“It is very important to detect proteins without the use of fluorescent labeling,” says Luke Lee, director of the Biomolecular Nanotechnology Center at University of California, Berkeley, who was not directly involved in the research. Fluorescent labeling is complex and prone to bleaching or fading, which can throw off the signal.

The research has established the technology’s potential to detect low concentrations of proteins in a mere attoliter of blood. While such sensitivity is not critical for identifying a risk of blood clotting, it is important in monitoring for other diseases. Scientists could record measurements in different cellular organelles–separate compartments within the cell–rather than averaged over the whole cell. “It is remarkable accomplishment that they are able to detect the protein at such low concentrations,” says Lee.

“You could actually locate in a cell what is happening at a particular time point in a viral infection,” says Michael Ochsenkühn a chemist at University of Edinburgh and one of the researchers on the project. Currently the Edinburgh scientists are using the same technology to look at the biomolecular interactions involved in autoimmune disease. They are also investigating host-pathogen interactions for viral research.

Campbell’s team had previously shown that the gold nanoshells appear safe when injected into cells–they don’t cause cell death or impede new cell growth. As gold is unreactive, the body will not reject the implant, say the researchers. But the technology still has a number of hurdles to overcome before it can be used for medical applications.

“The limit of such research is, it needs an aptamer that catches a specific protein,” says Jaebum Choo an analytical chemist at Hanyang University in Korea, who was not involved in the study. “While the thrombin aptamers are well known, few known aptamers for other proteins are known at this stage. For the development of this technology, biologists and biochemists need to find the various different kinds of aptamer for capturing valuable proteins.”