A novel homogeneous time-resolved fluoroimmunoassay for carcinoembryonic antigen based on water-soluble quantum dots

J Fluoresc. 2013 Jul;23(4):649-57. doi: 10.1007/s10895-013-1175-0. Epub 2013 Mar 8.

Abstract

Quantum dots are not widely used in clinical diagnosis. However, the homogeneous time-resolved fluorescence assay possesses many advantages over current methods for the detection of carcinoembryonic antigen (CEA), a primary marker for many cancers and diseases. Therefore, a novel luminescent terbium chelates- (LTCs) and quantum dots-based homogeneous time-resolved fluorescence assay was developed to detect CEA. Glutathione-capped quantum dots (QDs) were prepared from oil-soluble QDs with a 565 nm emission peak. Conjugates (QDs-6 F11) were prepared with QDs and anti-CEA monoclonal antibody. LTCs were prepared and conjugates (LTCs-S001) were prepared with another anti-CEA monoclonal antibody. The fluorescence lifetime of QDs was optimized for sequential analysis. The Förster distance (R0) was calculated as 61.9 Å based on the overlap of the spectra of QDs-6 F11 and LTCs-S001. Using a double-antibody sandwich approach, the above antibody conjugates were used as energy acceptor and donor, respectively. The signals from QDs were collected in time-resolved mode and analyzed for the detection of CEA. The results show that the QDs were suitable for time-resolved fluoroassays. The spatial distance of the donor-acceptor pair was calculated to be 61.9 Å. The signals from QDs were proportional to CEA concentration. The standard curve was LogY = 2.75566 + 0.94457 LogX (R = 0.998) using the fluorescence counts (Y) of QDs and the concentrations of CEA (X). The calculated sensitivity was 0.4 ng/mL. The results indicate that water-soluble QDs are suitable for the homogenous immunoassay. This work has expanded future applications of QDs in homogeneous clinical bioassays. Furthermore, a QDs-based homogeneous multiplex immunoassay will be investigated as a biomarker for infectious diseases in future research.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Carcinoembryonic Antigen / analysis*
  • Chelating Agents / chemistry
  • Fluorescence Resonance Energy Transfer
  • Fluorescent Dyes / chemistry
  • Fluoroimmunoassay / methods*
  • Quantum Dots*
  • Solubility
  • Terbium / chemistry
  • Time Factors
  • Water / chemistry*

Substances

  • Carcinoembryonic Antigen
  • Chelating Agents
  • Fluorescent Dyes
  • Water
  • Terbium