Bifunctional SAMs as Templates for Microfluidic Screening Arrays

This research investigated the patterning of a bifunctional self-assembled monolayer (SAM) as a template for a microfluidics-based multiplexed screening array using microbeads spectrally encoded with quantum dots (QDs). Microcontact printing and direct UV exposure techniques were used to pattern islands of amine-terminated aminopropyltrimethoxysilane (APS) surrounded by a passivated region of methyl-terminated PEG-Silane on a silicon substrate. The amine groups were reacted with one end of the bifunctional linker NHS-PEG-NHS, and the other end was then reacted with amine-functionalized styrene microbeads to tether them to the substrate. Each microbead contains a ratiometric combination of QDs with different emission wavelengths that produces a spectral ‘barcode' identifying the receptor molecule attached to the bead surface. Fluorescently tagged target ligands passing over the microarray on the substrate selectively bind to specific receptors, and the spatially overlapping emissions of the QDs and the fluorophore can then be deconvoluted using a confocal microscope to identify the receptor-ligand complex.