Antibodies in blood can now be barcoded. So can DNA. Chemists Michael Natan, Christine Keating, and some 20 Penn State inventors have come up with a way to attach microscopic gold- and silver-striped rods to biological molecules. When viewed under blue light, the gold and silver stripes create barcode-like light-and-dark patterns, since silver is much more reflective than gold. Other metals can also be used.

Says Keating, "It's a fundamentally new way to encode information on the submicron scale. The number of distinguishable barcode rods which can, in principle, be prepared is staggering—a pattern for every gene of the human genome is within the realm of possibility."

The rods are made by electroplating metals in narrow channels to form a pattern. They are then coated so that they will bind with the biomolecule being tracked. Rods with different patterns can be attached to many different molecules in the same solution, letting researchers track several biological reactions in very small volumes of fluid.

In one test of the method, for instance, Natan and Keating and their colleagues could distinguish between human and rabbit antibodies in an immunoassay. In another test, the barcodes could locate errors in DNA sequences during a DNA hybridization experiment.

Currently fluorescent dyes are used to tag molecules to monitor such reactions. The nanobarcodes not only offer a wider range of patterns, Keating says, they are more robust. "We have found that the metallic barcode pattern does not degrade even under intense, prolonged illumination."

Christine Keating, Ph.D., is assistant professor of chemistry in the Eberly College of Science, 152 Davey Lab, University Park, PA 16802; 814-863-7832; keating@chem.psu.edu. Michael Natan, Ph.D., a former faculty member, is chief technology officer of SurroMed, Inc., which has licensed the technology. Their research was funded in part by the National Institutes of Health. Reported by Barbara K. Kennedy.