An implantable cancer sensor that uses a membrane to isolate cancer-detecting nanoparticles should help speed up diagnoses, according to researchers from the US.

Early diagnosis and choosing the right treatment are two of the most important factors in the fight against cancer. One of the best ways to monitor cancer is to look for so-called cancer markers - compounds which are produced by cancerous cells, but until now this has been done by performing blood tests or biopsies.

Michael Cima and colleagues from MIT and Harvard have come up with a way of testing for cancer markers in real-time which could make initial diagnosis quicker, and potentially give an indication of whether a particular treatment is effective.

Nanoparticles whose magnetic properties change in the presence of certain analytes (in this case the cancer markers) have been reported previously, but they have not been used in the body because of their stability and toxicity.

Cima's team solved this by encasing them in a polymer reservoir and semi-isolating them from the environment by using a membrane which only allows small molecules to pass. This allows the cancer markers in (and out) but the nanoparticles remain within the device and are stable. 'We would hope to implant a device at the same time as performing a needle biopsy,' said Cima.

Hsian-Rong Tseng from the University of California, Los Angeles, US, said 'The components of the device are already known to be biocompatible, so this can easily be utilised as an implantable sensor. The multiple wells mean that the measurements can easily be repeated, improving the quality of the data obtained.'

Martin Leach from the Institute of Cancer Research, London, UK, said 'This is indeed an interesting advance; at present the diffusion across the membrane is slow, but if this can be improved, one could envisage truly real-time experiments where it will be possible to observe where and how chemotherapeutics work.'

Cima and his team continue to work closely with clinicians in developing this technology.

Stephen Davey