Rhamnolipid-capped iron oxide nanozyme-substrate combination as promising antibacterials of the new generation

Abstract Iron oxide nanozymes (Fe 3 O 4 NZs) have been promising in targeted drug delivery due to their peroxidase mimicry, biocompatibility, ability to interact with cell surfaces and cross membranes. Iron, being a crucial co-factor in Fenton reactions and biological pathways, serves as a ‘Trojan Horse’ stealthily entering cells and triggering powerful therapeutic responses. The stability and application-based performances of Fe 3 O 4 NZs had been improved with surface modifiers viz. PEG, PVP, dextran, dopants, etc. However, biosurfactants have remained untapped as capping agents for nanozymes. The present study explores the peroxidase mimicking properties of rhamnolipid-capped iron oxide nanozymes (RLFe 3 O 4 NZs), wherein the inherent antimicrobial properties of rhamnolipid enhance their applications. Transmission electron microscopy micrographs of chemically synthesized RLFe 3 O 4 NZs exhibit cubic structure, with Fourier transform infrared confirming rhamnolipid-iron oxide interaction. RLFe 3 O 4 NZs exhibit remarkable stability across 4 °C–65 °C and pH 2–8. With Michaelis–Menten constant ( K m ) of 3.16 mM, RLFe 3 O 4 NZs surpass horse radish peroxidase (HRP) ( K m = 3.7 mM) with superior catalytic efficiency. Offering resilience against external factors, the former represents an economical alternative to HRP. A biocompatible system integrating RLFe 3 O 4 NZs with minuscule-concentration of H 2 O 2 and KI have been introduced herein as potent antibacterials. This substrate combination generates reactive oxygen species, iodine species, and hypoiodous acid, which collectively disrupt bacterial quorum sensing and enhance antibacterial efficacy. RLFe 3 O 4 NZs effectively target both Gram-positive and Gram-negative bacteria at concentrations 25-folds lower than Fe 3 O 4 NZs. In vitro studies indicate inhibition in quorum sensing within 6 h of treatment. The strong antibiofilm properties of RLFe 3 O 4 NZs substantially impede bacterial integrity, cell size and intercellular linkages within the biofilm environment.