As reported in the Science article, the new biosensor is able to detect many of the classic biological reactions that involve the recognition and binding of one molecule to another partner molecule.

In their tests, for example, the biosensor was able to match tiny concentrations of specific DNA sequences to its complementary strand, suggesting a potential role for a variety of genetic studies and tests, including DNA fingerprinting for clinical and forensic applications. Another biosensor proved sensitive to the binding of certain antibodies, manufactured by the body's immune system, to small amounts of their specific antigens--a class of molecules produced by invading organisms that include viruses, bacteria, in addition to toxins and allergens.

The biosensor was able to detect DNA concentrations at levels of down to 9 femtograms per square millimeter. (A femtogram is a millionth of a billionth of a gram.) By comparison, current technologies are only capable of detecting amounts about 100 to 1,000 times greater than the new biosensor.

"We have found nothing as simple or practical as this device with as much sensitivity," said Ghadiri. "The results show that we can sense very small molecules that in other systems do not produce a very big change. In our system, we see a huge change."

The new biosensor is based on work conducted during the past few years in Sailor's laboratory with porous silicon, small chips of silicon sculpted through a chemical etching process into a forest of tiny trees. When a one centimeter-square of this silicon forest is stretched out, its surface area would be about as large as a standard desktop.e discovery of some "new physics" inside the porous silicon film. Though not fully understood, the scientists speculate that t
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Contact: Robin Goldsmith
rgoldsmi@scripps.edu
(619) 784-8134
Scripps Research Institute
31-Oct-1997