Local plasma activation of PS films with a defined design for biomedical use

In this work, air plasma treatment of polystyrene (PS) films was selectively carried out on a pre-defined pattern by using a micro-plasma needle set-up in an efficient one-step process. Patterns consisting of three vertical lines were selected during the plasma modification process. The space between the lines and the number of treatment repeats were modified and their influence on PS surface characteristics was investigated. The distribution of oxygen functional groups across horizontal sections was shown by performing X-ray photoelectron spectroscopy mapping measurements. These results were compared with water contact angle measurements and showed that increasing the number of treatment repeats leads to an improvement of the wettability and an increase of the percentage of oxygen incorporated in the center of the modified line regions. In addition, the width of the plasma treated lines was found to increase with increasing number of treatment repeats. Physical surface properties were also analyzed on pre-selected locations of the PS surface using atomic force microscopy. Finally, cell tests using human foreskin fibroblasts were carried out to investigate the effect of the plasma activated lines on cell attachment and proliferation. The number of treatment repeats and distance between the lines were found to strongly affect cell adhesion and proliferation. As such, the plasma needle set-up used in this work is able to noticeably improve PS biocompatibility on a pre-determined area by selecting the appropriate plasma operational parameters.