(537d) Creating Multimodal Bio-Substrates Via Chemical Vapor Deposition

Eyster, T., University of Michigan
Deng, X., University of Michigan-Ann Arbor
Lahann, J., University of Michigan

We have created and characterized complex bioactive surfaces using chemical vapor deposition (CVD) polymerization. CVD has several advantages over traditional methods for creating thin film polymers, including deposition of compounds onto substrates at near-room temperature and good conformality. Moreover, the process does not require a solvent to dissolve the monomer, and does not require an initiator for polymerization. Thus, CVD could be an ideal technique for producing complex surfaces on medical devices with complicated geometries functionalized with biomolecules such as small adhesion peptides and growth factors. In this work, CVD was used to coat a variety of substrates with a copolymer thin film of poly-p-xylylene functionalized with alkyne and pentafluorophenyl ester groups. The tri-peptide cyclic-RGD was immobilized using Huisgen's [1,3] dipolar cycloaddition, and epidermal growth factor (EGF) was tethered covalently by reaction with the highly reactive pentafluorophenyl ester groups to form amide bonds with primary amines present in EGF. FTIR and XPS confirmed the presence of the expected polymer structures, and immunofluorescence was used to confirm the presence of tethered EGF. We further demonstrated enhanced cell spreading capabilities of the complex surfaces using a HUVEC (human umbilical vein endothelial cells) lines. Cells on surfaces containing RGD or RGD+EGF showed significant spreading over cells on surfaces lacking this peptide. However, the HUVECs showed negligible EGF signaling as measured by immunofluorescence for phosphorylated EGF receptor (pEGFR). On the other hand, A431 cells, which is an epithelial carcinoma line, demonstrated significant pEGFR levels when cultured on surfaces containing tethered EGF, though this was reduced by the presence of RGD. Furthermore, the level of pEGFR was similar to that shown by A431 cells exposed to 1000 ng/ml of soluble EGF (with a measured soluble EGF EC50 value of ~17 ng/ml). This indicated an enhanced potency of tethered EGF surfaces over soluble EGF. In conclusion, CVD-coated surfaces featuring tethered RGD and EGF both enhance cell spreading and cell EGFR signaling, showcasing the potential of the CVD approach for creating multipotent biofunctional surfaces.