Light-activated affinity micropatterning of proteins on self-assembled monolayers on gold

We describe a method to pattern proteins onto a photolabile "caged" biotin-derivatized self-assembled monolayer (SAM) on gold, which we term light-activated affinity micropatterning of proteins (LAMP). LAMP is a multistep patterning process with considerable flexibility in its implementation. First, a reactive SAM on gold is formed from a mixture of 11-mercaptolandecanol and 16-mercaptohexadecanoic acid. Next, the carboxylic acid end groups in the SAM are coupled to methyl alpha-nitropiperonyloxycarbonyl biotin succinimidyl ester (caged biotin ester) through a diamine linker. The caged biotin is then deprotected in regions irradiated by masked UV light, and subsequent incubation with streptavidin results in selective binding of streptavidin to the irradiated regions. Micropatterning of various proteins has been demonstrated with a spatial resolution of similar to 6 mu m by confocal microscopic imaging of fluorophore-labeled proteins, and a contrast ratio of similar to 4:1 was determined by direct ellipsometric imaging of streptavidin. Immobilization of biotinylated antibodies on the streptavidin pattern indicates that LAMP can enable spatially resolved micropatterning of different biomolecules by repeated cycles of spatially defined photodeprotection of biotin, streptavidin incubation, followed by immobilization of the biotinylated moiety of interest.