A UK research team published a May 27, 2012 paper describing a new technique for finding biomarkers in blood — at a level 9x lower than current techniques. ScienceDaily summarizes the paper as published in Nature Materials. The research team is confident the technique will work for other proteins, and is embarking on work to prove the point.
In plain English, this new science finds PSA at levels far lower (9x) than existing tests. The ScienceDaily summary explains: "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." The abstract puts the point in scientific terms: "We demonstrate the outstanding sensitivity and robustness of this approach by detecting the cancer biomarker prostate-specific antigen down to 10−18 g ml−1 (4 × 10−20 M) in whole serum."
How does the test work ? Thank nanoparticles, in part. "The biosensors used in the new 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, recognises 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."