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‡, and Alexis Vallée-Bélisle*†
† Laboratory of Biosensors & Nanomachines, Département de Chimie, Université de Montréal, Montréal, Québec H3T 1J4, Canada
‡ Dipartimento di Scienze e Tecnologie Chimiche, University of Rome Tor Vergata, Rome 00133, Italy
J. Am. Chem. Soc., Article ASAP
Publication Date (Web): September 4, 2015
Copyright © 2015 American Chemical Society
Here we describe a highly selective DNA-based electrochemical sensor that utilizes steric hindrance effects to signal the presence of large macromolecules in a single-step procedure. We first show that a large macromolecule, such as a protein, when bound to a signaling DNA strand generates steric hindrance effects, which limits the ability of this DNA to hybridize to a surface-attached complementary strand. We demonstrate that the efficiency of hybridization of this signaling DNA is inversely correlated with the size of the molecule attached to it, following a semilogarithmic relationship. Using this steric hindrance hybridization assay in an electrochemical format (eSHHA), we demonstrate the multiplexed, quantitative, one-step detection of various macromolecules in the low nanomolar range, in <10 min directly in whole blood. We discuss the potential applications of this novel signaling mechanism in the field of point-of-care diagnostic sensors.
http://www.nouvelles.umontreal.ca/udem- ... g-dna.html
http://www.cbc.ca/news/technology/montr ... -1.3243022
Montreal scientists score possible breakthrough for rapid diagnostic medical tests
Technique using DNA and electricity can detect a dozen antibodies at once – all in minutes
CBC News Posted: Sep 25, 2015 5:00 AM ET Last Updated: Sep 25, 2015 8:48 AM ET
A simple and fast chemical process developed by scientists in Montreal could allow family doctors to one day use equipment as straightforward and cheap as a diabetic's blood sugar tests to diagnose a range of diseases in minutes from their offices, instead of waiting days for results to come back from a lab.
"What these tests are looking for is antibodies — proteins that are generated by the body in response to viruses or bacteria. The highlight of the technique we developed is you put a drop of blood on our electrodes, and in five or 10 minutes you can know if you have the antibody. And in principle, you can detect any antibody you want."
Vallée-Belisle and his team, working with a chemist from the University of Rome, came up with a way to detect antibodies by having them bind to loose, single strands of DNA. Those single strands then attempt to pair up with nearby complementary strands to form the characteristic DNA double helix.
The researchers designed the single DNA strands so that if no antibodies are present when they bind with their complementary pairs, a detectable electrical current flows. But if antibodies are present and attached to the loose strands, the current drops. The drop is so precisely measurable that the test can even be used to determine how much antibody is in a sample, instead of simply indicating its presence or absence.
They call the process "electrochemical steric-hindrance hybridization assay," or eSHHA, because it takes advantage of how the DNA molecules react in the presence of other larger particles, an effect known as "steric hindrance."
Biochemistry professor Kevin Plaxco of the University of California at Santa Barbara, who supervised Vallée-Belisle's previous postdoctoral work and who is himself an expert in electrochemical methods to detect antibodies, called the results "clever" and "very simple and elegant."
"They're detecting the molecules in a way that has some rather interesting advantages," he said Thursday.