May 30, 2012
Super-sensitive tests could detect diseases earlier
(Ivanhoe Newswire) — Disease detectives at their best! Scientists have developed an ultra-sensitive test that should enable them to detect signs of a disease in its earliest stages.
The test designed by scientists from Imperial College London and the University of Vigo detect particular molecules that indicate the presence of disease, even when these are in very low concentrations.
While, there are already tests available for some diseases that look for such biomarkers using biological sensors or 'biosensors', existing biosensors become less sensitive and predictable at detecting biomarkers when they are in very low concentrations, as occurs when a disease is in its early stages.
The team demonstrated that the new biosensor test can find a biomarker associated with prostate cancer, called Prostate Specific Antigen (PSA). They tested 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 team detected PSA at 0.000000000000000001 grams per millilitre, which is at the limits of current biosensor performance. By comparison, an existing test called an Enzyme-Linked Immunosorbent Assay (ELISA) test can detect PSA at 0.000000001 grams per millilitre, which is nine orders of magnitude more concentrated.
"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," Steven was quoted saying.
The biosensors used in the 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.
The new test could enable more reliable diagnosis, but more research will need to be done to further explore its potential. The next stage of the research will see the team carrying out further clinical testing to assess the efficacy of the biosensor in detecting a range of different biomarkers associated with conditions such as HIV and other infections.
Source: Nature Materials, May 2012