RATIONAL PATTERN DESIGN FOR IN-VITRO CELLULAR NETWORKS USING SURFACE PHOTOCHEMISTRY

The ability to create patterns of specific silane monolayers by deep ultraviolet lithography has been previously demonstrated, and preliminary attempts have been made to use these patterns to control adhesion and outgrowth of neurons and other types of mammalian cells. Here we report characterization of the mechanisms involved in these photoinitiated processes and their utility in various strategies for creating patterns for biologically relevant systems. We have divided the mechanisms into three general classes. The first is surface photolysis of the silane monolayer, which appears to proceed by a purely photochemical mechanism. The second mechanism involves direct photochemical conversion of a terminal functional group on a silane monolayer into a species with altered properties, e.g., the conversion of a thiol to a more oxidized form that inhibits the subsequent adhesion of proteins. The third is a photolytic degradation of the monolayer. The mechanisms have been probed by x-ray photoelectron spectroscopy, ellipsometry, and wettability measurements. One result of these investigations has been the development of better strategies to create patterns. Controlled growth of hippocampal neurons on high resolution patterns is presented as demonstration of the efficacy of these strategies in spatially dictating cell adhesion. These results have important implications in designing in vitro culture systems to study well-oriented neuronal systems.