An ultrasensitive test has been developed that should enable scientists to detect signs of a disease in its earliest stages.

The test created is able detect particular molecules that indicate the presence of disease, even when these are in very low concentrations.

Scientists from the Imperial College London (UK) collaborating with the University of Vigo (Spain) demonstrated that the new biosensor test can find a biomarker associated with prostate cancer, called Prostate Specific Antigen (PSA). The team demonstrated the effectiveness of their biosensor by testing PSA biomarker samples in solutions containing a complex mixture of blood derived serum proteins.

Monitoring the levels of PSA at ultralow concentrations can be crucial in the early diagnosis of the reoccurrence of prostate cancer, but classic detection approaches are not sensitive enough to carry out this analysis with a high degree of accuracy. The new test could enable more reliable diagnosis, but more work will need to be done to further explore its potential.

The biosensors used in this study consist of nanoscopic-sized gold stars floating in a solution containing other blood-derived proteins. Attached to the surface of these gold stars are antibodies, which latch onto PSA when they detect it in a sample. A secondary antibody, which has an enzyme called glucose oxidase attached to it, recognizes the PSA and creates a distinctive silver crystal coating on the gold stars, which is more apparent when the PSA biomarkers are in low concentrations. This silver coating acts like a signal that PSA is present, and it can be easily detected by scientists using optical microscopes.

In their study, the team detected PSA at 10-18 g/mL, which is at the limits of current biosensor performance. By comparison, an existing test called an enzyme-linked immunosorbent assay (ELISA) that can detect PSA at 10-9 g/mL, which is nine orders of magnitude more concentrated. The team says that the biosensor can be easily reconfigured to test for other diseases or viruses where the related biomarker is known.

Molly M. Stevens, PhD, the senior author of the study and a professor 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. 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." The study was published on May 27 2012, in the journal Nature Materials.

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Imperial College London
University of Vigo