Figure 2

Enzyme-biomarker triggered, highly sensitive fluorophore/GNP complex. The complex normally emits little fluorescence because the SS places the fluorophore close to the GNP for fluorescence quenching. When the complex is placed in an environment with the enzyme biomarker, SS is cleaved by the enzyme and the distance between the fluorophore and GNP becomes to the length of LL, resulting in the fluorescence emission at an enhanced level. In this illustration, to simplify the concept, only a set of SS and LL for the GNP are shown. In reality, multiple SS/LL-fluorophore sets are to bind to a single GNP.