The detection of biomolecules at the nanoscale is of great significance in fundamental biology research, just as it is for biomedical investigations. The evolution of techniques for the detection and characterization of biomolecules has resulted in remarkable scale and resolution in terms of the size and mass of the molecules. Scientists from Germany have achieved the remarkable feat of pushing the sensitivity limits of interferometric scattering (iSCAT) microscopy, a label-free optical technique for the detection of proteins. The authors accomplish this using an unsupervised machine-learning algorithm and are able to detect proteins with a mass as low as 10 kDa, which is four times smaller than proteins being detected using earlier techniques. The detection and characterization of nanoscale matter are of utmost importance in the understanding of fundamental biological mechanisms involved in physiological processes as well as in diseases.

Using a test that can analyze the patterns of small proteins in blood serum samples in just 30 minutes, researchers were able to differentiate between samples taken from patients diagnosed with cancer and those from patients diagnosed with benign prostate disease. The technique proved effective not only in men with normal and high PSA levels, but also in those whose PSA levels were marginally elevated (4 to 10 nanograms of antigen per milliliter of fluid), in whom it is difficult to rule out cancer without a biopsy. Although the technique is still under evaluation, researchers believe the analysis of protein patterns will be a useful tool in the future for deciding whether men with marginally elevated PSA levels should undergo biopsy. PSA levels are commonly used as a preliminary screen for prostate cancer, but 70 percent to 75 percent of men who undergo biopsy because of an abnormal PSA level do not have cancer. The new proteomic approach has a higher specificity - that is, of the samples the test identifies as cancer, a large percentage are in fact cancer, rather than some other benign disease.