Research at Massachusetts General Hospital has led to a microchip that can quickly sort through elusive circulating tumor cells (CTC’s) found within the blood of cancer patients.
The existence of CTCs has been known since the mid-19th century, but since they are so hard to find, it has not been possible to adequately investigate their biology and significance. Microchip-based technologies have the ability to accurately sense and sort specific types of cells, but have only been used with microliter-sized fluid samples, the amount of blood in a fingerprick. Since CTCs are so rare, detecting them in useful quantities requires analyzing samples that are 1,000 to 10,000 times larger.
To meet that challenge the MGH BioMEMS Resource Center research team – led by Mehmet Toner, PhD, senior author of the Nature report and director of the center in the MGH Department of Surgery, and Ronald Tompkins, MD, ScD, chief of the MGH Burns Unit and a co-author – first investigated the factors required for microchip analysis of sufficiently large blood samples. The device they developed utilizes a business-card-sized silicon chip, covered with almost 80,000 microscopic posts coated with an antibody to a protein expressed on most solid tumors. The researchers also needed to calculate the correct speed and force with which the blood sample should pass through the chip to allow CTCs to adhere to the microposts.
“We developed a counterintuitive approach, using a tiny chip with critical geometric features smaller than a human hair to process large volumes of blood in a very gentle and uniform manner – almost like putting a ‘hose’ through a microchip,” explains Toner.
Mass General press release: Microchip-based device can detect rare tumor cells in bloodstream …
Abstract in Nature: Isolation of rare circulating tumour cells in cancer patients by microchip technology … Nature 450, 1235-1239 (20 December 2007)