Ratiometric Quantum Dot Protein Sensors

This thesis focuses on the development of a QD sensor that selectively and ratiometrically responds to the presence of unlabeled proteins. The first investigation generated a model QD-based protein sensor for streptavidin, a bacterial form of an egg white protein. The second studied a QD protein sensor for cyclooxygenase-2, a protein related to inflammation and thus tumor metathesis. A third QD-based protein sensor was developed for thrombin, a protein in the blood coagulation cascade that, in high blood-borne concentrations, is a marker for several diseases. The detection limits of these sensors are in the low pmol/mL range, making them competitive with ELISA assays. These sensors are fast, homogeneous, have detection limits that are scalable with concentration, and are translatable to many other biologically relevant proteins with the use of different small molecular protein binding agents and aptamers. Finally, the synthesis of very bright ZnSe/CdS/ZnS type II QDs is discussed. The unprecedented stability and brightness of these materials allowed for them to be water-solubilized via two different methods. To demonstrate the possibility for sensing applications, an energy-transfer accepting organic dye was conjugated to the water-solubilized type II QDs. Efficient energy transfer was characterized via time-correlated single photon counting; this result ultimately expands the variety of quantum dots that may be used in analytical chemistry.