone-assisted visual detection sensor using cerium-doped strontium-based metal-organic frameworks (Ce-SrMOFs) as peroxidase-like nanozymes for the rapid, low-cost, on-site detection of TAC. The pristine SrMOF functioned as a peroxidase nanozyme, and its enzymatic activity was enhanced after doping it with Ce(IV) ions because of the multivalent nature and synergistic impact of the heteroatoms. The Ce-SrMOFs were sensitive to the single electron transfer and hydrogen atom transfer processes, which implies that the Ce-SrMOFs can serve as an ideal nanozyme candidate for TAC analysis. The investigated mechanism revealed that •OH is the most active oxygen species for the peroxidase-like activity. The Ce-SrMOFs exhibited a strong affinity for 3,3',5,5'-tetramethylbenzidine (TMB) and H₂O₂, with K_m values of 0.082 and 0.427 mM, which are 5.29- and 8.67-fold lower than those of horseradish peroxidase (HRP), respectively. The Ce-SrMOFs were used for the detection of ascorbic acid, cysteine, and glutathione, with limits of detection of 44, 53, and 512 nM, respectively. The proposed method proved effective in measuring the TAC in saliva samples from lung cancer patients, thereby yielding results with satisfactory precision and accuracy.