A single chip can simultaneously test the blood from eight patients, and each test measures many proteins at once. The researchers reported on devices that could measure a dozen proteins from a fingerprick of blood, and their current assays are designed for significantly more proteins. "We are aiming to measure 100 proteins per fingerprick within a year or so. It's a pretty enabling technology," Heath says.
To perform the assay, a drop of blood is added to the IBBC's inlet, and then a slight pressure is applied, which forces the blood through a channel. As the blood flows, plasma is skimmed into narrow channels that branch off from the main channel. This part of the chip is designed as if it were a network of resistors, which optimizes plasma separation.
The plasma then flows across the "barcodes." The barcodes consist of a series of lines, each 20 micrometers across and patterned with a different antibody that allows it to capture a specific protein from the plasma passing over. When the barcode is "developed," the individual bars emit a red fluorescent glow, whose brightness depends upon the amount of protein captured.
In the Nature Biotechnology paper, the researchers used the chip to measure variations in the concentration of human chorionic gonadotropin (hCG), the hormone produced during pregnancy. "The concentration of this protein increases by about 100,000-fold as a woman goes through the pregnancy cycle, and we wanted to show that we could capture that whole concentration range through a single test," Heath says.
The scientists also used the barcode chip to analyze the blood of breast and prostate cancer patients for a number of proteins that serve as biomarkers for disease. The types and concentrations of the proteins vary from disease to
|Contact: Kathy Svitil|
California Institute of Technology