Environmentally Friendly Sterilization and Enhancement of Cellulose Using RF Plasma Process

Abstract

Cellulose-based materials are widely used in wound care due to their biocompatibility, biodegradability, and fluid-handling capacity. While chemical functionalisation is commonly employed to impart antimicrobial activity, the role of physical surface modification in regulating bacterial adhesion remains less explored. In this study, low-pressure radiofrequency (RF) oxygen plasma was used as a dry and environmentally friendly approach to modify the surface of medical-grade cellulose without altering its bulk properties. Plasma treatment was performed in both glow and afterglow regions, enabling controlled exposure to reactive oxygen species. Surface modification resulted in pronounced nanoscale roughening and fissured topography of cellulose microfibers, as observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Plasma-induced oxidation of the cellulose surface, characterised previously by X-ray photoelectron spectroscopy (XPS), accompanied the morphological changes. Bacterial adhesion experiments using a non-pathogenic Escherichia coli model strain revealed significantly enhanced bacterial attachment on plasma-treated cellulose compared to untreated controls, with the strongest effect observed for glow-region treatments. The increased adhesion is attributed to the combined effects of surface roughness amplification and plasma-induced chemical functionalisation, which together increase the effective contact area between bacteria and the substrate. Rather than aiming to inhibit bacterial attachment, this work explores a physico-mechanical design concept in which surface topography is intentionally modified to favour bacterial binding to the dressing material itself. The observed behaviour is interpreted qualitatively using concepts from membrane mechanics as a phenomenological framework, without invoking a quantitative predictive model. While the present study does not assess net bacterial load reduction in wound environments, it establishes a materials-level basis for a “capture-and-remove” hypothesis, whereby preferential bacterial adhesion to a removable dressing could contribute to microbial load management during dressing changes. These findings highlight the potential of plasma surface engineering as a versatile tool for tailoring the biointerface of cellulose-based biomedical materials.