The Simoa limit of detection is typically about a factor of 100 to 1000 times more sensitive than the traditional method of performing a protein assay—the enzyme-linked immunosorbent assay (ELISA) technique. It opens up the potential for being able to measure proteins at concentrations that have never been detected before in various kinds of samples including blood, which is the main focus for Simoa-based assays. However, we still cannot detect certain proteins when measuring blood samples because the Simoa technology does not give us the sensitivity that we need to measure some of the molecules present in the blood at lower expression levels. Currently, we are attempting to push the boundary of sensitivity to detect even lower concentrations using nanotechnology. Nanomaterials modified with enzymes or DNA are utilized for signal amplification to further improve the sensitive of digital ELISA.
Catalytic Activity of Single Nanoparticles
Metal nanoparticles are important catalysts in a variety of industrial applications. However, their catalytic properties are not fully understood, as they are highly dependent on the details of particle structure, including shape, size, composition, and crystallinity. Using a method analogous to that described for single molecule enzyme activities, we can explore the individual catalytic activities of a heterogeneous ensemble of nanoparticles. The system chosen for this study is the oxidation of Amplex Red by hydrogen peroxide to form the fluorescent product resorufin, catalyzed by gold nanoparticles. The catalytic activities of the individual nanoparticles, as well as the detailed kinetics of the reactions, are being measured and statistically analyzed. These catalytic properties will be correlated with the optical and structural properties of the nanoparticles, via optical spectroscopy and scanning electron microscopy, respectively.