A new miniaturized biomedical “lab-on-a-chip” testing device for exosomes — molecular messengers between cells — promises faster, earlier, less-invasive diagnosis of cancer, according to its developers at the University of Kansas Medical Center and the University of Kansas Cancer Center. “A lab-on-a-chip shrinks the pipettes, test tubes and analysis instruments of a modern chemistry lab onto a microchip-sized wafer,” explained Yong Zeng, assistant professor of chemistry at the University of Kansas. Zeng and his fellow researchers developed the lab-on-a-chip initially for early detection of lung cancer — the number-one cancer killer in the U.S. Lung cancer is currently detected mostly with an invasive biopsy, after tumors are larger than 3 centimeters in diameter and even metastatic. Using the lab-on-a-chip, lung cancer could be detected much earlier, using only a small drop of a patient’s blood, according to Zeng.
The prototype lab-on-a-chip is made of a widely used silicone rubber called polydimethylsiloxane and uses a technique called “on-chip immunoisolation.” “We used magnetic beads of 3 micrometers in diameter to pull down the exosomes in plasma samples,” Zeng said. “To avoid other interfering species present in plasma, the bead surface was chemically modified with an antibody that recognizes 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.”