Pocket Test Measures Fifty Diagnostic Parameters

The novel device is about the size of a business card and is called the multiplexed volumetric bar-chart chip or V-chip and uses as little as one µL of blood for all the point-of-care- tests.

Scientists at the Methodist Hospital Research Institute (Houston, TX, USA) developed the V-chip, which is composed of two thin pieces of glass that are about 7.6 cm by 5.1 cm. In between are four wells: for hydrogen peroxide; for up to 50 different antibodies to specific proteins, DNA or RNA fragments, or lipids of interest, and the enzyme catalase; for serum or other sample; and for a suitable dye. Initially, the wells are kept separate from each other. A shift in the glass plates brings the wells into contact, creating a contiguous, zigzagged space from one end of the V-chip to the other.

When the substance of interest, such as insulin, binds to antibodies bound to the glass slide, catalase is made active and splits nearby hydrogen peroxide into water and oxygen gas. This approach resembles enzyme-linked immunosorbent assay (ELISA) methods. The oxygen pushes the dye up the column. The more insulin present, the more oxygen is created, and the farther dye is pushed up the slide. Tests show that distance is more or less proportional to the amount of substrate present. The end result is a visual bar chart. The device is easy to read and accurate.

Lidong Qin, PhD, the project's principal investigator, said, "The V-Chip could make it possible to bring tests to the bedside, remote areas, and other types of point-of-care needs. V-Chip is accurate, cheap, and portable. It requires only a drop of a sample, not a vial of blood, and can do 50 different tests in one go. The sensitivity of the V-chip can be improved if narrower and longer bar channels are used. Our next steps are to make the device more user friendly and be so simple to use, it barely needs instructions." The study was published on December 18, 2012, in the journal Nature Communications.

The Methodist Hospital Research Institute