Use of Luminescent CdSe–ZnS Nanocrystal Bioconjugates in Quantum Dot-Based Nanosensors

Biomolecules labeled with luminescent colloidal semiconductor quantum dots (QDs) have potential for use in numerous applications, including fluoro-immunoassays and biological imaging. QD labels exhibit size-tunable narrow-band luminescent emission and high resistance to photodegradation. They also exhibit efficient Förster energy transfer between neighboring QDs of different sizes and their emission is readily quenched by bound fluorescent dyes. In this paper, we describe preliminary results aimed at defining conditions for the design and preparation of nanoscale QD-bioconjugate sensors based on fluorescence quenching. We envision building sensor assemblies that employ quantum dots linked with dye-labeled biological receptors that utilize donor–acceptor energy transfer between QDs and receptors for conducting recognition-based assays. In particular, we report the effects of varying the concentration of energy acceptors bound to nanocrystal surfaces under both soluble and solid phase conditions on quenching phenomena.