Mechanical Property Change Induced by Chemical Modification of PDMS Influences Stem Cell Behavior

Polydimethylsiloxane (PDMS) has been widely used in bio-micro-electro-mechanical systems (BioMEMS). In order to realize assembly of the devices or render a hydrophilic surface for cell adhesion, the PDMS surface has to be modified, usually using oxygen plasma. We revealed that oxygen plasma treatment not only changed the surface chemistry but topographical and mechanical properties. The mechanical property change has a predominant effect, overriding the chemical and topographical factors, on focal adhesions, proliferation, and differentiation of human mesenchymal stem cells (hMSCs). Immunostaining and western blot analysis showed that the increase in the substrate stiffness has no obvious influence on the early stage Arp2/3 complexes, but significantly promoted the formation of focal adhesions. The enhanced focal adhesions favored cell spreading, consequently proliferation and differentiation of hMSCs.