Influence of Surface Modification on Iron Oxide Peroxidase-Mimic Activity for Antibacterial Application

Concerns over microbial drug resistance drive extensive research for effective, stable, and broadspectrum antimicrobial agents. Iron oxide nanoparticles (IONPs) have emerged as promising candidates owing to their intrinsic catalytic, magnetic properties, and biocompatibility [1]. These IONPs exhibit peroxidase (POD)-like activity, enabling the generation of reactive oxygen species (ROS) with potent antibacterial effects [2]. However, immediate radical quenching due to ultra-short halftime hampers diffusion and bactericidal efficacy. [3]. Our study aimed to investigate the POD-like activity of diverse IONP formulations and evaluate the impact of surface modification on their catalytic activity and antibacterial efficiency. Commercial NPs employed in our investigation included superparamagnetic iron oxide NPs (SPIONs), palladium-coated SPIONs (SPION-Pd), and  polymercoated γ-Fe2O3 NPs. Additionally, we have synthesized Fe3O4 NPs coated with oleic acid (OA-Fe3O4). 
Characterization of these IONPs was conducted using TEM, EDS, FTIR, and DLS techniques. Evaluation of POD-like activity and leached ions employed the TMB-H2O2 and ABTS-H2O2 assays, with absorbance measurements conducted at 650 nm and 405 nm, respectively. Notably, aptamer adsorption onto NPs induced significant alterations in the zeta potential of IONPs, corroborated by the presence of a phosphate peak in the FTIR spectra. Our preliminary findings unveiled distinctive responses to aptamer adsorption across various IONP formulations. Substrate-specific catalytic activity was observed, with OA-Fe3O4 and SPIONs exhibiting a notable increase in POD-like activity in the TMB-H2O2 assay upon aptamer adsorption. Conversely, in SPION-Pd and polymer-coated γ-Fe2O3, catalytic activity diminished in the TMB reaction following aptamer adsorption. In the ABTS-H2O2 assay, a decrease in POD-like activity was observed in OA-Fe3O4 and SPIONs upon aptamer adsorption. Our preliminary data indicate successful aptamer functionalization, and enhanced POD-like activity post-adsorption, suggesting potential for improved antibacterial efficacy. Future endeavors will focus on the identification of specific aptamers, antibodies, and nanobodies targeting pathogenic bacteria, alongside investigations into the capture and antibacterial activity of these nanoparticle formulations. 

1. Asma Ghazzy, et al., Magnetic iron oxide-based nanozymes: from synthesis to application. Nanoscale 
Advances, 2024/03/12. 6(6).
2. Sang, Y., et al., Construction of Nanozyme‐Hydrogel for Enhanced Capture and Elimination of Bacteria.
Advanced Functional Materials, 2019/05/01. 29(22).
3. Gao, L., et al., Intrinsic peroxidase-like activity of ferromagnetic nanoparticles. Nature Nanotechnology 
2007 2:9, 2007-08-26. 2(9).