A Highly Selective Electrochemical DNA-Based Sensor That Employs Steric Hindrance Effects to Detect Proteins Directly in Whole Blood

Sahar Sadat Mahshid, Sébastien Camiré, Francesco Ricci, Alexis Vallée-Bélisle

The development of rapid, low cost, easy-to-use approaches for the quantitative detection of multiple biomarkers would drastically impact global health by enabling medical diagnosis at the point-of-care. Unfortunately, current multiplexed methods for the quantitative detection of antibodies or other disease markers (e.g., enzyme-linked immunosorbent assays (ELISAs), Western blots, fluorescence polarization assays) remain complex multiple-step assays that rely on well-trained technicians and expensive instrumentations. As a promising alternative, we describe here a novel signal transduction mechanism for the one-step detection of any large macromolecules (e.g. antibodies) that utilizes steric hindrance effects at the nanoscale. More specifically, this homogenous assay takes advantage of the large dimension of macromolecules in comparison to the diameter of a double stranded DNA helix: upon binding to a signaling DNA strand that contain a small recognition element, the relatively large macromolecule will reduce the number of signaling strands that can hybridize on its complementary sequence immobilized on a surface. Here we demonstrate this steric hindrance hybridization assay using an electrochemical readout (eSHHA) and show that it enables the quantitative, one-step detection of four different macromolecules in the low nanomolar range in less than 10 minutes directly in whole blood. This inexpensive eSHHA sensor can be readily multiplexed and used for the point-of-care detection of any proteins for which we possess a small recognition element that we can attach to DNA.