Publication details
Single-molecule upconversion-linked digital immunosensing of cancer biomarkers
| Authors | |
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| Year of publication | 2018 |
| Type | Conference abstract |
| MU Faculty or unit | |
| Citation | |
| Description | The ability to detect cancer biomarkers at the single-molecule level promises the ultimate sensitivity in clinical diagnosis. Fluorescence-based single-molecule analysis, however, is limited by matrix interferences, and therefore is typically not suitable for real world analytical applications. This optical background can be elegantly avoided by using photon-upconversion nanoparticles (UCNPs) that emit shorter-wavelength light under near-infrared (NIR) excitation (anti-Stokes emission). Conjugates of UCNPs with antibody can be used as a background-free luminescent tracer in upconversion-linked immunosensing. We have developed an optical approach for visualizing individual UCNPs by conventional epiluminescence microscopy and applied it for the sensitive detection of the cancer biomarker prostate specific antigen (PSA). Individual sandwich immunocomplexes consisting of (1) immobilized anti-PSA antibody, (2) PSA, and (3) anti-PSA antibody-UCNP conjugate were counted under an upconversion wide-field microscope equipped with a 980 nm laser excitation source. The noise-surpassing digital readout provided single particle resolution with almost no instrumental background. This allowed to reach a limit of detection (LOD) of 1.2 pg mL-1 (42 fM) of PSA in 25 % blood serum which is about ten times more sensitive than a classical (analog) readout of luminescence intensity. |
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