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.
Highlights
We found that p-IONP has higher antimicrobial activity than n-IONP
The findings conclude that n-IONP has antimicrobial activity at relatively very high concentrations
The activity can be further moderated by changing the surface potential and accessible surface functional groups
Summary
Intact IONPs upon contact with air loses its magnetism and monodispersibility[9] To avoid such problems, various research groups have taken the help of different chemical and biological agents to modify the surfaces, and stop the lose. Chitosan was chosen to coat IONP surface, since cationic hydrophilic chitosan polymer is well studied biocompatible molecule with inert chemical nature against air, and possesses amino group which interacts with hydroxide functional group present at the IONP surface[18]. The study aims to evaluate the antimicrobial propensity of chitosan coated IONP, which show insignificant anti-microbial activity when not coated with chitosan To this end, n-IONP was synthesised and coated with positively charged chitosan biomolecules, and their antimicrobial activity against a Gram positive (Bacillus subtilis) and a Gram negative (Escherichia coli) bacteria were studied using different techniques like bacterial growth kinetics, colony forming unit measurement, ROS, and BacLight fluorescence assay. IONP antimicrobial activity upon coating with biocompatible chitosan molecule and the underlying mechanism of antimicrobial activity have not been explored in detail
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