Combinatorial screen of the effect of surface energy on fibronectin-mediated osteoblast adhesion, spreading and proliferation

In order to accelerate tissue-engineering research, a combinatorial approach for investigating the effect of surface energy on cell response has been developed. Surface energy is a fundamental material property that can influence cell behavior. Gradients in surface energy were created by using an automated stage to decelerate a glass slide coated with a self-assembled monolayer (SAM, n-octyldimethylchlorosilane) beneath a UV lamp such that the SAM is exposed to the UV-light in a graded fashion. UV exposure causes oxidation of the SAM such that a longer exposure correlates with increased hydrophilicity. This approach yielded substrates having a linear gradient in surface energy ranging from 23 to 62 mN/m (water contact angles ranging from 25° to 95°). Using the gradient specimen approach enables all surface energies from 23 to 60 mN/m to be screened on each slide. Before cell culture, surface energy gradients were coated with fibronectin to allow a study of the effect of surface energy on fibronectin-mediated cell response. Cells were seeded on the fibronectin-coated gradients and adhesion, spreading and proliferation were assessed with automated fluorescence microscopy. Surface energy did not affect initial cell adhesion at 8 h. However, the rate of proliferation was linearly dependent on surface energy and increased with increasing hydrophobicity. Cell spread area was unaffected by changes in surface energy over the majority of the gradient although cells were significantly smaller on the most hydrophilic region. These results show that fibronectin-mediated cell spreading and proliferation are dependent on surface energy and establish a new combinatorial approach for screening cell response to changes in surface energy.