Aptamers are oligonucleotides (DNA or RNA) that bind to chemical and biological analyte targets via affinity interactions. Through an in vitro synthetic process, aptamers can be developed for an extremely broad spectrum of analytes, such as small molecules, proteins, cells, viruses, and bacteria. Target recognition by aptamers is highly selective, as affinity interactions result in secondary aptamer conformational structures that specifically fit the target. The aptamer-target binding is also reversible and depends strongly on external stimuli such as pH and temperature. The specificity and stimuli-responsiveness of aptamers are highly attractive to biological purification and sensing, which generally involve isolating minute quantities of targets from complex samples with non-specific molecules and impurities present at orders-of-magnitude higher concentrations. We present an aptamer-functionalized microfluidic platform that by design exploits the specificity and temperature-dependent reversibility of aptamers to enable biomolecular purification and sensing. Using the specificity of aptamers, we demonstrate highly selective capture and enrichment of biomolecules. Employing thermally induced, reversible disruption of aptamer-target binding, we accomplish isocratic elution of the captured analytes and regeneration of the aptamer surfaces, thereby eliminating the use of potentially harsh reagents. Using integrated microfluidic control, the eluted analytes are detected in a label-free fashion by mass spectrometric methods.

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