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

## TL;DR

This study shows that coating iron oxide nanoparticles with chitosan increases their ability to kill bacteria by boosting reactive oxygen species production.

## Contribution

The novel finding is that surface modification of iron oxide nanoparticles enhances their antimicrobial activity through increased ROS production.

## Key findings

- Negatively charged iron oxide nanoparticles showed insignificant antimicrobial activity against tested bacteria.
- Chitosan-coated nanoparticles significantly increased antimicrobial activity and reactive oxygen species production.
- Surface modification with chitosan alters the nanoparticle-bacteria interface to enhance bacterial killing.

## 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.