Enhanced His@AuNCs oxidase-like activity by reduced graphene oxide and its application for colorimetric and electrochemical detection of nitrite

Abstract

Enzyme-mimicking (nanozyme)-based biosensors are attractive owing to their unique catalytic efficiency, multifunctionality, and tunable activity, but examples of oxidase-like nanozymes are quite rare. Herein, we demonstrated that histidine-capped gold nanoclusters (His@AuNCs) possessed intrinsic oxidase-like activity, which could directly oxidize 3,3′,5,5′-tetramethylbenzidine (TMB) to blue colored ox-TMB without H 2 O 2. The assembly of reduced graphene oxide (RGO) with His@AuNCs could further improve its oxidase-like activity and the His@AuNCs/RGO nanocomposites had a lower Michaelis constant (K m) and higher catalytic constant (K cat) for TMB oxidation. Furthermore, compared to other nanomaterials, the as-prepared His@AuNCs/RGO also exhibited enhanced electrocatalytic activity toward TMB. Interestingly, nitrite inhibited the catalytic (chromogenic) and electrocatalytic processes of His@AuNCs/RGO in the oxidation of TMB. The oxidase-like and electrocatalytic activity of His@AuNCs/RGO was evaluated with nitrite and TMB as substrates, and the results indicated that TMB and nitrite might share the same catalytic active sites. On the basis of these findings, a colorimetric and electrochemical sensor was developed with the His@AuNCs/RGO composite as an oxidase mimic for determination of nitrite with linear ranges of 10-500 μM and 2.5-5700 μM, respectively. The developed method was successfully applied to the detection of nitrites in real samples. The present work suggests that the oxidase-like nanozyme is not only suitable for colorimetric assay but also for development of electrochemical sensors in bioanalysis.

Synthesis, Catalytic Properties and Application in Biosensorics of Nanozymes and Electronanocatalysts: A Review

“…Furthermore, PtNPs exhibited catalase-and PO-like activities. In another example, oxidase-like nanosheets were prepared [41] using the chemical reduction method modified by Hummers et al [42], in which histidine enantiomers served as both a reducing agent and a protecting ligand. Compared to the previously developed strategies, this synthesis method is very rapid and mild and does not require heating, pressuring, and special media.…”

“…The oxidase-like and electrocatalytic activity of His@AuNCs/RGO was evaluated for the determination of nitrite ( Table 3). The developed method was used for the detection of nitrites in real samples [41].…”

“…It was assumed that His@AuNCs react via enzyme-like catalytic centers, when substrates and active sites of His@AuNCs are located on the RGO sheets. The "co-interaction" between the His@AuNCs and RGO increases the speed of electron transfer from TMB to oxygen, leading to enhanced catalytic activity [41]. In another example, the catalytic steady-state kinetics for CoFe2O4 CF300 was estimated using TMB and H2O2 as substrates [71].…”

Development of Nanozymes for Food Quality and Safety Detection: Principles and Recent Applications

“…Additionally, Liu et al. () developed a colorimetric/electrochemical dual‐mode sensor for nitrite detection using the nanohybrid of rGO and histidine‐capped gold nanoclusters (His@Au NCs/rGO) with intrinsic OXD‐like activity. The colorimetric/electrochemical sensor was performed on the principle that nitrite could inhibit the catalytic (chromogenic) and electrocatalytic processes of His@AuNCs/RGO in the oxidation of TMB, which could respond to nitrite in the linear ranges of 10‐500 µM and 2.5‐5700 µM, respectively.…”

A novel nanozyme based on selenopeptide-modified gold nanoparticles with a tunable glutathione peroxidase activity

“…[21][22][23][24] The tailored surface functionalization of gold nanoparticles controls the interface between AuNPs and biomolecules, [25][26][27] and it is crucial for development and design of tunable catalytic activities. [28][29][30] Glutathione peroxidase (GPx) is an important selenoenzyme in the cellular antioxidant defense system, which protects cells from oxidative damage by catalyzing the degradation of a variety of hydroperoxides (ROOH) using glutathione (GSH) as the reductant. [31][32][33][34][35] GPx contains an essential selenocysteine (Sec) residue at its active site, [36][37][38] and this residue has clear catalytic characteristics.…”