Ultra-Thin 2D CuO Nanosheet for HRP Immobilization Supported by Encapsulation in a Polymer Matrix: Characterization and Dye Degradation

Abstract

Herein, we report the immobilization of horseradish peroxidase (HRP) on a novel two-dimensional copper oxide nanosheet (CuONS) and supported by encapsulation in poly (methyl methacrylate) (PMMA). The morphological/chemical properties of the immobilized HRP on CuONS-PMMA were investigated and characterized by scanning electron microscopy, and Fourier transforms infrared spectroscopy. After optimizing the immobilization conditions, recovered HRP activity was 72.8% using 1% CuONS–PMMA. Reusing the immobilized enzyme for ten cycles indicated that 52% of its initial activity was retained. Moreover, the immobilization of HRP using this method led to a shift in its optimum pH from 7 to broad optimum 7–7.5 and optimum temperature from 40 °C to broad optimum 40–50 °C. Km values of free and immobilized HRP were 30 and 46.7 mM for guaiacol and 5.53 and 8.55 mM for H2O2, respectively. The immobilized HRP enzyme was more stable towards metal ions. The immobilized HRP was used for crystal violet, methyl green, and malachite green dyes degradation. The immobilized HRP showed significant improvement in the capacity for dye decolorization relative to free enzyme. Therefore, based on all the characteristics mentioned above, it may be suggested that the use of this technique for HRP immobilization appears to be promising for industrial applications. A schematic illustration of the immobilization process of HRP on CuONS/PMMA.