Summary: 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 characterisation data of nitrogen‐rich plasma‐polymerised ethylene (PPE:N) films, obtained using feed gas mixtures of N2 (ca. 10 slm) and C2H4 (ca. 10 sccm) 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‐trifluoromethylbenzaldehyde. 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 μm in diameter repeated every 200 μm, were deposited on polymers, for example biaxially oriented poly(propylene) (BOPP), through specially‐prepared Kapton® 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.

Degenerative disc disease has been implicated as a major component of spine pathology. However, although biological repair of the degenerate disk would be the ideal treatment, there is no universally accepted scaffold for tissue engineering of the intervertebral disk. To help remedy this, we investigated the gelation kinetics of various concentrations (2.5 to 10%) of two water-soluble chitosan chlorides (low molecular weight Protasan UP CL113 and high molecular weight Protasan UP CL213) and two chitosan glutamates (low molecular weight Protasan UP G113 and high molecular weight Protasan UP G213). Various concentrations (5 to 20%) of genipin, a naturally occurring cross-linking reagent used in herbal medicine and in the fabrication of food dyes, were used to prepare cross-linked chitosan hydrogels. The results show that 2.5% Protasan UP G213 cross-linked to 5% genipin was the best candidate. This formulation gelled fastest at 37 degrees C, and maintained 95% viability of encapsulated cultured disk cells. The gel did not produce an inflammatory reaction when injected subcutaneously into C57BL/6 mice and is therefore biocompatible. Most importantly, when injected into the degenerated nucleus pulposus of human cadaveric intervertebral disk, the gel flowed into the clefts without leakage. This study demonstrates that 2.5% Protasan UP G213 cross-linked to 5% genipin might be a promising scaffold for disk tissue engineering.