Surface Chemical Functionalization of Wrinkled Thiol-ene Elastomers for Promoting Cellular Alignment

Wrinkled polymer surfaces find broad applicability; however, the polymer substrates are often limited to poly(dimethylsiloxane) (PDMS), which limits spatial control over wrinkle features and surface chemistry. An approach to surface functionalization of wrinkled elastomer substrates is demonstrated through versatile, multistep thiol-ene click chemistry. The elastomer is formed using a thiol-Michael reaction of tetrathiol with excess diacrylates while wrinkle formation is induced through a second free radical UV polymerization of the acrylates on the surface of the elastomer. Due to oxygen inhibition of the free radical polymerization, pendant acrylates at the surface remain unreacted and are subsequently functionalized with a multi-functional thiol, which can be further reacted through a number of thiol-X 'click' reactions. As a demonstration, these thiol surfaces are further modified to either promote cell adhesion of human mesenchymal stem cells (hMSCs) through coupling with RGDS-containing peptides or surface passivation through reaction with hydrophilic hydroxyl ethyl acrylate moieties. Through engineering a combination of surface chemistry and surface topography, hMSCs exhibited increased spreading and cell density on RGDS-functionalized surfaces and a two-fold increase in cell alignment when cultured on wrinkled substrates. Gradient functionalized surfaces created by tuning the wrinkle wavelength with UV irradiation enabled rapid screening of the effect of topography on the hMSCs. Further, this novel application of click chemistry enables simultaneous tuning of wrinkle topology and surface chemistry towards targeted material applications.