Circulating tumour cells (CTCs) are cancer cells that escape from primary tumour sites and enter the bloodstream. This metastasis is responsible for the majority of deaths from cancer. Monitoring the level of CTC levels in blood is thus important but has proved difficult to do. A team of researchers in China and the US has now developed a new way to isolate these cells using a technique called size-amplified acoustofluidics in which the CTCs selectively bind to microbeads.

The bound cancer cells are significantly different in terms of size and physical properties (they are stiffer, for example) compared to normal cells, explain the researchers led by Feng Guo of Indiana University in Bloomington in the US. This means that their acoustic radiation force is a 100-fold higher than that of bare CTCs or normal blood cells. They can thus be efficiently sorted from blood using microbeads (the “size-amplifiers”) in a travelling acoustic wave microfluidic device, and then released from the amplifiers by being degraded with enzymes.

The technique is 77% efficient and produces CTCs with a 96% yield.