Bioactivation of Plane and Patterned PDMS Thin Films by Wettability Engineering

Abstract

This study shows how surface properties of polydimethylsiloxane (PDMS) thin films, such as wettability and cellular adhesive behavior, can be influenced by surface modification and patterning, to improve the suitability of such modified PDMS for biomedical applications. For that purpose, different types of PDMS (i.e., soft (S-) and hard (H-) PDMS) and differently patterned surfaces were prepared by a commercially available tool which is originally used to produce patterned PDMS stamps for substrate conformal imprint lithography. To increase surface wettability and cellular adhesive behavior, PDMS surfaces were modified by O2, Ar/O2, Ar, and forming gas (N2/H2) plasma treatment. It is shown that, especially, plasma treatment using N2/H2 is a promising method to modify PDMS surfaces towards enhanced wettability. Such modified PDMS surfaces exhibit water contact angle values (WCA) of nearly 0° and demonstrate enhanced attachment of melanoma cells. Differences between as-prepared and plasma-treated S- and H-PDMS can be observed, where H-PDMS shows smaller WCA than S-PDMS. Even plasma-treated PDMS surfaces, however, exhibit only temporary hydrophilicity, due to hydrophobic recovery. To overcome this problem, plasma-treated PDMS films were stored in ethanol and water, where low and constant WCAs for several months could be achieved. Finally, the influence of surface topography of different patterned PDMS thin films on the adhesion behavior of melanoma cells was investigated. It can be concluded that chemical as well as structural modifications of PDMS enable to gradually control the adhesive properties of cells on their surfaces. This has a high technological impact since regulated and topologically stable adhesion and repulsion of cells by their scaffolds has high potency for in vitro as well as in vivo applications.