The new sensor, developed by Mark Reed and colleagues, dispenses with the need to purify blood first and so could be used directly in hospitals without having to send out samples to external laboratories. The sensor can detect nanogram quantities of breast cancer and prostrate cancer markers in just 1 microlitre of whole blood in less than 20 minutes. It might be adapted to work with other physiological fluids and to detect other types of cancer in its early stages.

The sensor combines both purification and detection components in one microfluidic chip. The chip simultaneously captures multiple biomarkers from a sample and releases them, after they have been washed, into a purified buffer where they are sensed by a 25 nm-thick silicon nanoribbon detector. This two-stage analysis isolates the detector part from blood, which is a complex fluid, and therefore reduces the minimum sensitivity required, by effectively "pre-concentrating" the biomarkers.

The biomarkers absorb onto the surface of the nanosensor and produce an electrical signal that can be detected.

The researchers tested their device on two model cancer antigens, PSA and carbohydrate antigen 15.3 – both standard clinical markers for prostrate and breast cancer respectively. Both markers were added to rat blood and the samples allowed to flow through the system.

Previous such sensors did not work because of the high salt concentration of blood. "We combined the nanosensor with a microchip-based filtration system that overcame this problem," Reed told nanotechweb.org.

The team is now working on a number of new applications based on its microchip. "It is an exciting time," he said.

The work was reported in Nature Nanotechnology.