Polymer-capped iron oxide nanoparticles: Influence on physicochemical properties and antibacterial efficacy

Iron oxide nanoparticles (IONP) are versatile materials that exhibit antibacterial properties through membrane damage and ROS production. However, the agglomeration tendency and poor colloidal dispersion in the aqueous medium limit their application. In this study, polymer-capped IONP were developed using three different polymers: polyethylene glycol (PEG 4000), polyvinyl pyrrolidone (PVP K-30), and hydroxypropyl methyl cellulose (HPMC E15) at three different concentrations (0.1%, 0.5%, and 1.0%) to prevent agglomeration and enhance IONP colloidal stability. The successful formation of the polymer-capped IONP was indicated by the hydrogen bond observed from the FT-IR spectrum, interference of the polymer in the crystal lattice of IONP, the smooth surface with an allegedly sheet-like structure, and less agglomerated particles. The application of a capping layer significantly reduced the hydrodynamic particle size of IONP from 140.00±27.90 nm to 82.20±10.14, 68.79±11.50, and 70.07±6.99 nm for IONP capped by PEG 1.0%, PVP 0.1%, and HPMC 1.0%, respectively. The disk diffusion antibacterial assay revealed a higher inhibition zone of the polymer-capped IONP than bare IONP towards Escherichia coli and Staphylococcus aureus . However, the minimum inhibitory concentration (MIC) determination using the microbroth dilution test possessed limitations in inhibiting bacterial growth due to insufficient direct contact of polymer-capped IONP with the bacterial membrane. The promising polymer-capped IONP systems for further development were IONP-PEG 1.0%, IONP-PVP 0.1%, and IONP-HPMC 1.0%, as depicted through Principal Component Analysis (PCA). The radical scavenging activity presented by polymer-capped IONP enhances its feasibility as an antibacterial agent for infectious diseases and antioxidant properties in the biomedical field.