Elsevier

Process Biochemistry

Volume 95, August 2020, Pages 131-138
Process Biochemistry

Core-shell Au@Co-Fe hybrid nanoparticles as peroxidase mimetic nanozyme for antibacterial application

https://doi.org/10.1016/j.procbio.2020.05.003Get rights and content

Highlights

Abstract

Nanozymes have been developed as alternative for enzymes to overcome practical limitations of enzymes in industry and medicine. Infectious diseases are becoming severe threat to public health. Hence, peroxidase nanozyme for combating bacteria have been designed. Core-Shell Au@Co-Fe hybrid nanoparticles (Au@Co-Fe NPs) were synthesized. The structure of Au@Co-Fe NPs was characterized by UV–vis and FT-IR spectroscopic methods. The size, zeta potential and spherical morphology of Au@Co-Fe NPs were determined by DLS, TEM and AFM techniques. Au@Co-Fe NPs has been evaluated as peroxidase mimic nanozyme. The peroxidase mimetic activity of gold nanoparticles, Co (II) and Fe (III) were measured and compared with that obtained for native HRP. The enzymatic measured activity was 50% of native horse radish peroxidase. Additionally, Au@Co-Fe NPs was evaluated as antibacterial agent against four selected standard pathogenic bacteria as Escherichia coli, Pseudomonas aeruginosa (as gram negative) and Staphylococcus aureus, and Bacillus cereus (as gram positive).

Introduction

Enzymes are natural catalysts which accelerate the biochemical reactions up to 1019 times with high specificity [1]. They are essential to all vital biological processes such as metabolism, growth, DNA replication and transcription, protein synthesis, blood coagulation, and many other biological activities [2]. Because of their high catalytic activity and specificity, enzymes have been used in a variety of industries such as pharmaceuticals, feed industry, chemical production, cosmetic products, biofuels, food processing, and others [2]. Although enzymes exhibit a lot of advantages, they present several limitations in operational usage. These limitations are high cost, low stability in environment changes (such as pH and temperature) and storage [3]. Consequently, artificial enzymes which mimic the catalytic activity of natural enzymes were developed.

Artificial enzymes are more stable and inexpensive than natural enzymes. By emerging of nanotechnology with biology next generation of artificial enzymes introduced as nanozymes [4]. Nanozyme defined as a functional nanomaterial that mimics the catalytic activity of natural enzyme. Up to now, a lot of nanomaterials that mimic the catalytic activity of enzymes, for extensive applications, have been developed. Several reviews reported structure and function of developed nanozymes [[5], [6], [7], [8]]. For example, Fe3O4 nanoparticles, cobalt nanoparticles, graphene oxide (GO) nanosheets, silver nanoparticles, copper nanoparticles and etc. have been shown to possess a peroxidase mimetic activity. Additionally, gold nanoparticls (AuNPs) show excellent peroxidase [9] or superoxide dismutase mimetic activity [10] depending on functional groups. Nanozymes possess wide variety applications such as in biosensors [11], therapeutic agents [12], environmental treatment [13], cryopreservation (use in assisted reproductive treatment) [14,15], cytoprotection in the cell [16], imaging, cancer treatment [17] and wound healing [18]. Besides, nanozymes have also showed appropriate antibacterial activity [5]. Due to the peroxidase mimetic activity of iron, cobalt and gold metals, we thought that the Au@Co-Fe NPs hybrid might enhance their individual peroxidase mimetic activity.

Infectious bacteria are one of the most important health challenges around the world. Up to now, a lot of drugs were discovered to kill bacteria, such as antibiotics, metal and ammonium ion [19]. However, it is a concern that these materials cause antibiotic resistance, pollution, high cost and harsh synthesis process [20]. Recently, scientists reported that nanozymes with peroxidase or oxidative mimetic activity could catalyze decomposition of H2O2 to produce high activity OH, and kill bacteria efficiently. It was reported that AuNPs supported mesoporous silica, possess dual enzyme activities as peroxidase and oxidase mimic and also antibacterial activity [21]. Incorporation of AuNPs with ultrathin graphitic carbon nitride provides peroxidase nanozyme for bacterial killing [22,23]. Hence, we selected AuNPs and modified it for better antibacterial activity.

In this paper, AuNPs were synthesized and functionalized by iron and cobalt ions (Au@Co-Fe NPs). The structural analysis of Au@Co-Fe NPs was done by UV–vis and FT-IR spectroscopy. The peroxides mimetic activity of Au@Co-Fe NPs was assessed. The obtained nanozyme demonstrated antibacterial activity against four selected standard pathogenic bacteria as Escherichia coli, Pseudomonas aeruginosa (as gram negative) and Staphylococcus aureus, and Bacillus cereus.

Section snippets

Materials

HAuCl4, Trisodiumcitratedihydrate (Na3C6H5O7.2H2O), CoCl2.6H2O, FeSO4.7H2O, Tween-20, 4- aminoantipyrine (4-AAP), phenol, hydrogen peroxide 30% (H2O2), trypic soy agar (TSA) and trypic soy broth (TSB) were purchased from Merck (Germany). Tetracycline (TE), ampicillin (AM), medium and 4-aminoantipyrine (4-AAP) were obtained from Sigma.

Apparatus

UV-Vis absorption spectra of the synthesized nanoparticles were measured at room temperature with a Varian Cary Bio 100 spectrophotometer. The particles were

Spectroscopic studies

For synthesis of Au@Co-Fe NPs, first AuNPs were prepared and then cobalt and iron cations attached on their surface with electrostatic interactions. To confirm AuNPs formation and following that Au@Co-Fe NPs formation UV–vis spectroscopy was used. As seen in Fig. 1, an absorption maximum at 530 nm revealed that Au NPs were formed successfully. After incubation of AuNPs with CoCl2 and FeSO4 salts and Au@Co-Fe NPs formation, the surface plasmon resonance (SPR) absorption of AuNPs show

Conclusion

The results demonstrated that Au@Co-Fe NPs nanozyme possess peroxidase mimic activity. The combination of AuNPs with cobalt and iron salts elevated the peroxidase mimetic activity of AuNPs in decomposing H2O2. Au@Co-Fe NPs nanozyme exhibited antibacterial activity against E. coli, P. aeruginosa and S. aureus, and B. cereus. Au@Co-Fe NPs nanozyme may use in place of natural enzymes due to its easy preparation, robustness, and stability against environmental changes.

Author statement

Conceptualization: Fariba Dashtestani, Fatemeh Hakimian

Data curation: Alireza Shekari-Far, Fatemeh Hakimian, Mahboubeh Mirhosseini

Formal analysis: Alireza Shekari-Far, Fariba Dashtestani, Fatemeh Hakimian, Mahboubeh Mirhosseini

Funding acquisition: Fatemeh Haghiralsadat, Seyed Kamal Fatemi.

Investigation: Alireza Shekari-Far, Seyed Kamal Fatemi

Methodology: Alireza Shekari-Far, Fariba Dashtestani, Fatemeh Hakimian, Mahboubeh Mirhosseini, Fatemeh Haghiralsadat.

Project administration: Fariba

Declaration of Competing Interest

Authors have no received research grants. The authors declare that they have no conflict of interest.

Acknowledgments

The financial support of Payam e Noor university of Taft branch is greatly acknowledged. Also authors gratefully acknowledge the generous cooperation of the Nano Structured Coatings Institute, Yazd Payame Noor University, Yazd, Iran.

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