Programmed Affinity Extraction of Molecules on a Microfluidic Platform

Here, we present a "smart" microfluidic system for highly selective extraction of trace amounts of analytes using ribonucleic acid (RNA) aptamers. A micro-chamber consisting of streptavidin coated polystyrene beads was fabricated on a glass substrate using standard MEMS fabrication techniques. The beads were mobilized into the reaction chamber by an auxiliary channel and trapped using two weirs each connecting a sample carrier channel. After a thorough rinsing of the beads and chamber with buffer solution, a 20 muM solution of biotin labeled adenosine triphosphate aptamer (ATP-aptamer) was loaded into the chamber and allowed to bind with the streptavidin modified beads. An affinity matrix was realized. The extraction of an affinity analyte, adenosine monophosphate coupled with thiazole orange (TO-AMP), with acute discrimination, was demonstrated. Detection of the analyte was performed directly on the microfluidic device using an inverted fluorescence microscope. Additionally, we demonstrated "programmed" release and regeneration of the device using both competitive displacement and thermal energy. The effectiveness of both mechanisms is presented.