Effect of temperature on the photoproperties of luminescent terbium sensors for homogeneous bioassays

Divalent Eu2+ ion - an effective inorganic mediator of energy transfer from the primary chemiluminescence emitter 3 Me2 CHC(H)=O* on Tb3+ and Ru(bpy)3 2+ ions

This study demonstrated for the first time that chemiluminescence (CL) from oxidation of Buⁱ ₂ AlH (Bu = C₄ H₉ ) using oxygen from tetrahydrofuran (THF) was significantly enhanced by the addition of Ru(bpy)₃ ²⁺ . A quantitative comparison of the enhancement efficiency of this CL was performed by addition of ionic phosphors Eu²⁺ , Tb³⁺ and Ru(bpy)₃ ²⁺ . CL enhancement was caused by energy transfer from the primary CL emitter (³ Me₂ CHC(H)=O* aldehyde) to these ionic phosphors. The CL efficiency enhancement was in the order: Eu²⁺ (8.9 × 10⁶ ) > Tb³⁺ (100) > Ru(bpy)₃ ²⁺ (50). The enhanced CL emitters were excited ions: Eu²⁺ *, λ_max  = 465 nm; Tb³⁺ *, λ_max  = 485, 542, 625 nm; and Ru(bpy)₃ ²⁺ *, λ_max  = 567 nm. When two ions Eu²⁺ -Tb³⁺ or Eu²⁺ -Ru(bpy)₃ ²⁺ were present in the reaction solution, the efficiency of CL enhancement by Tb³⁺ or Ru(bpy)₃ ²⁺ ions was much higher, being 1.2 × 10⁶ and 4.2 × 10⁴ , respectively. In this case, two excited ions were simultaneously registered as CL emitters: Eu²⁺ * and Tb³⁺ * or Eu²⁺ * and Ru(bpy)₃ ²⁺ *. Emission intensity of the Eu²⁺ * ion in these emitter doublets is much lower than when only one Eu²⁺ ion is present in solution.

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

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.