Photon-upconversion nanoparticles for single-molecule immunoassays
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| Year of publication | 2021 |
| Type | Conference abstract |
| MU Faculty or unit | |
| Citation | |
| Description | The recent progress in the field of immunoassays has been enabled by the development of various kinds of nanomaterials. In particular, photon-upconversion nanoparticles (UCNPs) proved to be excellent labels due to their ability to emit shorter wavelength light under near-infrared excitation (anti-Stokes emission), which prevents autofluorescence, minimizes light scattering, and thus reduces the optical background. These unique properties enabled imaging of single UCNPs by wide-field epiluminescence microscopy and allowed development of single-molecule (digital) immunoassays. We have synthesized conjugates of polyethylene glycol-coated UCNPs with streptavidin and applied them as a label for the detection of cancer biomarker prostate specific antigen (PSA). The detection was based on counting of individual sandwich immunocomplexes under the wide-field microscope. The noise-surpassing digital readout (particle counting) resulted in 20× higher sensitivity than the analog readout (output light intensity) and provided a detection limit of 23 fg mL-1 (800 aM) in 25% human serum. The conjugates of UCNPs with streptavidin are also useful as a label for the detection of bacterial pathogens. We have developed an immunoassay for the detection of causative agent of European foulbrood, bacterium Melissococcus plutonius. The assay provided a limit of detection of 340 CFU mL-1 and its practical applicability was verified by the analysis of real samples of bees, larvae and bottom hive debris. |
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