Plasma lithography--thin-film patterning of polymers by RF plasma polymerization II: Study of differential binding using adsorption probes.

In this study we present methods to physico-chemically modify micropatterned cell culture substrates that were manufactured using plasma lithography to incorporate affinity structures for specific cell binding. The surfaces consist of a pattern of a fluorocarbon plasma polymer with feature sizes between 5 and 100 microm on a background of a non-fouling tetraglyme (tetraethylene glycol dimethyl ether) plasma polymer. The tetraglyme polymer blocks virtually all non-specific binding of proteins, and it is non-adhesive for a fluorocarbon-polyethylene glycol (FC-PEG) surfactant designed to act as a 'hydrophobic anchor' for peptides. The surfactant shows a strong affinity for the fluorocarbon polymer pattern, thus enabling us to form a pattern of the surfactant-conjugated peptide. To verify this, we have synthesized a conjugate between histamine (as a model for a more complex peptide) and a commercially available FC-PEG surfactant. Disuccinimidyl carbonate was used to activate the terminal -OH group of the polyethylene glycol headgroup for the reaction with the amine-containing molecule. Affinity pattern formation can easily be achieved by immersion of the patterned substrates in a solution of the peptide-surfactant conjugate. Time of flight secondary ion mass spectroscopy in the imaging mode was used to verify that the surfactant localizes on the pattern, while the background remains bare. A model protein, bovine serum albumin, showed the same behavior. This suggests that these surfaces can be used for the formation of patterns of cell-adhesive proteins. These substrates will be used to investigate the influence of the cell size and shape of vascular smooth muscle cells on their physiology.