Gold has been used in medicine since 2500 BC, as a drug and in medical devices, but since the 1980s, it's gained a starring role in diagnostics. In a paper in Nature Materials, its latest incarnation is as gold nanostars helping to create a very sensitive biomarker-driven biosensor for spotting disease in its very early stages.
Prostate-specific antigen (PSA) is a known biomarker for prostate cancer, and the levels begin to rise in patients whose cancer is recurring. If this biomarker could be detected at very low levels, which current tests cannot do, this could allow treatment to begin much earlier. The team, from Imperial College London and the University of Vigo in Spain, used PSA as a proof of concept to test the biosensor, and it was able to detect PSA at levels ninefold lower than existing tests.
The biosensor uses nanoparticle-sized gold stars coated with antibodies to PSA, and a second enzyme-linked anti-PSA antibody. The gold stars link to the PSA, and then the second antibody connects, creating a silver nanocrystal coating that can be seen under a microscope. This technology amplifies the very small signal.
Professor Molly Stevens, senior author of the study from the Departments of Materials and Bioengineering at Imperial College London, said: "It is vital to detect diseases at an early stage if we want people to have the best possible outcomes--diseases are usually easier to treat at this stage, and early diagnosis can give us the chance to halt a disease before symptoms worsen. However, for many diseases, using current technology to look for early signs of disease can be like finding the proverbial needle in a haystack. Our new test can actually find that needle. We only looked at the biomarker for one disease in this study, but we're confident that the test can be adapted to identify many other diseases at an early stage."
Prostate cancer is a key target, as it causes between a quarter and a third of the cancer deaths in men in the U.S. This project focused on PSA, but the biosensor has potential for a wide range of other known biomarkers--it could also be used to find traces of contaminants in food or the environment, or signs of infectious disease. The researchers are planning clinical studies with the biosensor with other biomarkers, including HIV and other infections.