A team of US engineers have developed a prototype wearable device that can continuously collect live cancer cells directly from a patient's blood in an advance that could help patients avoid biopsy as well as get treatment for cancer more effectively.Most cancer cells cannot survive in the bloodstream, but those that do are more likely to start a new tumour.Typically, it is these satellite tumours, called metastases, which are deadly, rather than the original tumour. They can release more than 1,000 cancer cells into the bloodstream in a single minute.This means cancer cells captured from blood could provide better information for planning treatments than those from a conventional biopsy, the researchers explained."Nobody wants to have a biopsy. If we could get enough cancer cells from the blood, we could use them to learn about the tumour biology and direct care for the patients. That's the excitement of why we're doing this," said Daniel F. Hayes, Professor at the University of Michigan.The wearable device contains a cell-grabbing chip, which in animal tests trapped 3.5 times as many cancer cells per millilitre of blood as it did running samples collected by blood draw, according to the paper published in the journal Nature Communications.The chip uses nanomaterial graphene oxide to create dense forests of antibody-tipped molecular chains, enabling it to trap more than 80 per cent of the cancer cells in the blood that flows across it.It can also be used to grow the captured cancer cells, producing larger samples for further analysis.The team estimates the device could begin human trials in three to five years. It would be used to help optimise treatments for human cancers by enabling doctors to see if the cancer cells are making the molecules that serve as targets for many newer cancer drugs.