Laser-modified nanostructures of PET films and cell behavior.

The surface of polyethylene terephthalate (PET) films was irradiated using KrF excimer laser (λ = 248 nm) with different number of pulses at constant repetition rate. The adhesion behavior of L-929 fibroblast cells on the irradiated surface was investigated. The changes in films' morphology were characterized by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The hydrophilicity and both polar and dispersion components of the surface tension of the treated films were evaluated by contact angle and surface tension measurement techniques. The films roughness was evaluated by atomic force microscopy. AFM and SEM observations showed that a specific nanostructure was created on the laser-treated polyethylene terephthalate surface. Contact angle and surface energy measurements have indicated an increase in wettability of the laser treated samples up to 5 pulses as optimum result; while, by increasing the laser pulses beyond 5 pulses the hydrophilicity of laser treated samples dropped and the surface energy of the treated films was leveled off. Data from in vitro assays showed significant cell attachment and cell growth onto laser treated samples in comparison with the untreated films. Moreover, a number of fibroblast cells attached and proliferated onto treated PET films were achieved under optimum condition of 5 pulses which was significantly higher than the other treated samples.