Rapid Whole-Blood Test Uses Gold Nanoshells

A sensitive whole-blood immunoassay is capable of detecting less than one billionth of a gram of the glycoprotein immunoglobulin G (IgG) per milliliter of whole blood and is faster than existing whole-blood immunoassays.

The gold nanoshells are tiny, optically active gold-coated glass particles so small that about 700 could fit in the diameter of a human hair. Because clinicians using existing immunoassays must purify blood before proceeding, the test can require an hour or more. The nanoshell immunoassay is able to overcome this problem by coupling antibodies to nanoshells that absorb near-infrared light.

Since near-infrared light penetrates whole blood very well, it is an optimal wavelength for a whole-blood immunoassay. When the antibody-nanoshell particles are placed into a solution of blood containing the test molecule, the antibody-nanoshells bind to the test molecule, which causes slight changes in the optical properties of the nanoshells. By monitoring these changes, the researchers found they were able to monitor very slight concentrations of antigens in the blood without any sample preparation.

"To our knowledge, this is the first in situ whole-blood immunoassay to report sensitivities on this order in under 30 minutes,” noted Jennifer West, associate professor of bioengineering and chemical engineering at Rice University (Houston, TX, USA) and part of the research team. The study was published in the May 15, 2003, issue of Analytical Chemistry.




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