Washington [US], April 19 : An electronic biosensor based on DNA aptamers developed by a team of researchers can detect biomarkers in whole blood samples without the use of reagents. DNA aptamers recognise marker proteins as well as antibodies, but they are simpler to prepare and more adaptable. Without any additional sample preparation, the biosensor detected clinically relevant levels of a marker protein for cardiovascular disease.
The findings of the study were published in the journal Angewandte Chemie.
Researchers are interested in developing diagnostic tools that can detect disease biomarkers directly, reliably, and in the field, without requiring samples to be sent to specialised laboratories for analysis. Shana O. Kelley of the University of Toronto in Canada and Northwestern University in Evanston, IL, USA, and her colleagues created a simple chip-based device that uses chronoamperometric measurements to detect marker proteins in complex samples. Their nanoscale sensor system functions as a molecular "pendulum," measuring the extra load placed on the pendulum, which is made up of a strand of DNA tethered to an electrode. There are no external reagents required for this method.
Typically, antibodies are used to seek out and bind marker proteins in complex mixtures. However, antibodies are themselves proteins, and as such are quite complex to design and produce. Kelley and colleagues have now found that the smaller and simpler DNA aptamers can be used instead of antibodies. DNA aptamers are short synthetic fragments of with specific shapes and structures. They are relatively easy to make and, with customizable structures, cheaper to produce than antibodies.
Like antibodies, DNA aptamers can bind marker proteins through molecular and structural interactions, but they are easier to design. "DNA has the most predictable and programmable interactions of any natural or synthetic molecule," explain Kelley and her team. To develop an aptamer-based sensor, they created a DNA aptamer that specifically detects B-type natriuretic peptide (BNP), a biomarker for cardiovascular disease, and linked this aptamer with the DNA pendulum strand tethered to the gold electrode to create the molecular pendulum sensor.
The completed biosensor successfully detected BNP, even in complex mixtures such as unprocessed whole blood from cardiac patients. Because Kelley and colleagues found that the sensitivity of the aptamer-based system was as high as that of antibody-based detection, they suggest further research and use of DNA aptamers for laboratory-independent diagnostics.
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