Ovarian cancer is the most lethal gynecologic malignancy. This largely reflects the fact that approximately 75% of cases are detected at advanced stages of disease, when cure is unlikely. It is accepted that detecting a greater number of patients with early stage disease by improving screening modalities could significantly improve overall survival. A novel approach to increase the sensitivity and specificity of early detection of cancer is through the application of nanotechnology, where luminescent semiconductor quantum dots (QDs) are conjugated with biomolecules. We developed a prototype of a potential serologic assay with greater sensitivity than current methods permit, using the most widely accepted biomarker for ovarian cancer - CA125. The assay based on immunometric methodology with the use of available quantum dots bioconjugates. The overall schema is: Streptavidin Well -Biotinylated Ab (capture) + Ag(CA 125) + Ab (detector Mab -QD 655 anti-mouse F(ab’)2 conjugate — Read luminescence signal (PL). We used a quantum dot (of wavelength 655 nm) conjugated to goat-F(ab’)2 anti-mouse IgG from Quantum Dots Corporation (Hayward, CA). This fragment was used to label anti-human mouse monoclonal OC 125 antibody to detect CA 125 antigen in plasma samples from patients with cancer. The PL signal from the antigen-antibody complex was measured utilizing high-resolution PL spectroscopy, with confirmation of detected relative level of CA 125 in plasma by reference ELISA. The PL model in our study was developed to identify a spectral signature of QD- bioconjugates. PL spectroscopy was performed in a broad spectral region spanning from 360nm to 1,700nm. We observed that conjugated QDs 655 are reliably detected at substantially reduced concentration, which is critical for defining sensitivity limits of the luminescence metrology. We compared PL from QDs 655 labeled Ab complex and Fab fragments conjugated with Alexa Fluor 647 dye, used previously with Zenon antibody labeling technique. It was noticed that there is a 30% reduction of the luminescent peak half-width and absence of the long-wavelength tail in a case of QD compared to dye. These features are very beneficial to the design of a spectrally resolved spectroscopic assay for cancer detection. Our results show strong concordance of QD 655 assay with reference CA 125 measurement. Titration experiments allowed for optimizing sensitivity of the PL method and developing calibration curves. We explore the specificity of the AB-QDs by comparing ovarian versus other samples (lung cancer) in biomarkers detection. We expect that new assays, based on PL detection of QD- bioconjugates representative of cancer specific biomarker panel, will lead to significant improvements over current strategies for the early detection of cancer.

[Proc Amer Assoc Cancer Res, Volume 46, 2005]