Effect of surface modification on protein retention and cell proliferation under strain

When culturing cells on flexible surfaces, it is important to consider extracellular matrix treatments that will remain on the surface under mechanical strain. Here we investigate differences in laminin deposited on oxidized polydimethylsiloxane (PDMS) with plasma treatment (plasma-only) vs. plasma and aminopropyltrimethoxysilane treatment (silane-linked). We use specular X-ray reflectivity (SXR), transmission electron microscopy (TEM), and immunofluorescence to probe the quantity and uniformity of laminin. The surface coverage of laminin is approximately 45% for the plasma-only and 50% for the silane-linked treatment as determined by SXR. TEM and immunofluorescence reveal additional islands of laminin aggregates on the plasma-only PDMS compared with the relatively smooth and uniform silane-linked laminin surface. We also examine laminin retention under strain and vascular smooth muscle cell viability and proliferation under static and strain conditions. Equibiaxial stretching of the PDMS surfaces shows greatly improved retention of the silane-linked laminin over plasma-only. There are significantly more cells on the silane-linked surface after 4 days of equibiaxial strain.