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

Unmodified magnetic nanoparticles (MNPs) lack antibacterial potential. We investigated MNPs surface modifications that can impart antibacterial activity. Six MNPs species were prepared and characterized. Their antibacterial and antibiofilm potentials, surface affinity, and cytotoxicity were evaluated. Prepared MNPs were functionalized with citric acid, amine group, amino-propyl trimethoxy silane (APTMS), arginine, or oleic acid (OA) to give hydrophilic and hydrophobic MNPs with surface charge ranging from -30 to +30mV. Prepared MNPs were spherical in shape with an average size of 6-15 nm. Hydrophobic (OA-MNPs) and positively charged MNPs (APTMS-MNPs) had significant concentration dependent antibacterial effect. OA-MNPs showed higher inhibitory potential against S. aureus and E. coli (80%) than APTMS-MNPs (70%). Both particles exhibited surface affinity to S. aureus and E. coli. Different concentrations of OA-MNPs decreased S. aureus and E. coli biofilm formation by 50-90%, while APTMS-MNPs reduced it by 30-90%, respectively. Up to 90% of preformed biofilms of S. aureus and E. coli were destroyed by OAMNPs and APTMS-MNPs. In conclusion, surface positivity and hydrophobicity enhance antibacterial and antibiofilm properties of MNPs.