Antimicrobial activity of iron oxide nanoparticle upon modulation of nanoparticle-bacteria interface

Abstract

Investigating the interaction patterns at nano-bio interface is a key challenge for safe use of nanoparticles (NPs) to any biological system. The study intends to explore the role of interaction pattern at the iron oxide nanoparticle (IONP)-bacteria interface affecting antimicrobial propensity of IONP. To this end, IONP with magnetite like atomic arrangement and negative surface potential (n-IONP) was synthesized by co-precipitation method. Positively charged chitosan molecule coating was used to reverse the surface potential of n-IONP, i.e. positive surface potential IONP (p-IONP). The comparative data from fourier transform infrared spectroscope, XRD, and zeta potential analyzer indicated the successful coating of IONP surface with chitosan molecule. Additionally, the nanocrystals obtained were found to have spherical size with 10–20 nm diameter. The BacLight fluorescence assay, bacterial growth kinetic and colony forming unit studies indicated that n-IONP (<50 μM) has insignificant antimicrobial activity against Bacillus subtilis and Escherichia coli. However, coating with chitosan molecule resulted significant increase in antimicrobial propensity of IONP. Additionally, the assay to study reactive oxygen species (ROS) indicated relatively higher ROS production upon p-IONP treatment of the bacteria. The data, altogether, indicated that the chitosan coating of IONP result in interface that enhances ROS production, hence the antimicrobial activity.

Effect of Surface Charge and Hydrophobicity Modulation on the Antibacterial and Antibiofilm Potential of Magnetic Iron Nanoparticles

“…The charge of the synthesized MNPs was −18 mV [8,31]. The XRD analysis (supplementary materials 2) showed typical pattern for maghemite ( -Fe 2 O 3 ).…”

“…Hydrophilic negatively charged particles showed insignificant antibacterial activity, while modulation of surface functional group to impart a strong positive charge (e.g., ATPMS-MNPs; 24.5 mV) enhanced the antibacterial activity [8,54,55]. This indicated that surface positivity imparts antibacterial potential on the particles.…”

“…Bacterial adhesion is mediated by electrostatic, dipole-dipole, H-bond, hydrophobic, and van der Waals interactions [8]. Biofilms promote antibiotic tolerance by reducing antibiotic entry into the bacterial cells.…”

“…MNPs showed insignificant antibacterial activity [8,37,39]. Two physicochemical attributes were compared, namely, the surface charge and the hydrophobicity of the MNPs.…”

The antimicrobial activity of nanoparticles: present situation and prospects for the future

“…However, at higher concentrations, negatively charged NPs have a certain level of antibacterial activity due to molecular crowding, which leads to interactions between the NPs and the bacterial surface. 162 …”