Abstract

Aptamer-Based Assays Combined with Backscattering Interferometry Enables Field-Setting Quantification of Nerve Agent Metabolites and Human Cytomegalovirus in Urine

Darryl Bornhop, Professor, Vanderbilt University

Backscattering interferometry (BSI) is a method for detection of molecular interactions that holds promise for translation to the near-patient setting. BSI is quantitative at femtomolar (fM) sensitivity, requires nanoliter sample volumes and is “label free” using either the free-solution or tethered-probe mode. We have demonstrated < 15% coefficient of variation on a range of clinical sample matrices, including serum, saliva, and urine. BSI transduces changes in structure upon target binding, thus it is well-suited for use with aptamers, DNA or RNA probes that undergo significant structural changes upon binding. We will describe the principles of operation for BSI and show two examples of aptamer-enabled BSI detection relevant to near-patient diagnosis. The first example is the quantification of methylphoshonate metabolites of two nerve agents, where the aptamer-BSI assay for “VX-acid” and “GB-acid” yielded low nanomolar LOQ values with high selectivity and minimal cross-reactivity. Second, we demonstrate a picomolar LOQ in urine for aptamers binding to two major structural proteins of human cytomegalovirus: glycoprotein B, “gB” or the viral protein “pp65”. The probe volume detection limit for this determination is several thousand target-aptamer species, opening the avenue to early detection of CMV. These assays illustrate the potential for using these proteins as biomarkers of disease. An approach to constrain environmental noise in interferometry will also be presented, which is anticipated to lead to a bench-top, ruggedized, miniaturized molecular interaction photometer enabling use by the unskilled operator.