Quantum-dot-tagged microbeads for multiplexed optical coding of biomolecules

Abstract

Multicolor optical coding for biological assays has been achieved by embedding different-sized quantum dots (zinc sulfide-capped cadmium selenide nanocrystals) into polymeric microbeads at precisely controlled ratios. Their novel optical properties (e.g., size-tunable emission and simultaneous excitation) render these highly luminescent quantum dots (QDs) ideal fluorophores for wavelength-and-intensity multiplexing. The use of 10 intensity levels and 6 colors could theoretically code one million nucleic acid or protein sequences. Imaging and spectroscopic measurements indicate that the QD-tagged beads are highly uniform and reproducible, yielding bead identification accuracies as high as 99.99% under favorable conditions. DNA hybridization studies demonstrate that the coding and target signals can be simultaneously read at the single-bead level. This spectral coding technology is expected to open new opportunities in gene expression studies, high-throughput screening, and medical diagnostics.

In vivo quantum dot labeling of mammalian stem and progenitor cells

“…QDs have significant advantages compared with traditional organic fluorophores, including size-tunable emission, increased quantum efficiency, broader absorption spectra, narrower emission spectra (i.e., smaller full-width half-maximum), and remarkable resistance to photo bleaching (Bruchez et al, 1998;Chan and Nie, 1998;Han et al, 2001;Rieger et al, 2005). QDs may also be superior to conventional fluorophores in fluorescence resonance energy transfer (FRET) experiments, where there is transfer of energy from a donor to an acceptor fluorophore.…”

Development of a Functionalized Xenon Biosensor

“…The Xe NMR signal demonstrated a response to Implementation of high-sensitivity fluorescence-based systems in a direct multiplexing assay is challenging due to spectral overlap, despite the high wavelength tunability of some systems such as quantum-dot-tagged microbeads. 52,53 In microarray format, realization of the xenon biosensor could result in a high density assay in which each well of the microtiter plate would not contain individual interacting pairs, but rather a single synthetic product interacting with a complete set of derivatized target molecules. Within each well, binding to different targets would be distinguishable on the basis of chemical shift.…”

Aqueous phase synthesis of CdTe quantum dots for biophotonics

“…More importantly, surface modification of QDs can be applied to conjugate biomolecules (e.g. DNA, antibodies or proteins) to the QD surface to achieve selective targeting [20][21][22][23]. For instance, bioconjugated QDs have been used in cell labeling, tissue imaging, photosensitization for photodynamic therapy, in vivo tumor detection, and drug delivery [24][25][26][27].…”