A Highly Efficient Nano-Cluster Artificial Peroxidase and Its Direct Electrochemistry on a Nano Complex Modified Glassy Carbon Electrode

Abstract

A nano-cluster with highly efficient peroxide activity was constructed based on nafion (NF) and cytochrome c (Cyt c). UV-Vis spectrometry and transmission electron microscopy (TEM) methods were utilized for characterization of the nano-structured enzyme or artificial peroxidase (AP). The nano-cluster was composed of a Chain-Ball structure, with an average ball size of about 40 nm. The Michaelis–Menten (K_m) and catalytic rate (k_cat) constants of the AP were determined to be 2.5 ± 0.4 μM and 0.069 ± 0.001 s⁻¹, respectively, in 50 mM PBS at pH 7.0. The catalytic efficiency of the AP was evaluated to be 0.028 ± 0.005 μM⁻¹ s⁻¹, which was 39 ± 5% as efficient as the native horseradish peroxidase (HRP). The AP was also immobilized on a functional multi-wall carbon nanotube (MWNCTs)-gold colloid nanoparticles (AuNPs) nano-complex modified glassy carbon (GC) electrode. The cyclic voltammetry of AP on the nano complex modified GC electrode showed a pair of well-defined redox peaks with a formal potential (E°′) of –45 ± 2 mV (vs. Ag/AgCl) at a scan rate of 0.05 V/s. The heterogeneous electron transfer rate constant (k_s) was evaluated to be 0.65 s⁻¹. The surface concentration of electroactive AP on GC electrode (Γ) was 7 × 10⁻¹⁰ mol cm⁻². The apparent Michaelis–Menten constant (K_m^app) was 0.23 nM.