Patterned and switchable surfaces for biomaterial applications

Andrew Hook – Patterned and switchable surfaces for biomaterial applicationshowever, demonstrated the ability of this cell type to grow over the ethylene glycolregions.Hyun et al., [86] attempted to broaden the scope of CP by developing surfacechemistries that covalently react with the printed molecules. This was achieved byinitially functionalising the surface of carboxylic acid functional polymers. Thecarboxylic acid groups were activated by reaction with pentafluorophenol to formpentafluorophenyl esters. Stamping of an amine functionaised molecule with biotinfunctionality resulted in its covalent attachment; thus, a patterned surface of biotingroups was produced. Subsequent addition of streptavidin modified moleculesenabled the patterning of these molecules at the surface with micron resolution [86].Tween 20 or BSA were adsorbed to the surface in order to saturate the surface withprotein thereby minimising non-specific binding in between the printed regions. Asimilar technique was also used to initiate free radical polymerisation of PS bymodifying a gold plated surface with thiols with terminal carboxylic acidfunctionality, subsequently converted to a pentafluorophenyl ester, and then printinga radical polymerisation initiator with a terminal amine. The initiator attachedcovalently to the SAM by formation of an amide bond. This enabled the spatiallyconfined free radical polymerisation of PS at the surface upon addition of thepolymerisation solution [87]. Here, cells preferentially attached to the SAM ratherthan the surface grafted PS layer.In order to pattern cells upon a biodegradable surface, Kumar et al., [88] patterneda biocompatible chitosan substrate by CP of random copolymers of methacrylicacid (MAA) and oligo(ethylene glycol) methacrylate (OEGMA). This polymer notonly shows low fouling characteristics but, being an anionic polyelectrolyte, alsobinds through multivalent electrostatic interactions to the positively charged chitosan1-23