Paper BI+NS-WeM1
Plasma-Enhanced Chemical Vapor Deposition of an Antibacterial Coating from an Essential Oil-Derived Precursor

Wednesday, November 1, 2017, 8:00 am, Room 12

Polymeric constructs, such as filtration membranes for water treatment and nanocomposite scaffolds for wound healing and drug release, are often chosen for their ideal bulk properties (e.g., porosity, mechanical strength, and chemical inertness). Challenges faced when using such materials in aqueous settings, however, include their hydrophobicity and propensity for bacterial attachment, leading to biofilm formation and degradation of material performance. Modifying the surface of the constructs while simultaneously maintaining the bulk properties offers both the possibility of addressing these limitations and the potential for creating new advanced materials. Plasma processing is a valuable tool often used to improve material wettability and deposit antifouling coatings. Here, plasma-enhanced chemical vapor deposition is used to deposit films from eucalyptol (1,8-cineole), an antibacterial precursor derived from tea tree oil. Although the antibacterial properties of eucalyptol are supported by numerous clinical trials, it is unknown to what extent the monomer structure and biocidal capabilities are maintained in plasma polymerized films. Thus, we have explored the properties of the eucalyptol-based films as a function of plasma parameters (e.g., power, pressure). Surface analyses (contact angle goniometry, X-ray photoelectron spectroscopy, scanning electron microscopy, and optical profilometry) reveal film wettability directly correlates to precursor pressure, with water contact angles ranging from ~50° to 85°. To further improve wettability of these materials, they were subjected to H₂O (v) plasma modification, an approach that has been successful in past studies to improve polymer biocompatibility. After plasma treatment, wettability increased, with water contact angles of ~20-35°, and the films exhibited a significant enhancement in oxygen content (40-150%), while remaining stable in aqueous solutions. Attachment and biofilm formation assays allowed for assessment of bacterial interactions at 1 and 5 days after exposure, respectively, with gram-negative E. coli and gram-positive S. aureus. Using microscopy techniques, we observed attachment and growth are substantially diminished for as-deposited and H₂O (v) plasma treated films. Moreover, performance data (i.e., flux of coated ultrafiltration membranes) are presented. Surface analysis and performance testing results, combined with information about gas phase excited state species observed using optical emission spectroscopy, guide our development of additional antibacterial essential oil-based films for 2D and 3D constructs used in environmental and biomedical applications.