Influence of Physicochemical Properties of Iron Oxide Nanoparticles on Their Antibacterial Activity

Abstract

The increasing occurrence of infectious diseases caused by antimicrobial resistance organisms urged the necessity to develop more potent, selective, and safe antimicrobial agents. The unique magnetic and tunable properties of iron oxide nanoparticles (IONPs) make them a promising candidate for different theragnostic applications, including antimicrobial agents. Though IONPs act as a nonspecific antimicrobial agent, their antimicrobial activities are directly or indirectly linked with their synthesis methods, synthesizing precursors, size, shapes, concentration, and surface modifications. Alteration of these parameters could accelerate or decelerate the production of reactive oxygen species (ROS). An increase in ROS role production disrupts bacterial cell walls, cell membranes, alters major biomolecules (e.g., lipids, proteins, nucleic acids), and affects metabolic processes (e.g., Krebs cycle, fatty acid synthesis, ATP synthesis, glycolysis, and mitophagy). In this review, we will investigate the antibacterial activity of bare and surface-modified IONPs and the influence of physiochemical parameters on their antibacterial activity. Additionally, we will report the potential mechanism of IONPs' action in driving this antimicrobial activity.

Figure 1

Schematic representation of (a) hematite, (b) maghemite, (c) magnetite, (d) lepidocrocite, and (e) goethite structures. These structures are viewed from the ⟨001⟩ or ⟨0001⟩ directions. The idea of the diagram is taken from Guo and Barnard.

Figure 2

An illustration of the numerous IONPs parameters that influenced the antibacterial activity. Here, AA: antimicrobial activity, AN: agar nutrient, AMH: agar Mueller-Hinton solution, LB: lysogenic broth, Amx: amoxicillin, TB: tryptic-soy broth, APD: agar potato dextrose solution, BN: broth of nutrient, BS: bacteriostatic effect, BC: bactericidal effect, and BG: bacterial growth.

Figure 3

A diagrammatic illustration of IONPs antibacterial and antibiofilm mechanisms. IONPs trigger oxidative stress and cell lysis by generating ROS, altering membrane depolarization, damaging protein or nucleic acid, inactivating enzymes, damaging mitochondria or ribosome, impairing efflux pump, disrupting cytoplasm and cell membrane. ROS: Reactive oxygen species; IONPs: Iron oxide nanoparticles.