Materials Science and Technology of Polymers at the University of Twente

DESIGNER POLYMER BRUSH LAYERS AS PLATFORMS FOR BIOINTERFACES
 

Iniferter-mediated surface-initiated photopolymerization was used to graft poly(methacrylic acid) (PMMA) brushes from self-assembled monolayers on gold surfaces. The PMAA chains were subsequently functionalized with the RGD cell-adhesive peptide sequence. RGD units were covalently immobilized both at the top of the brushes and within the brush layers after extension of the polymer chains by a further polymerization step. The stepwise fabrication/chemical modification of the brushlike platforms allowed us to control the brush composition in depth, as well as the position of the cell adhesive units within the polymer layers (Figure 1).

 

 

Figure 1. Preparation of designer polymer grafts using controlled polymerizations.

MG63 osteoblastic cells were used to evaluate the effect of RGD positioning within the brush. No significant differences were observed with the LDH-based adhesion study. However, there were noteworthy differences with respect to the cells’ morphology. Cells spread well with marked focal adhesion points at the periphery of the cytoplasm on samples with RGD motifs coupled on the surface, whereas in the case of the samples where RGD was buried, cells were found to adopt a rounded morphology and focal adhesions concentrated toward the internal part of the cell (Figure 2).

 


Figure 2. Schematic of the morphological changes of cells on a PMMA brush without RGD (A) and with RGD at different depths in the brush layer (B,C,).

These findings indicate that there is a direct correlation between the vertical position of the RGD motif and cell morphology. The evidence reported suggests that surfaces modified with well-defined, nanostructured polymer brushes can represent model platforms for the study of changes in the cell adhesion and morphology.

Publication Navarro, M., Benetti, E.M., Zapotoczny, S., Planell, J.A., Vancso, G.J. Buried, Covalently Attached RGD Peptide Motifs in Poly(methacrylic) Brush Layers: The Effect of Brush Structure on Cell Adhesion, Langmuir, 24, 10996 – 11002 (2008)