A physicochemical approach to render antibacterial surfaces on plasma-treated medical-grade PVC: Irgasan coating

Abstract

A multistep physicochemical approach was adopted to develop a novel surface active antibacterial medical-grade polyvinyl chloride (PVC). This was accomplished through surface activation via diffuse coplanar surface barrier discharge plasma in air at ambient temperature and pressure, followed by radical graft copolymerization of acrylic acid onto the surface via grafting-from pathway to yield a well-defined high density brush. Irgasan as a potent biocide was then coated onto the functionalized surface to impart antimicrobial properties. Contact angle measurements showed an improved hydrophilicity upon multistep modifications. Alterations in surface free energy values were tracked through various known models. The equilibrium water absorption test corroborated the contact angle analysis. Scanning electron microscopy revealed etched features on the plasma treated sample as well as a brush-like pattern on the graft copolymerized surface. Surface chemistry was explored by Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) and X-ray Photoelectron Spectroscopy (XPS), which confirmed the presence of irgasan non-covalently anchored onto the surface. An excellent bacteriostatic performance was exhibited by the irgasan coated sample using the agar diffusion test method against two potentially pathogenic gram-negative and particularly gram-positive bacterial strains implying a facile release of the antibacterial agent. However, in vitro bacterial adhesion and biofilm formation assays indicated incapability of irgasan in hindering the adherence after 24 h incubation. Nevertheless, the plasma treated and graft copolymerized samples were appreciably effective to diminish the adherence of gram-negative strain. Wettability and surface configuration of the substrate, besides bacteria structural characteristics, were established to be crucial factors in the adhesion phenomenon. The irgasan coated medical-grade PVC was suggested to be suited for use in disposable medical catheters of dependable antimicrobial performance.