Buried, Covalently Attached RGD Peptide Motifs in Poly(methacrylic acid) Brush Layers: The Effect of Brush Structure on Cell Adhesion

Abstract

Iniferter-mediated surface-initiated photopolymerization was used to graft poly(methacrylic acid) (PMAA) brush layers obtained from surface-attached iniferters in self-assembled monolayers to a gold surface. The tethered chains were subsequently functionalized with the cell-adhesive arginine-glycine-aspartic acid (RGD) motif. The modified brushes were extended by reinitiating the polymerization to obtain an additional layer of PMAA, thereby burying the peptide-functionalized segments inside the brush structure. Contact angle measurements and Fourier transform infrared (FTIR) spectroscopy were employed to characterize the wettability and the chemical properties of these platforms. Time of flight secondary ion mass spectroscopy (TOF-SIMS) measurements were performed to monitor the chemical composition of the polymer layer as a function of the distance to the gold surface and obtain information concerning the depth of the RGD motifs inside the brush structure. The brush thickness was evaluated as a function of the polymerization (i.e., UV-irradiation) time with atomic force microscopy (AFM) and ellipsometry. Cell adhesion tests employing human osteoblasts were performed on substrates with the RGD peptides exposed at the surface as well as covered by a PMAA top brush layer. Immunofluorescence studies demonstrated a variation of the cell morphology as a function of the position of the peptide units along the grafted chains.

Metabolically Stable Cellular Adhesion to Inert Surfaces

“…In addition to the low background, a further advantage of poly(ethylene glycol)-polydimethylacrylamide (PEGA 1900 ) resin beads was the presence of long PEG tentacles that extend from the surface for optimal cellular interaction with attached adhesion molecules. [32] An unbiased library of heptapeptides (~20 000 compounds) that contained all 20 d-amino acid analogues of the natural gene-encoded amino acids, randomly selected at six positions and with a terminal ala, was synthesized on a PEGA 1900 resin [33] by the split-and-mix protocol in a dedicated multicolumn synthesizer. [34] The library was manually screened and sorted for adhesive peptides under a bright field microscope.…”

Fibroblast adhesion on ECM-derived peptide modified poly(2-hydroxyethyl methacrylate) brushes: Ligand co-presentation and 3D-localization

“…Navarro et al prepared RGD-functionalized poly(-methacrylic acid) brushes that differed with respect to the distance the cell adhesion ligands were positioned ("buried") from the brusheair interface. As compared to PMAA brushes that presented the RGD ligand at the top surface and which very well supported cell adhesion and proliferation, cells were found to adopt a rounded morphology on brushes that presented the buried ligands, indicating the importance of 3D presentation of cell-adhesive cues [33]. All of these results are of great interest and may help to generate advanced 3D cell culture scaffolds and ultimately contribute to improved tissue regeneration strategies.…”

Swelling Behavior and Nanomechanical Properties of (Peptide-Modified) Poly(2-hydroxyethyl methacrylate) and Poly(poly(ethylene glycol) methacrylate) Brushes

“…The combination of these two elements -preserving mass balance between dry and solvated brushes, and using the amount (volume fraction) of water entering the brush to govern the total swelling of the brush -significantly constrain the 11 fitting by limiting the number of adjustable parameters. Perhaps more importantly, these constraints help to develop a credible physical representation of the solvated brush system.…”