Hydroxyl Radical Generation through the Fenton-like Reaction of Hematin- and Catechol-Functionalized Microgels

Abstract

Hydroxyl radical (^•OH) is a potent reactive oxygen species with the ability to degrade hazardous organic compounds, kill bacteria, and inactivate viruses. However, an off-the-shelf, portable, and easily activated biomaterial for generating ^•OH does not exist. Here, microgels were functionalized with catechol, an adhesive moiety found in mussel adhesive proteins, and hematin (HEM), a hydroxylated Fe³⁺ ion-containing porphyrin derivative. When the microgel was hydrated in an aqueous solution with physiological pH, molecular oxygen in the solution oxidized catechol to generate H₂O₂, which was further converted to ^•OH by HEM. The generated ^•OH was able to degrade organic dyes, including orange II and malachite green. Additionally, the generated ^•OH was antimicrobial against both gram-negative (<i>Escherichia coli</i>) and gram-positive (<i>Staphylococcus epidermidis</i>) bacteria with the initial concentration of 10⁶-10⁷ CFU/mL. These microgels also reduced the infectivity of a non-enveloped porcine parvovirus and an enveloped bovine viral diarrhea virus by 3.5 and 4.5 log reduction values, respectively (99.97-99.997% reduction in infectivity). These microgels were also functionalized with positively charged [2-(methacryloyloxy)ethyl] trimethylammonium chloride (METAC), which significantly enhanced the antibacterial and antiviral activities through electrostatic interaction between the negatively charged pathogens and the microgel. These microgels can potentially serve as a lightweight and portable source of disinfectant, for an on-demand generation of ^•OH with a wide range of applications.