Nano particles applied in early detecting cancers

The diagnostic project is being led by Dr Andrew Conrad, a molecular biologist who previously developed a cheap HIV test that has become widely used.

"What we are trying to do is change medicine from reactive and transactional to proactive and preventative," he told the BBC.

"Nanoparticles... give you the ability to explore the body at a molecular and cellular level."

Google is designing a suite of nanoparticles which are intended to match markers for different conditions.

They could be tailored to stick to a cancerous cell or a fragment of cancerous DNA.

Or they could find evidence of fatty plaques about to break free from the lining of blood vessels. These can cause a heart attack or stroke if they stop the flow of blood.

Another set would constantly monitor chemicals in the blood.

High levels of potassium are linked to kidney disease. Google believes it will be possible to construct porous nanoparticles that alter colour as potassium passes through.

"Then [you can] recall those nanoparticles to a single location - because they are magnetic - and that location is the superficial vasculature of the wrist, [where] you can ask them what they saw," said Dr Conrad.

Unattached nanoparticles would move differently in a magnetic field from those clumped around a cancer cell.

In theory, software could then provide a diagnosis by studying their movements.

As part of the project, the researchers have also explored ways of using magnetism to concentrate the nanoparticles temporarily in a single area.

The tech company's ambition is ultimately to create a wristband that would take readings of the nanoparticles via light and radio waves one or more times a day.

Prof Paul Workman, chief executive of the Institute of Cancer Research in London, told the BBC News website: "In principle this is great. Any newcomers with new ideas are welcome in the field.

"There is an urgent need for this. If we can detect cancer or other diseases earlier, then we can intervene with either lifestyle changes or treatment.

"How much of this proposal is dream versus reality is impossible to tell because it is a fascinating concept that now needs to be converted to practice."

His team at the institute is investigating cancer cells and cancer DNA in the blood as new methods of diagnosis and planning treatment.

He did warn Google that a diagnosis could increase anxiety and lead to unnecessary treatment, so there needed to be "very careful and rigorous analysis" before this type of blood monitoring could be used widely.

The scheme is being made public because Google is now seeking to establish partnerships.

But Dr Conrad sought to play down the idea that his firm wanted to run a search tool for the human body, alongside the one it already offers for the internet.

"We are the inventors of the technology but we have no intentions of commercialising it or monetising it in that way," he said.

"We will license it out and the partners will take it forward to doctors and patients.

"These are not consumer devices. They are prescriptive medical devices, and you know that doctor-patient relationships are pretty privileged and would not involve Google in any way."

Analysis: James Gallagher, health editor

From searching the internet to searching your blood, Google certainly has high ambitions. But is it feasible?

The basic principles are sound and mirror the work already taking place around the world.

Many research groups are looking at bits of cancer floating in the blood as a better way of diagnosing the disease and also to assess which tumours are more aggressive.

But Google will have to address concerns around "false positives", when healthy people are told they are ill.