The use of nanomaterials, specifically fluorescent semiconductor quantum dots (QDs), for biological imaging and sensing has become very topical. Here we present a historical synopsis of research in this field to help elucidate the origins of the most recent advances in QD-based technology. We further aim to educate the novice researcher concerning many important aspects of QD synthesis, water-solubilization, functionalization, and usage in biological imaging and sensing that are generally not discussed in the literature. We will also summarize several recent transformative examples of using quantum dots for in vitro and in vivo studies.

No abstract

We have created a platform for the ratiometric fluorescent sensing of targeted proteins by conjugating conjoined protein binding agent/organic dye ligands to water-soluble, emissive semiconductor quantum dots (QDs). The QD emission is tuned such that it may serve as an energy transfer donor to the dye acceptor. Upon exposure to the target proteins, these analytes bind to the surfaces of the QDs and change the microenvironments of the QD-bound dyes such that the emissive properties of the dyes are perturbed. The resulting alteration in the QD and dye fluorescence spectra creates a readout that is fully quantitative. The advantage of our methodology is that the detection of proteins is very fast as the platform is fully homogeneous, whereas the heterogeneous ELISA assay involves multiple steps with blocking agents and secondary reporters that ultimately complicate the process. The calculated detection limits for the two QD protein-sensing examples reported here are also competitive with the ubiquitous ELISA assay.

A one-step method to produce ≈12 nm hydrodynamic diameter water-soluble CdSe/ZnS quantum dots (QDs), as well as CdS/ZnS, ZnSe/ZnMnS/ZnS, AgInS2 /ZnS, and CuInS2 /ZnS QDs, by ligand exchange with a near-monolayer of organosilane caps is reported. The method cross-links the surface-bound silane ligands such that the samples are stable on the order of months under ambient conditions. Furthermore, the samples may retain a high quantum yield (60%) over this time. Several methods to functionalize aqueous QD dispersions with proteins and fluorescent dyes have been developed with reaction yields as high as 97%.

No abstract