Responsive Polymer Brushes as Tools for Modulating Biointerfaces

Smart surfaces that can tune their properties in response to a trigger have aroused massive interest in science and technology. The surfaces are based on self-assembled monolayers or polymer brushes, macromolecular assemblies tethered to a surface by one end, that can reversibly alter their properties by applying stimuli- such as pH, light and electrical potential. These surfaces have been particularly instrumental in the in vitro studies of the dynamic properties of biological systems. Electrical potentials, in particular, has been used as an active stimulus that triggers specific conformational transitions in the surface-bound molecules to facilitate rapid and reversible switching. Electrically switchable surfaces based on SAM has been proved to switch the cell adhesion reversibly. Herein, a novel surface based on gold nanoparticles and polystyrene sulfonate (PSS) brush is designed to create a platform with more significant conformational changes enriching the application of the surface to other biological processes with larger proteins and biological entities involved. The surface can be further exploited to provide fundamental information about contributing processes and interactions in the understudying phenomenon. The thesis is presented in three parts encompassing the detailed study of the PSS brush, surface modification and cell adhesion on the surface at different potentials. PSS brushes at different grafting densities are prepared and the effect of grafting density and NaCl concentration, as the main constituent salt of the cell media, is studied on the polymer conformation. The surface changes are characterised with cyclic voltammetry (CV) as well as ellipsometry with the CV being introduced as a novel method to study the conformational changes of the polymer. The smart surface is developed by introducing gold nanoparticle and their modification with the RGD peptide and the response of the surface to cell adhesion at different potentials is studied. The result shows about 44% and 72% increase in the ...