Most diseases involve the increased or decreased production of specific proteins, but these molecules are so hard to detect that using them as biomarkers for clinical diagnosis of disease has been very limited. Being able to spot target proteins can significantly expand the capabilities of hospital labs and lead to early detection and treatment of cancer and all kinds of other diseases
Now researchers at Brooklyn’s Polytechnic Institute of New York University (NYU-Poly) have created the first label-free system capable of detecting single protein molecules, including biomarkers for cancer and other diseases that are much smaller than any viruses. So far they demonstrated the technique on two proteins, including thyroglobulin, a human cancer biomarker, and believe the technology will be able to detect considerably smaller proteins.
In 2012, Arnold and his team were able to detect in solution the smallest known RNA virus, MS2, with a mass of 6 attograms. Now, with experimental work by postdoctoral fellow Venkata Dantham and former student David Keng, two proteins have been detected: a human cancer marker protein called Thyroglobulin, with a mass of just 1 attogram, and the bovine form of a common plasma protein, serum albumin, with a far smaller mass of 0.11 attogram. “An attogram is a millionth of a millionth of a millionth of a gram,” said Arnold, “and we believe that our new limit of detection may be smaller than 0.01 attogram.”
This latest milestone builds on a technique pioneered by Arnold and collaborators from NYU-Poly and Fordham University. In 2012, the researchers set the first sizing record by treating a novel biosensor with plasmonic gold nano-receptors, enhancing the electric field of the sensor and allowing even the smallest shifts in resonant frequency to be detected.
Letter in Nano Letters: Label-Free Detection of Single Protein Using a Nanoplasmonic-Photonic Hybrid Microcavity