Atmospheric pressure deposition of micropatterned nitrogen-rich plasma-polymer films for tissue engineering

A novel atmospheric-pressure plasma-polymerised thin film material has been deposited on various substrates using a pilot scale dielectric barrier discharge (DBD) reactor. Deposition kinetics and physico-chemical 1 characterisation data of nitrogen-rich plasma-polymerised ethylene (PPE:N) films, obtained using feed gas mixtures of N-2 (ca. 10 slm) and C2H4 (ca. 10 seem) are described. Nitrogen concentrations, [N], in the PPE:N films up to ca. 40% were determined by XPS; the concentrations of N-functionality of greatest interest, primary amines, were determined by chemical derivatisation with 4-trifluoromethyl-benzaldehyde. The PPE:N films were further characterised by attenuated total reflectance infra-red spectroscopy (ATR-FTIR), contact angle goniometry, and atomic force microscopy (AFM). Square arrays of PPE:N "islands", for example 30 mu m in diameter repeated every 200 gm, were deposited on polymers, for example biaxially oriented poly(propylene) (BOPP), through specially-prepared Kapton (R) polyimide masks. Cell culture experiments were then conducted on these micro-patterned surfaces, using various cell types of interest in orthopaedics, for example growth plate and articular chondrocytes, or human U937 macrophages, the latter of which do not adhere to existing cell culture dishes. In all these cases the cells rapidly adhered and proliferated on the PPE:N islands, but not elsewhere on the polymer surfaces. In an effort to gain insight into cell adhesion mechanisms, adhesion of both macrophages and chondrocytes was tested against films with different [N] values. U-937 macrophages adhered to films containing 25% or more [N], but not at all to films with lower values of [N], suggesting the existence of a "critical" value, [N](crit), necessary to induce cell adhesion.