Atmospheric pressure plasma modified surfaces for immobilization of antimicrobial nisin peptides

In the field of antimicrobial surfaces, the development of environmentally-friendly surface treatments and industrially viable processes remains a challenging research objective. The use of atmospheric plasma treatments, especially dielectric barrier discharge (DBD) plasma deposition, is a promising technological approach to confer a thin antibacterial coating to a surface. The aim of this work is to investigate the potentiality of atmospheric plasma polymer organosilicon-based coatings as a reactive layer for the immobilization of biologically active molecules on stainless steel surfaces. In this context, an atmospheric-pressure DBD afterglow is used for the first time to functionalize a steel surface with chemical groups in order to attach biomolecules and this process is compared with a direct DBD discharge. The organosilicon-containing plasma interlayer confers a silica-like skeleton to the coatings for adhesion and stability. Composition of the plasma films before and after peptide immobilization has been characterized by Fourier transform infrared spectroscopy (FTIR), static secondary ion mass spectrometry (TOF-SIMS) and X-ray photoelectron spectroscopy (XPS).It is shown that the covalent immobilization of the antibacterial nisin peptides onto the organosilicon interlayer leads to adherent and protective antibacterial coatings on stainless steel as demonstrated against Gram + bacteria using ISO 12296 antibacterial test. Nearly 4 log10 reduction of Gram + strain was obtained compared to uncoated stainless steel. Importantly the antibacterial surfaces were resistant to several cleaning conditions. The later is significant as the stability of such antibacterial surfaces in close to real life conditions is a major concern.

► Amine- and amide-functionalized organosilica coatings were deposited by DBD afterglow and direct DBD.
► Nisin peptides were immobilized on these coatings by immersion in nisin solution.
► The antibacterial properties of these nisin-silica coatings were studied.
► DBD afterglow coatings show superior antimicrobial activity.
► Antimicrobial activity was retained after aging testing.