Wettability Modification of Electrospun Poly(epsilon-caprolactone) Fiber Surfaces by Femtosecond Laser Irradiation.

摘要

Surface wettability of polymeric scaffolds has been shown to have strong influence on biological interactions such as cell attachment, proliferation and differentiation. Thus, processes with the capability to flexibly control and pattern surface wettability of polymeric scaffolds are of great interest. Since femtosecond (FS) laser ablation is advantageous for fabrication of a variety of polymeric biomedical devices, an added ability to tailor polymer scaffold surface wettability properties concurrently with device fabrication would significantly improve flexibility for design and fabrication of improved polymeric scaffolds.;Electrospun (ES) PCL fibrous scaffolds have received considerable attention for tissue engineering applications because their surface and mechanical properties can resemble those of extracellular matrix. In the research presented in this dissertation, FS laser irradiation is being thoroughly investigated as a flexible and convenient method for patterned modification of the wettability of ES PCL fiber surfaces. Such a process for controlling the wettability on ES PCL fibers has not been reported previously.;Modification of the wettability of ES PCL fiber scaffolds surfaces over a wide range of water contact angles was produced by scanned FS laser irradiation under different conditions. The effects of various laser ablation process parameters and different gas atmospheres were investigated. Fiber surface chemistry and surface morphology were found to be altered simultaneously when scaffold surfaces were ablated by a scanned FS laser beam. Surface roughness and surface chemical state were characterized, since the wetting of a liquid drop on a solid surface depends mainly on two properties: the surface energy, determined by the chemical composition of the topmost molecular layer of the solid, and the surface morphology. Surface oxidization was shown to contribute to increased hydrophilicity of FS laser-structured ES PCL fiber substrates. The independent effects of surface morphology change and chemistry change on the wettability of ES PCL fiber substrates were investigated by nanometer-scale gold-coating the tested surfaces to exclude the effect of surface chemistry variation. Surface morphology change and surface chemistry change were found to have independent hydrophilic effects that increased with laser power. The Cassie-Baxter model was found to accurately predict the contact angles of gold-coated surfaces from morphology measurements.;The wettability modification of the ES PCL fiber surfaces treated by FS laser irradiation was found to undergo an ageing process. The contact angles of water droplets on the FS laser-treated fiber surfaces increased gradually over time and became stable towards some limiting value after ∼10 days. The limiting values were found to be close to those obtained on the gold-coated untreated and treated surfaces with different laser powers. Surface chemical states were found to undergo ageing and the chemistry modification effects on the un-coated fiber surfaces were all gone after the ageing process ceased, when the contact angles became stable and equal to the values of the gold-coated fiber surfaces treated for each treatment laser power level.