Nanotechnology Detects Antibodies in Blood

A rapid and easy-to-use diagnostic test consists of a nanometer-scale DNA "switch" that can quickly detect antibodies specific to a wide range of diseases.

The test may aid efforts to build point-of-care devices for quick medical diagnosis of sexually transmitted diseases (STDs), allergies, autoimmune diseases, and a number of other diseases.

Bioengineers at University of California (Santa Barbara, CA, USA) and the University of Rome Tor Vergata (Italy) developed a versatile electrochemical switch that supports the rapid, quantitative detection of antibodies directly in whole blood at clinically relevant low-nanomolar concentrations. The design of the switch takes advantage of the occurrence of two antigen-binding sites on each antibody, which are separated by about 12 nm. Specifically, they used DNA to engineer a switch that brings into the close proximity of less than 4 nm two copies of an antigen, epitope, or hapten via the formation of a stem-loop structure.

The team built synthetic molecular switches that signal their state via a change in electric current. This change in current can be measured using inexpensive electronics similar to those in the home glucose-test meter used by diabetics to check their blood sugar. The scientists used these nanoswitches to detect anti-HIV antibodies directly in whole blood in less than five minutes.

This new class of electrochemical switches is versatile, as they support the use of both small-molecule haptens and polypeptide epitopes for antibody detection. The investigators believe that they can likely be engineered to support the detection of even nonantibody targets as long as the targets present two or more recognition sites spaced far enough apart to induce the required stem opening.

Francesco Ricci, PhD, a professor at University of Rome Tor Vergata and cofirst author of the paper, said "A great advantage of these electrochemical nanoswitches is that their sensing principle can be generalized to many different targets, allowing us to build inexpensive devices that could detect dozens of disease markers in less than five minutes in the doctor's office or even at home." The study was published on August 22, 2012, in the Journal of the American Chemical Society.

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University of California
University of Rome