Abstract

A Paradigm Shift in Biosensing: Label-Free Measurements in Free-solution

Darryl Bornhop, Professor, Vanderbilt University

Paradigm shifts in chemical or biochemical science often result from an enabling breakthrough coming onto the scene. Yet, as the German philosopher Arthur Schopenhauer and others have noted; all new ideas or scientific theories pass through three stages. First, is ridicule; second, is violent opposition; and third, is acceptance being viewed as self-evident. Typically, acceptance of new methods (MS, NMR, etc.) has come with accumulating supportive evidence and only then the stated idea may be true. Scientists, being human, resist change and tend to view new with skepticism. This presentation will be aimed at demonstrating that label-free measurements in free-solution, by Back-scattering interferometry (BSI), can enable a paradigm shift in biosensing. BSI is a simple optical device consisting of a coherent source, microfluidic chip and detector. A unique multi-pass configuration allows BSI to transduce minute changes in the refractive index of a solution into equilibrium binding constants over six decades and universal, quantitative sensing at the zeptomole level. Examples will illustrate that BSI can be used to detect and quantify a wide array of biological analytes (antibody-antigen, protein-ion, protein-protein, aptamer-protein-aptamer interactions, DNA hybridization and membrane-associated protein drug targets within the native bilayer environment), at pM-fM levels, without labels or immobilization. It will be shown that free-solution operation of BSI comparable to fluorescent assay sensitivity in complex matrices, without analyte mass dependency, enables rapid assay development, low sample consumption, and the potential to expedite biomarker validation.