Abstract
Luminescent semiconductor nanocrystals or quantum dots (QDs) are a recentlydeveloped class of nanomaterial whose unique photophysical properties are helping tocreate a new generation of robust fluorescent biosensors. QD properties of interest forbiosensing include high quantum yields, broad absorption spectra coupled to narrow sizetunablephotoluminescent emissions and exceptional resistance to both photobleaching andchemical degradation. In this review, we examine the progress in adapting QDs for severalpredominantly in vitro biosensing applications including use in immunoassays, asgeneralized probes, in nucleic acid detection and fluorescence resonance energy transfer(FRET) - based sensing. We also describe several important considerations when workingwith QDs mainly centered on the choice of material(s) and appropriate strategies forattaching biomolecules to the QDs.
Highlights
The most common method of detecting and quantitating biomolecules still remains the use of fluorescence [1,2]
Many of the organic dye and protein-based fluorophores currently in use do, suffer from serious chemical and photophysical liabilities. These include pH dependence, self-quenching at high concentrations, susceptibility to photo-bleaching, short-term aqueous stability, narrow absorption windows coupled to broad red-tailed emission spectra via small Stokes shifts, and short excited state fluorescent lifetimes [1,2]. This has resulted in the synthesis of a vast library of fluorophores, many of which are geared towards very specific applications; for example the staining of cellular mitochondria organelles with MitoTracker dyes or using tetramethylrhodamine for resonance energy transfer quenching of a proximal fluorescein donor in a Taqman-based nucleic acid assay [1,4]
Since their first description in a biological context [5,6], colloidal luminescent semiconductor nanocrystals or quantum dots (QDs) have elicited a great deal of interest in the biosensing community due to their unique fluorescent properties. These fluorescent properties may overcome some of the liabilities of conventional organic and protein-based fluorophores to help create a new generation of robust biosensors
Summary
The most common method of detecting and quantitating biomolecules still remains the use of fluorescence [1,2]. These include pH dependence, self-quenching at high concentrations, susceptibility to photo-bleaching, short-term aqueous stability, narrow absorption windows coupled to broad red-tailed emission spectra via small Stokes shifts, and short excited state fluorescent lifetimes [1,2] Over time, this has resulted in the synthesis of a vast library of fluorophores, many of which are geared towards very specific applications; for example the staining of cellular mitochondria organelles with MitoTracker dyes or using tetramethylrhodamine for resonance energy transfer quenching of a proximal fluorescein donor in a Taqman-based nucleic acid assay [1,4]. We provide an overview of several important considerations when working with QDs including choice of material, capping ligand, effect of overall size, and the available methods for biofunctionalization
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