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

Nat Biotechnol. 2001 Jul;19(7):631-5. doi: 10.1038/90228.


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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Biotechnology / methods
  • DNA / metabolism*
  • Fluorescent Dyes*
  • Genetic Techniques*
  • Microscopy, Fluorescence / methods*
  • Nucleic Acid Hybridization / methods*
  • Oligonucleotide Array Sequence Analysis / methods*
  • Oligonucleotides / chemistry
  • Spectrometry, Fluorescence / methods*


  • Fluorescent Dyes
  • Oligonucleotides
  • DNA