The human immune system recognizes pathogens by specific proteins on their surfaces. This detection principle is already used in medical tests. Such tests typically require relatively large amounts of sample material. For some tests, the target protein must be chemically modified by reagents. That requires time and well trained lab technicians. Now scientists have developed a biosensor one hundred times more sensitive than currently available tests in recognizing proteins that are characteristic for the clinical picture of specific diseases, according to the researchers.
The biosensor chip holds synthetic DNA molecules, which are negatively charged, in an aqueous salt solution. These long molecules are tethered at one end to a gold surface. The free end is labeled with a fluorescent marker, so it can be optically observed; and at the very tip the scientists can place a "capture probe," a molecule that fits together with the target protein like the key to a lock. Alternating electric potentials set the DNA molecules in motion, swinging back and forth between "standing" and "lying" states with regular changes in a tightly confined but intense field.
If the protein of interest is present in sample material placed on the biosensor chip, it will bind to the "key" molecule. And because this makes the DNA strands considerably heavier, their swinging motion will be noticeably slower. Precise confirmation of the identity of the captured protein can be deduced from measurements of this motion, since both the size and shape of the protein will affect the way the DNA molecules swing.
The scientists are currently working with a chip that can analyze 24 different proteins in parallel. "The potential to analyze, on a single chip, many proteins at once in terms of multiple parameters represents a significant advance," says Dr. Ulrich Rant, head of the project.
Possible application areas for this chip technology include medical diagnostics, drug development, and proteomics research. Further development is targeted toward completion of a pre-production prototype by the end of 2010.
COMPAMED.de; Source: Technische Universitaet Muenchen