Google is aiming to diagnose cancers, impending heart attacks or strokes andother diseases, at a much earlier stage than is currently possible. The company is working on technologythat combines disease-detecting nanoparticles, which would enter a patient's bloodstream via a swallowed pill, with a wrist-worn sensor.The idea is to identify slight changes in the person's biochemistry that could act as an early warning system.The work is still at an early stage.Early diagnosis is the key to treating disease. Many cancers, such as pancreatic, are detected only after they have become untreatable and fatal.There are marked differences between cancerous and healthy tissues.Google's ambition is to constantly monitor the blood for the unique traces of cancer, allowing diagnosis long before any physical symptoms appear.The project is being conducted by the search company's research unit, Google X, which is dedicated to investigating potentially revolutionary innovations. It marks the firm's latest shift into the medical sector following its work on glucose-measuring contact lenses for patients with diabetes and the acquisition of a start-up that developeda spoon to counteract the tremors caused by Parkinson's disease.Google has also bought stakes in Calico, an anti-ageing research company, and 23andMe, which offers personal genetic-testing kits Nanoparticles: 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 adiagnosis 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: "Inprinciple 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 thatnow 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 rigorousanalysis" 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 technologybut 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. Theyare prescriptive medical devices, and you know that doctor-patient relationships are pretty privileged and would not involve Google in any way."