Toward Plasmonic Biosensors Functionalized by a Photoinduced Surface Reaction

We present a method for efficient coupling of amine nucleophilic molecules of choice to a nanostructured gold surface via photoinduced surface chemistry. The method is based on photoactive self-assembled monolayers and can be used to functionalize localized surface plasmon resonance (LSPR) based biosensors with biorecognition motifs while reducing nonspecific binding via introduction of hydrophilic units. The photoactive linker molecule, 5-bromo-7-nitroindoline, couples nucleophilic molecules such as biotin ethylenediamine to a surface when exposed to UV-light. The specific, noncovalent recognition between biotin and streptavidin is used for demonstration of a simple biorecognition assay based on the LSPR sensing principle. By doing so, one can envision that the binding of any streptavidin fusion protein, being attached to specific spots at the gold surface, is monitored by an LSPR peak shift. Since the surface functionalization is based on a photoinduced reaction, this method can be used to functionalize the surface in a local and site-specific way, and biomedical applications such as drug-screening platforms, microarrays, solid support protein synthesis, and even single molecule experiments can be envisioned