Synthesis of copper ion incorporated horseradish peroxidase-based hybrid nanoflowers for enhanced catalytic activity and stability†
In this study, we report the preparation, catalytic activity and stability of a hybrid nanoflower (hNF) formed from horseradish peroxidase (HRP) enzyme and copper ions (Cu2+). We studied the morphology of hNFs as a function of the concentrations of copper (Cu2+) ions, chloride ions (Cl−) and HRP enzyme, the pH of the buffer solution (phosphate buffered saline), and the temperature of the reaction. The effects of morphology on the catalytic activity and stability of hNFs were evaluated by oxidation of guaiacol (2-methoxyphenol) to colored 3,3-dimethoxy-4,4-diphenoquinone in the presence of hydrogen peroxide (H2O2). The enhanced activity of hNFs synthesized (from 0.02 mg mL−1 HRP in 10 mM PBS (pH 7.4) at +4 °C) was 17 595 U mg−1, which was ∼300% higher than free HRP in PBS, where it achieved an activity of 5952 U mg−1. In terms of stability, these hNFs stored in PBS buffer at +4 °C and room temperature (RT = 20 °C) lost 4% and 20%, respectively, of their initial catalytic activities within 30 days. Finally, we demonstrated that these hNFs can be utilized as sensors for the detection of dopamine.