title: A novel homogeneous time-resolved fluoroimmunoassay for carcinoembryonic antigen based on water-soluble quantum dots.
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.
authors.affiliation: School of Biotechnology, Southern Medical University, Guangzhou, 510515, Guangdong, People's Republic of China.
authors.forename: Zhen-Hua
authors.initials: ZH
authors.lastname: Chen
authors.forename: Ying-Song
authors.initials: YS
authors.lastname: Wu
authors.forename: Mei-Jun
authors.initials: MJ
authors.lastname: Chen
authors.forename: Jing-Yuan
authors.initials: JY
authors.lastname: Hou
authors.forename: Zhi-Qi
authors.initials: ZQ
authors.lastname: Ren
authors.forename: Da
authors.initials: D
authors.lastname: Sun
authors.forename: Tian-Cai
authors.initials: TC
authors.lastname: Liu
mesh_terms: D000818:Animals; D002272:Carcinoembryonic Antigen / Q000032:analysis*; D002614:Chelating Agents / Q000737:chemistry; D031541:Fluorescence Resonance Energy Transfer; D005456:Fluorescent Dyes / Q000737:chemistry; D015200:Fluoroimmunoassay / Q000379:methods*; D045663:Quantum Dots; D012995:Solubility; D013725:Terbium / Q000737:chemistry; D013997:Time Factors; D014867:Water / Q000737:chemistry*
chemical_list: D002272:Carcinoembryonic Antigen; D002614:Chelating Agents; D005456:Fluorescent Dyes; D014867:Water; D013725:Terbium