Light-activated affinity micropatterning of proteins

Protein micropatterning has attracted considerable interest because of its prospective application in the fabrication of biosensors and tissue engineering substrates. Motivated by these potential applications, we have developed a method to micropattern proteins onto self-assembled monolayers (SAMs) on gold, which we term light-activated affinity micropatterning of proteins (LAMP). LAMP is a multi-step patterning process: first, a gold substrate is modified with a mixture of 11-mercaptoundecanol and 16-mercaptohexadecanoic acid to provide a non-fouling, reactive SAM template on gold. Next, the carboxylic acid terminal groups in the binary SAM are coupled to methylnitropiperonyloxy-carbonyl biotin, ("caged" biotin) through a diamine linker, resulting in a mixed MeNPOC-biotinyl/OH-terminated monolayer. Activation of the caged biotin by spatially-defined UV illumination at 350-360 nm reconstitutes biotin in the illuminated region, allowing streptavidin or anti-biotin antibody to be localized in the illuminated regions. We have investigated each fabrication step in LAMP by a variety of surface analytical techniques, including contact angle goniometry, ellipsometry, surface plasmon resonance, and X-ray photoelectron spectroscopy to optimize ligand density and pattern contrast. LAMP can be further extended to spatially-resolved micropatterning of multiple biomolecules by repeated cycles of spatially-defined activation, streptavidin incubation, followed by binding of the biotinylated moiety of interest.