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21. Atomically-precise Au24Ag1Clusterzymes with Enhanced Peroxidase-like Activity for Bioanalysis

Author

Wang, Shuna, Li, Zhe, Xia, Mingyuan, Zhao, Xiaoxue, Chen, Chuanxia, Jiang, Yuanyuan, Ni, Pengjuan, and Lu, Yizhong

Abstract

Atomically-precise clusterzymes have been widely studied for their special physicochemical properties, but it is still a challenge to enhance their peroxidase-like activity. Herein, we demonstrated that by substituting a single Ag atom into Au25nanoclusters to form Au24Ag1nanoclusters, the peroxidase-like activity was enhanced greatly. In the presence of H2O2, Au24Ag1could produce reactive oxygen species (ROS) to oxidize colorless 3,3’5,5’-tetramethylbenzidine (TMB) to the blue oxidized TMB (oxTMB). It is worth mentioning that pyrophosphate compounds inhibit the activity of Au24Ag1. Since alkaline phosphatase (ALP) can dephosphorylate the substrate phosphate compound, that is, remove the phosphate group on the substrate by hydrolysis, the enzymatic activity of the clusterzyme is restored. Based on this, we have developed a sensitive and reliable colorimetric sensing system for the detection of pyrophosphate ion (PPi), adenosine triphosphate (ATP), adenosine diphosphate (ADP) and ALP, respectively. Importantly, the detection limit of the assay system is lower than those of most of the assays that have been reported. In addition, we also built a simple optical logic gate on this basis, further extending the application of metal nanoclusters as peroxidase mimics in bioanalysis. This work could help to shed light on the structure-activity relationship of nanozyme.

Published
2023
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33. A Turn-On Fluorescent Assay for Glyphosate Determination Based on Polydopamine-Polyethyleneimine Copolymer via the Inner Filter Effect.

Author

Ni, Pengjuan, Liu, Siyuan, and Lu, Yizhong

Subjects
GLYPHOSATE, ALKALINE phosphatase, FLUORESCENCE quenching, FLUORESCENT probes, DETECTION limit, FOOD safety
Abstract

The threat of glyphosate to food safety has attracted widespread attention. Consequently, it is highly urgent to develop a sensitive and accurate method for glyphosate detection. Herein, a turn-on fluorescent method for glyphosate detection using polydopamine-polyethyleneimine (PDA-PEI) copolymer as a fluorescent probe and p-nitrophenylphosphate (PNPP)/alkaline phosphatase (ALP) as a fluorescence quenching system is developed. The PDA-PEI copolymer was prepared by a one-pot method under mild condition, and its fluorescence kept almost unchanged after storing in a refrigerator for one month. ALP catalyzed the hydrolysis of PNPP to p-nitrophenol (PNP) that caused the fluorescence quenching of PDA-PEI copolymer via the inner filter effect. However, glyphosate inhibited ALP activity, thereby preventing the formation of PNP and restoring the fluorescence signal. Under the optimized conditions, the fluorescence of PDA-PEI copolymer depended on glyphosate concentrations ranging from 0.2 to 10 μg/mL with a detection limit of 0.06 μg/mL. Moreover, this assay was applied to detect glyphosate in real samples using the standard addition method. The recoveries were in the range from 88.8% to 107.0% with RSD less than 7.78%. This study provides a novel insight for glyphosate detection and expands the applications of fluorescent copolymer. [ABSTRACT FROM AUTHOR]

Published
2023
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49. Spontaneous Deposition of Uniformly Distributed Ruthenium Nanoparticles on Graphitic Carbon Nitride for Quantifying Electrochemically Accumulated H2O2.

Author

Jiang, Yuanyuan, Ding, Zhenyu, Gao, Meng, Chen, Chuanxia, Ni, Pengjuan, Zhang, Chenghui, Wang, Bo, Duan, Guangbin, and Lu, Yizhong

Subjects
RUTHENIUM, OXIDATION-reduction reaction, ELECTROLYTIC reduction, NANOPARTICLES, NITRIDES, SURFACE cleaning, OXYGEN reduction
Abstract

Main observation and conclusion: Highly dispersed ultrasmall ruthenium nanoparticles with a clean surface are deposited onto graphitic carbon nitride (C3N4‐Ru) through spontaneous redox reaction between the C3N4 sheets and Ru salt without the use of any reductant. The as‐prepared C3N4‐Ru exhibits distinct peroxidase‐like activity. A nanozyme based method is successfully developed for detecting the H2O2 generated in‐situ by the two‐electron oxygen reduction strategy. The C3N4‐Ru nanozyme can realize the detection of H2O2 with a wide linear range and a low detection limit. The testing results are also compared with the conventional modified titration method, and show greater possibility for the practical detection of H2O2 produced via the electrochemical oxygen reduction for its higher selectivity. [ABSTRACT FROM AUTHOR]

Published
2021
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50. Colorimetric determination of the activity of acetylcholinesterase and its inhibitors by exploiting the iodide-catalyzed oxidation of 3,3′,5,5′-tetramethylbenzidine by hydrogen peroxide

Author

Li Zhuang, Yilin Wang, Shu Jiang, Zhen Li, Haichao Dai, Ni Pengjuan, Sun Yujing, and Wangdong Lu

Subjects
Detection limit, chemistry.chemical_classification, Chromatography, biology, 010401 analytical chemistry, Iodide, Substrate (chemistry), 02 engineering and technology, 3,3',5,5'-Tetramethylbenzidine, 021001 nanoscience & nanotechnology, 01 natural sciences, Acetylcholinesterase, Enzyme assay, 0104 chemical sciences, Analytical Chemistry, chemistry.chemical_compound, Thiocholine, chemistry, biology.protein, 0210 nano-technology, Hydrogen peroxide
Abstract

We describe a sensitive and selective colorimetric method for the determination of the activity of the enzyme acetylcholinesterase (AChE) and its inhibitors. Detection is based on the fact that acetylthiocholine iodide (ATCI) catalyzes the oxidation of the substrate 3,3′,5,5′-tetramethylbenzidine (TMB) by H2O2 to form a blue product (ox-TMB) with an absorption peak at 652 nm, but that oxidation is suppressed if ACTI previously is hydrolyzed by AChE to form thiocholine which decolorizes ox-TMB. In the presence of inhibitor, the activity of AChE is inhibited, thereby inducing the recovery of the blue coloration. Based on these findings, a highly sensitive method is developed for the determination of AChE and its inhibitors. The assay only requires mixing of buffer, solutions of ATCI, TMB, H2O2 and a sample containing AChE and photometric measurement. It works in the 0.05 to 5 mU•mL−1 enzyme activity range and has a detection limit as low as 30 μU•mL−1. The inhibitor neostigmine causes 50 % enzyme inhibition in 14.5 nM concentration. This analytical system has a wide scope in that it may be applied to the determination of the activity of various other hydrolases with proper substrates.

Published
2016

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