Tuesday, September 29, 2009

Graphene May Serve as Building Block for Microscopic Biosensors

Filed under: Nanomedicine

Sheets of carbon latice one atom thick, known as graphene, are likely to become useful tools in a variety of biomedical applications. Researchers at Pacific Northwest National Laboratory and Yale University have developed a method to mesh DNA and graphene into nanoscale structures coupled with accompanying fluorescent molecules that help visualize the interaction.

Tests showed that the fluorescence dimmed significantly when single-stranded DNA rested on graphene, but that double-stranded DNA only darkened slightly - an indication that single-stranded DNA had a stronger interaction with graphene than its double-stranded cousin. The researchers then examined whether they could take advantage of the difference in fluorescence and binding. When they added complementary DNA to single-stranded DNA-graphene structures, they found the fluorescence glowed anew. This suggested the two DNAs intertwined and left the graphene surface as a new molecule.

DNA's ability to turns its fluorescent light switch on and off when near graphene could be used to create a biosensor, the researchers propose. Possible applications for a DNA-graphene biosensor include diagnosing diseases like cancer, detecting toxins in tainted food and detecting pathogens from biological weapons. Other tests also revealed that single-stranded DNA attached to graphene was less prone to being broken down by enzymes, which makes graphene-DNA structures especially stable.

Image: An illustration of how fluorescent-tagged DNA interacts with functionalized graphene. Both single-stranded DNA (A) and double-stranded DNA (B) are adsorbed onto a graphene surface, but the interaction is stronger with ssDNA, causing the fluorescence on the ssDNA to darken more. C) A complimentary DNA nears the ssDNA and causes the adsorbed ssDNA to detach from the graphene surface. D) DNA adsorbed onto graphene is protected from being broken down

Press release: Graphene bolsters battery work, biosensors...

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