Elsevier

Analytica Chimica Acta

Volume 1128, 1 September 2020, Pages 72-79
Analytica Chimica Acta

Peroxidase-like activity of Fe–N–C single-atom nanozyme based colorimetric detection of galactose

https://doi.org/10.1016/j.aca.2020.06.027Get rights and content

Highlights

  • The Fe-SAzyme was synthesized by low-cost precursors and simple procedure.

  • The Fe-SAzyme displayed high stability and excellent peroxidase-like activity.

  • A convenient and economic colorimetric detection method for H2O2 and galactose has been successfully established.

  • This proposed strategy exhibited satisfactory performance for galactose assay in human serum samples.

Abstract

Single atom nanozymes are the artificial enzymes with enzyme-like activity, which have attracted a great deal attention in recent years due to their unique merits such as remarkable stability, excellent atom utilization and low cost. Herein, a convenient and sensitive colorimetric strategy was developed for the sensing of galactose based on Fe–N–C single-atom nanozyme (Fe-SAzyme). The Fe-SAzyme was prepared through “isolation-pyrolysis” method that exhibited intrinsic peroxidase mimicking activity, which can quickly catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) to produce blue-colored oxTMB in the presence of hydrogen peroxide (H2O2). Galactose can be oxidized by galactose oxidase (Gal Ox) to generate H2O2, and Fe-SAzyme can be utilized for quantitative colorimetric detection of galactose. A good linearity between absorbance and the galactose concentration in the range of 50–500 μM was obtained with a detection limit of (LOD) 10 μM. The Fe-SAzyme based colorimetric strategy offered a rapid, convenient and economic way for galactose quantification detection, which could be used as an alternative method for galactosemia diagnosis.

Introduction

Galactosemia is a toxic clinical metabolic syndrome with higher blood galactose because of the decrease of metabolism of galactose, which is regarded as one of the major metabolic diseases of newborn babies [1,2]. High galactose content in the body may lead to fatal galactosemia, which is accompanied with cirrhosis, liver failure, growth retardation, mental retardation, hypoglycemia, cataract and many other complications [3]. Newborns who are not correctly diagnosed and treated in the early stage will endanger the life in the neonatal period [[3], [4], [5]]. The diagnosis of galactosemia is generally accomplished by the methods of dried blood spot specimens [2], high performance liquid chromatography [6] and laser-induced fluorescence [7]. However, these techniques usually required highly specialized instruments and intricate sample processing [8]. Therefore, developing a simple, economical and sensitive assay for clinical diagnosis of galactosemia is highly required.

In recent years, many nanomaterials with enzyme-like activities have been increasingly studied [[9], [10], [11], [12], [13], [14]]. These nanomaterials, called nanozymes, hold generous virtues such as low cost, high selectivity, outstanding resistance to extreme conditions including high temperature, acid-alkali and organic solvent compared with natural enzymes. Up to now, a variety of nanomaterials with enzyme-like activities have been explored including various transition metal oxide-based materials [15], metal sulfide nanoparticles [16], noble metal nanoparticles and nanoclusters [17,18], carbon-based nanostructures [19], and metal-organic frameworks [20]. Among them, single atom nanozymes (SANs) with isolated metal atoms dispersed on supports have drawn great attention [21]. SANs have uniformly dispersed active sites without notable interactions with each other, which greatly improves the efficiency of atom utilization and the density of active sites, thus significantly improves the catalytic performance [22,23]. In addition, the isolated metal atoms are firmly anchored into the skeleton of the supports, and the strong metal-supports interactions make SANs have superior stability [24]. Thus, those intrinsic drawbacks of nanozymes such as low activity can be largely avoided. Therefore, SANs are regarded as ideal nanozymes due to the favorable activity [25]. SANs have been widely studied in photocatalysis, electrocatalysis and thermalcatalysis [26]. However, there are few reports about the peroxidase activity and application of SANs.

In the present work, we found that the Fe–N–C single-atom nanozyme (Fe-SAzyme) exhibited impressive peroxidase-like activity. There will generate hydrogen peroxide (H2O2) during the process of catalytic oxidation of galactose by galactose oxidase (Gal Ox), Fe-SAzyme can catalyze H2O2 to produce hydroxyl radical (⸱OH), and further catalyze the oxidation of TMB to produce blue-colored oxTMB (Scheme 1). The peroxidase-like activity of the nanozyme was greatly determined by pH, temperature and concentration of H2O2, and exhibited extremely high affinity for H2O2. Therefore, Fe-SAzyme can be employed as peroxidase mimetic to developed a simple and rapid colorimetric assay for galactose detection.

Section snippets

Materials and instruments

Zn(NO3)2·6H2O was obtained from Guangfu Reagent Co., Fe(acac)3 was purchased from RHAWN Chemical Co., Ltd. 2-Methyimidazole, galactose oxidase (Gal Ox), 3,3′,5,5′-tetramethylbenzidine (TMB) and N-Ethylmaleimide (NEM) were purchase from Aladdin Reagent Co., Ltd. Galactose, glycine, proline, threonine, glutathione, cysteine were purchase from Beijing Dingguo Biotechnology Co., Ltd. Hydrogen peroxide (H2O2), N,N-dimethylformamide (DMF), sodium acetate (NaAc), acetic acid (HAc) and Methanol were

Characterization of Fe-SAzyme

The sizes and morphologies of the prepared Fe-SAzyme were investigated by transmission electron microscope (TEM). Fig. 1B revealed that the obtained Fe-SAzyme maintained the dodecahedral structure well after pyrolysis from Fe(acac)3@ZIF-8 NPs, and displayed average size of around 150 nm. In comparison with ZIF-8 sample without inserted precursor, the position of the diffraction peak of Fe(acac)3@ZIF-8 shifted slightly (Fig. 1C), which illustrated the successful import of the precursor molecules

Conclusions

In summary, the single-atom Fe nano-enzyme (Fe-SAzyme) were successfully synthesized and possessing excellent peroxidase-mimicking activity, which can effectively catalyze the oxidation of TMB after combined with H2O2, so it can be used for quantitative colorimetric detection of galactose in the presence of Gal Ox. The Fe-SAzyme based colorimetric strategy exhibited high sensitivity and good selectivity for the galactose analysis and was successfully used for the galactose determination in

CRediT authorship contribution statement

Xiaobin Zhou: Conceptualization, Validation, Investigation, Formal analysis, Writing - original draft. Mengke Wang: Investigation, Data curation, Writing - review & editing. Junyang Chen: Formal analysis, Software. Xiaolei Xie: Resources. Xingguang Su: Methodology, Supervision, Funding acquisition, Project administration.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

This work is supported by the National Natural Science Foundation of China (No. 21775052 and No. 21575048), the Science and Technology Development project of Jilin province, China (No. 20180414013GH).

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