Lab-on-a-chip could speed cancer diagnosis

The lab-on-a-chip works by detecting miniscule membrane vesicles called exosomes, which are found in most cancer cells, Until now, exosomes have been hard to separate out and test because of their small size (between 30 and 150nm). Now, however, a team from the University of Kansas has created a device that promises faster result times, reduced costs, minimal sample demands and better sensitivity of analysis compared to conventional bench-top instruments currently used to examine the tiny biomarkers. The prototype lab-on-a-chip is made of a widely used silicone rubber called polydimethylsiloxane and utilises a technique called on-chip immunoisolation. "We used magnetic beads of 3µm in diameter to pull down the exosomes in plasma samples," said Yong Zeng, an assistant professor of chemistry at the University of Kansas. "In order to avoid other interfering species present in plasma, the bead surface was chemically modified with an antibody that recognises and binds with a specific target protein – for example, a protein receptor – present on the exosome membrane. "The plasma containing magnetic beads then flows through the microchannels on the diagnostic chip in which the beads can be readily collected using a magnet to extract circulating exosomes from the plasma." The device is currently being developed to detect lung cancer, although Zeng says it has the potential to detect different forms of the disease. "Our technique provides a general platform to detecting tumour derived exosomes for cancer diagnosis," he continued. "In addition to lung cancer, we've also tested for ovarian cancer in this work. In theory, it should be applicable to other types of cancer."