# Efficient Oxidative Polymerization of Hydroxytyrosol Using Horseradish Peroxidase Immobilized on a Magnetic Silica‐Coated Nanocatalyst

## TL;DR

Scientists created a reusable magnetic nanocatalyst to efficiently polymerize hydroxytyrosol using an enzyme, offering a sustainable and cost-effective method for green chemistry.

## Contribution

A novel magnetic nanocatalyst for horseradish peroxidase immobilization is developed, enabling efficient and reusable oxidative polymerization of hydroxytyrosol.

## Key findings

- The nanocatalyst is reusable for up to ten cycles with a 73% polymerization yield.
- The produced poly(hydroxytyrosol) has a molecular weight of approximately 30,000 g mol−1.
- Characterization techniques confirmed successful immobilization and stability of the enzyme on the nanocatalyst.

## Abstract

Enzyme‐based catalysis has gained considerable attention in recent years due to its eco‐friendly and selective nature. However, the inability to recover enzymes after the reaction significantly increases operational costs. In this study, a reusable nanocatalyst Fe3O4@SiO2@APTES@GA@HRP is synthesized and applied in the oxidative polymerization of hydroxytyrosol. Fe3O4 nanoparticles are prepared using the solvothermal method, followed by silica coating via the Stöber process. Amino‐functionalization is achieved with 3‐aminopropyltriethoxysilane (APTES), and horseradish peroxidase (HRP) is immobilized through glutaraldehyde (GA)‐mediated azomethine bonding. The synthesized catalyst is characterized using SEM, EDS, FTIR, Q‐TOF, ¹H‐NMR, and Zetasizer analyses, all confirming successful immobilization. Polymerization reactions are conducted in acetate buffer (pH 5, 25 °C), resulting in a 73% yield. The catalyst is reusable for up to ten cycles, and the molecular weight of the produced poly(hydroxytyrosol) is approximately 30,000 g mol−1. These findings demonstrate the promising application of recyclable enzyme nanocatalysts in green polymer chemistry.

A magnetic Fe₃O₄@SiO₂@APTES@GA nanocatalyst is synthesized for horseradish peroxidase (HRP) immobilization, enabling efficient oxidative polymerization of hydroxytyrosol under mild conditions. The biocatalyst demonstrates high thermal and pH stability, strong reusability over 10 cycles, and effective polymerization performance. Characterizations including SEM, EDS, FTIR, TGA, and kinetic analyses confirmed successful catalyst fabrication and enhanced enzymatic functionality. This work contributes to sustainable green catalysis and nanobiotechnology applications.