| Improved corneal epithelial cell growth over artificial cornea materials is required to improve device retention within the eye. In this work, varying concentrations of epidermal growth factor (BGF), a potent mitogen for epithelial cells, were immobilized to polydimethylsiloxane (PDMS) substrates, and the cellular response was analyzed.;Three methods were developed to bind EGF to PDMS via polyethylene glycol (pEG) tethers. (1) Plasma Modification: EGF was first reacted with homobifunctional NHS2PEG and then bound to allylamine plasma-modified PDMS. (2) Hydrosilylation: PDMS was modified with heterobifunctional allyl-PEG-NHS and then EGF was attached to the surface-bound PEG. (3) Thiol Modification: EGF was first reacted with heterobifunctional NHS-PEG-maleimide and then bound to thiol-modified PDMS.;Using Method 1 (Plasma Modification), 40 to 90 ng/cm2 of EGF was bound, however 70% of this was adsorbed even under optimized EGF-PEG reaction conditions. Cells rapidly grew to confluence on these surfaces, and cell counts increased significantly compared to control surfaces. Extracellular matrix protein production was also increased on the EGF-modified surfaces, corresponding to significantly higher levels of cell adhesion observed under a detachment force.;Modification by Method 2 (Hydrosilylation) resulted in 10 to 300 ng/cm 2 of bound EGF, of which 20% was adsorbed. However, despite increased EGF binding homogeneity, the cell growth was slower on these surfaces than on those prepared by Method 1, and coverage was non-uniform at all EGF concentrations. This is likely due to a higher underlying PEG density, and binding of the PEG and EGF in clusters on the surface. Simultaneous tethering of the cell adhesion peptide YIGSR had no further effect on cell coverage.;Using Method 3 (Thiol Modification), 24 to 65 ng/cm2 of EGF was bound, of which 22% was adsorbed. This method enables more homogeneous EGF surface binding than Method 1, with a lower PEG density than Method 2. However, free thiol groups were inhibitory to corneal epithelial cell growth, even in the presence of bound EGF. Defunctionalization of freethiols by reaction with 3-maleimidopropionic acid restored cell growth and morphology on the PDMS, and may hence allow for retention of the proliferative effect of the EGF.;These results indicate that while tethering of EGF to PDMS can improve the coverage by corneal epithelial cells, and presents a promising strategy for modification of polymeric artificial cornea materials, the effects are highly dependent on the underlying surface chemistry. |
