Synthesis of Antimicrobial Nanocomplexes Using Argon Plasma Chemistry

Abstract

Plasma chemistry was employed as first the oxidizing and then the reducing agent in separate steps of a surface modification approach. More specifically, argon plasma chemistry coupled with the “grafting-from” approach was used to engineer an innovative and antibiotic-free nanocomplex. Through covalent binding of monomeric acrylic acid to a substrate in a “bottom-up” approach, a negatively charged nanocoating forms upon exposure to solutions of 2 mM silver nitrate. Through electrostatic interactions, the polymer brushes of the nanocoating can specifically bind to Ag⁺, which creates a platform for the in situ reduction of Ag⁺ to Ag⁰ using only argon plasma technology. By controlling grafting-, reduction-, and metal-binding conditions, we can generate antibiotic-free anti-infection nanocomplexes with controllable grafting density, polymer brush length, and silver nanoparticle (AgNP) concentration and size. We have used this technology to engineer nanocomplexes with polymer brush densities of 70 μg/cm² and dry brush polymer lengths of 144 nm. Under appropriate experimental conditions, AgNPs with typical sizes of 50–100 nm are synthesized and bound to polymer brushes in the nanocoating. Using these immobilization platforms, very low amounts of AgNPs (2.46 μg/cm²) can be bound to the nanocoating. The resulting nanocomplexes were found to be extremely effective at eradicating S. epidermidis, E. coli, and S. aureus biofilms in vitro. The anti-infection nanocomplexes combat infections by directly dealing with attached bacteria to eradicate biofilm-associated infections. Results indicate that these biocompatible nanocoatings kill bacteria by interacting with the cell membranes of bacteria to cause cell death through lysis. These stable, biocompatible nanocoatings present a promising antibiotic-free strategy for preventing device-associated infections.