Phytosynthesis of Palladium Nanoclusters: An Efficient Nanozyme for Ultrasensitive and Selective Detection of Reactive Oxygen Species.

Ravi Mani Tripathi,Sang J Chung

doi:10.3390/molecules25153349

Ravi Mani Tripathi, Sang J Chung

Open Access

https://doi.org/10.3390/molecules25153349

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Abstract

Hydrogen peroxide is a low-reactivity reactive oxygen species (ROS); however, it can easily penetrate cell membranes and produce highly reactive hydroxyl radical species through Fenton’s reaction. Its presence in abnormal amounts can lead to serious diseases in humans. Although the development of a simple, ultrasensitive, and selective method for H2O2 detection is crucial, this remains a strategic challenge. The peroxidase mimetic activity of palladium nanoclusters (PdNCs) has not previously been evaluated. In this study, we developed an ultrasensitive and selective colorimetric detection method for H2O2 using PdNCs. An unprecedented eco-friendly, cost-effective, and facile biological method was developed for the synthesis of PdNCs. This is the first report of the biosynthesis of PdNCs. The synthesized nanoclusters had a significantly narrow size distribution profile and high stability. The nanoclusters were demonstrated to possess a peroxidase mimetic activity that could oxidize peroxidase substrate 3,3′,5,5′-tetramethylbenzidine (TMB). Various interfering substances in serum (100 μM phenylalanine, cysteine, tryptophan, arginine, glucose, urea, Na+, Fe2+, PO43−, Mn+2, Ca2+, Mg2+, Zn2+, NH4+, and K+) were included to evaluate the selectivity of the assay, and oxidation of TMB occurred only in the presence of H2O2. Therefore, PdNCs show an efficient nanozyme for the peroxidase mimetic activity. The assay produced a sufficient signal at the ultralow concentration of 0.0625 µM H2O2. This colorimetric assay provides a real-time, rapid, and easy-to-use platform for the detection of H2O2 for clinical purposes.

Highlights

Enzymes are frequently used to catalyze the conversion of biomolecules; they require mild conditions to facilitate the reaction
The biosynthesis of palladium nanoclusters (PdNCs) was determined by measuring their absorbance as a function of time after the addition of leaf extract to the palladium chloride solution
This peak almost disappeared after the synthesis of the nanocluster (Figure 1b) and the amount of PdNC was estimated based on the amount of the used PdCl2

Summary

Introduction

Enzymes are frequently used to catalyze the conversion of biomolecules; they require mild conditions to facilitate the reaction. Chemical catalysts can facilitate reactions under harsh conditions, such as high pressures, high temperatures, organic solvents, and extreme pH [1,2]. Enzymes have some inherent limitations, such as high preparation and purification costs, low operational stability, sensitivity to environmental conditions, and difficulties in recycling and reuse [3]. To overcome these limitations, researchers are exploring the possibility of developing artificial enzyme mimics that are cost-effective and have high stability. Several studies have explored the development of artificial enzyme ( called nanozyme [3]) mimic materials, such as ZnO-Pd nanosheets [4], Fe3O4 nanoparticles [5], Cu–Ag on graphene oxide [6], and metal–organic

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