Researchers at IBM have demonstrated a novel "lab on a chip" that uses capillary action to create a potential one-step diagnostic tool, and which could ultimately test for a wide range of diseases and viruses.
Capillaries in action: The sample collector section of a new microfluidic lab on a chip consists of a network of microscopic channels. Capillary action causes serum from a drop of blood to be drawn into the diagnostic device.The chip requires only a small drop of blood, which it draws through tiny channels within the device. The blood reacts with different disease markers to provide accurate diagnoses in about 15 minutes, says Emmanuel Delamarche, who codeveloped the device at IBM Zurich Research Laboratory in Switzerland.
A nice thing about the new chip is that it involves no moving parts, says IBM's Luc Gervais, who is also a researcher at the University Hospital Basel. Instead, it works using capillary action to filter blood and pump serum through its various chambers.
IBM is an important player in the field of microfluidics, says Jikui Luo, a microfluidics expert at the UK-based Centre for Materials Research and Innovation at the University of Bolton. However capillary driven microfluidic devices are nothing new, he says. "There is a trend toward this sort of moving-part-free device." With no mechanical parts or membranes to pump the fluid, such devices are potentially more reliable, says Luo.
Within its new device, the IBM team has engineered capillary-driven pumps and valves to precisely control the fluid flowing through it. Consumer pregnancy tests use a similar yet simpler approach, says Gervais. But the IBM chip has the potential to test for multiple diseases simultaneously and can give a quantitative response, rather than a simple yes or no, he says. "If a patient has just had a heart attack, a yes or no test is not going to help determine the best course of action," says Gervais. "This [IBM chip] pushes point-of-care diagnostics to the next level."
In their prototype, the IBM researchers created a network of channels, some as narrow as 30 micrometers, with various detection and reaction chambers. As the filtered serum passes through these sections, antibodies embedded within the walls of the channel bind to any disease markers present in the blood. In the case of the prototype, the researchers used a marker commonly used for detecting inflammation and for assessing myocardial damage following heart attacks.
Central deposition zone: Serum passes through a flow resistor (shown as first coil) to control the speed of the blood’s flow, before passing into a zone lined with biomarker-seeking antibodies.In the final stage, these tagged markers are captured by a different set of antibodies, which hold them in place so they can be measured. This is done with a separate device called a fluorescence reader, commonly found in hospitals, which illuminates the chip and measures the amount of fluorescent light given off by the markers. The work is published in the latest issue of the journal Lab on a Chip.
"This work is very interesting," says Juan Santiago, head of the Stanford Microfluidics Laboratory. Not only have the IBM researchers shown that their device can cope with filtering blood, but given the chip's precise control over the liquid, it might also carry out multiple tests in parallel, or even in series of multistage reactions, he says.
IBM is working with Belgian diagnostics firm Coris BioConcept to assess the accuracy of the chips by comparing them directly with traditional laboratory-based testing. "The next step is to develop a pilot series of maybe a thousand devices and test them on samples from hospitals," says Delamarche.
By Duncan Graham-Rowe
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