'Barcode chip' developed for cheap, fast blood tests

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London, Nov 26 : Getting a blood test done would soon become cheap and matter of minutes, all thanks to a new "barcode chip" developed by researchers at the California Institute of Technology (Caltech).

A person only needs less than 10 minutes with just a pinprick's worth of blood, and the chip can measure the concentrations of dozens of proteins, including those that herald the presence of diseases like cancer and heart disease, its creators claim.

Called the Integrated Blood-Barcode Chip, or IBBC, the device was developed by a group of Caltech researchers led by James R. Heath, the Elizabeth W. Gilloon Professor and professor of chemistry. An IBBC, is about the size of a microscope slide and is made out of a glass substrate covered with silicone rubber. The chip's surface is moulded to contain a microfluidics circuit--a system of microscopic channels through which the pinprick of blood is introduced, protein-rich blood plasma is separated from whole blood, and a panel of protein biomarkers is measured from the plasma. The chip offers a significant improvement over the cost and speed of standard laboratory tests to analyse proteins in the blood.

In traditional tests, one or more vials of blood are removed from a patient's arm and taken to a laboratory, where the blood is centrifuged to separate whole blood cells from the plasma. The plasma is then assayed for specific proteins.

"We wanted to dramatically lower the cost of such measurements, by orders of magnitude. We measure many proteins for the cost of one. Furthermore, if you reduce the time it takes for the test, the test is cheaper, since time is money. With our barcode chip, we can go from pinprick to results in less than 10 minutes," Nature quoted him as saying.

A single chip can simultaneously test the blood from eight patients, and each test measures many proteins at once.

"We are aiming to measure 100 proteins per fingerprick within a year or so. It's a pretty enabling technology," said Heath.

In order 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," which 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 study, 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," said Heath.

The barcode chip was also used to analyse the blood of breast and prostate cancer patients for a number of proteins that serve as biomarkers for disease.

The proteins can also change as a patient receives therapy. Thus, determining these biomarker profiles can allow doctors to create individualized treatment plans for their patients and improve outcomes.

The ease and the speed with which results can be obtained using the IBBC also will potentially allow doctors to assess their patients' responses to drugs and to monitor how those responses evolve with time.

"As personalized medicine develops, measurements of large panels of protein biomarkers are going to become important, but they are also going to have to be done very cheaply. It is our hope that these IBBCs will enable such inexpensive and multiplexed measurements," said Heath.

The study is described in a paper in the advance online edition of Nature Biotechnology.

ANI

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