Magneto-Catalytic Janus Micromotors for Selective Inactivation of Bacteria Biofilms

Abstract

Janus micromotors are a unique class of materials whose surfaces have two or more distinct physical properties, allowing thus for two types of chemistry to occur simultaneously. Judicious design of the micromotor structure allows to incorporate different functionalities in a single unit to adapt the propulsion behaviour along with the incorporation of specific receptors for a myriad of applications. Herein we report the preparation of graphene oxide (GO)/PtNPs/Fe2O3 Janus micromotors for highly selective capture/inactivation of gram-positive bacteria units and biofilms. The strategy is based on the combination of a lanbiotic (Nisin) with Janus micromotors. Lanbiotics are peptides composed of methyllanthionine residues with a highly selective antimicrobial activity towards multidrug resistant bacteria. Nisin is a natural compound normally used for food preservation, which display specific antimicrobial activity towards gram-positive bacteria. Such peptide can bind to lipid II unit of the bacteria membranes, damaging its morphology and releasing its contents. The coating of micromotors with GO impart them with a Janus structure for the subsequent asymmetric assembly of catalytic (PtNPs) and magnetic (Fe2O3) engines and results in an active rough layer for a higher loading of Nisin via covalent interactions. The micromotors possess adaptative propulsion mechanisms, including catalytic mode (PtNPs) in peroxide solutions or magnetic actuation (fuel free) by the action of an external magnetic field. The enhanced movement and localized delivery of the micromotors (both in catalytic and magnetic actuated mode) results in a 2-fold increase of the capture/killing ability towards Staphylococcus Aureus bacteria in raw media (juice, serum and tap water samples), as compared with free Nisin and static counterparts. The micromotor strategy display also high selectivity towards such bacteria, as illustrated by the dramatically lower capture/killing ability towards gram-negative Escherichia Coli. Unlike previous micromotors based strategies, this approach displays higher selectivity towards a type of bacteria along with enhanced stability, prolonged use and adaptative propulsion modes, holding considerable promise to treat methicillin resistant antibiotic infections, for environmental remediation or food safety, among others applications.