Label-free microfluidic characterization of temperature-dependent biomolecular binding

We present a microfluidic approach to characterizing temperature dependent biomolecular binding. A ligand and its affinity receptor, one of which is surface-immobilized and the other remaining in solution, are allowed to achieve equilibrium binding in a microchip at a series of selected temperatures. The unbound molecules in solution are subsequently collected and analyzed with matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), yielding temperature dependent equilibrium binding profiles of the ligand-receptor system. As examples, the thermally dependent properties of equilibrium binding of adenosine monophosphate, platelet-derived growth factor and arginine vasopressin with their affinity nucleic acid aptamers were investigated. The binding profile obtained for each biomolecular system revealed highly temperature dependent zones in which affinity binding or dissociation occurs. These results demonstrate that our microfluidic approach, which does not use any molecular labeling groups, can potentially be used to characterize receptor-ligand binding for applications in biosensing, biomolecular purification, and drug development.