Fig 1: Two types of function are integrated on one chip.

There are several methods for testing blood proteins in hospitals. Some methods involve laboratory testing, large volume blood samples and medical expertise — a time-consuming and costly process that can endanger the lives of heart attack patients. Other methods involve handheld blood testing devices, which are easy to operate and require only finger-prick blood samples. However, the sensitivity of these devices also tends to be much lower.

Fig 1: Two types of function are integrated on one chip: the first function filters blood to extract plasma (bottom left), and the second analyzes the plasma for particular cardiac proteins that indicate heart disorders (top left).

Guo-Jun Zhang and co-workers at the A*STAR Institute of Microelectronics1 have now developed a handheld blood testing device with significantly improved sensitivity. The device has two functions — a blood plasma filter and a silicon nanowire biosensor — integrated onto one chip (see image), and it has the capability to identify protein markers in finger-prick blood samples within 45 minutes.

The integrated chip device developed by Zhang and his team is the first technology of its kind. The test chip is designed to search for three particular cardiac protein biomarkers: troponin T, creatine kinase MM, and creatine kinase MB. If the presence of any of these three biomarkers is detected, it indicates a high risk of heart attack or other heart disorder.

The filter function uses a series of ‘micropillars’ in a carefully designed sequence that acts to separate plasma from the main blood sample. Prior to detection of the biomarkers, all interfering components in the blood need to be removed. This is usually undertaken through the use of lab equipment known as a centrifuge, but Zhang has eliminated the need for this step by integrating the plasma extraction functionality on the chip.

The researchers allowed the blood plasma to flow onto the nanowire biosensor, the surface of which was marked with spots of the three different cardiac protein antibodies. These spots react with the proteins present in the plasma, causing a change in electrical resistance that the researchers could measure. This allows for the detection of biomarkers with good specificity without reducing sensitivity.

The results produced by the new integrated chip device are a marked improvement of up to two orders of magnitude better than current test kits. The researchers are optimistic about the commercial potential of their device, as it uses a simple design that is easy to manufacture. They will continue to develop this technology and undertake clinical trials of the device with industrial partners.