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Plasma-Based Surface Modification of Polystyrene for Serum-Free Cell Culture

Surface treatments of polystyrene (PS), which are required to increase cell adhesion reproducibly in serum-free conditions and to maintain cell functionality, were performed using an atmospheric pressure dielectric barrier discharge (DBD) in nitrogen-containing gas mixtures: He/N2 and He/N2/H2. The resulting modifications analyzed by contact angle goniometry (CA), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) showed that plasma produced only minimal increases in the surface roughness while introducing the expected oxygen- and nitrogencontaining groups. In particular, amino groups on plasma modified PS were identified and quantified using chemical derivatization with 4-trifluoromethylbenzaldehyde (TFBA) and subsequent characterization with XPS. The treated surfaces became very hydrophilic but underwent partially hydrophobic recovery after 30 days of aging. The degree of recovery depended on the storage conditions of the substrates, in water or air environment. The biological behavior of HaCaT keratinocyte and SaOS-2 osteoblastic osteosarcoma human cells on corresponding substrates was accomplished by optical microscopy (OM), scanning electron microscopy (SEM) and alamar blue (aB) assay. Significant differences were found in the cell density and morphology of surfaces containing amino groups when compared to native PS. These results applied in vitro to cells in the absence of serum.