Photon-upconversion nanoparticles as a background-free label in immunosensing and bioimaging

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Authors

FARKA Zdeněk MICKERT Matthias Jürgen HLAVÁČEK Antonín GORRIS Hans-Heiner SKLÁDAL Petr

Year of publication 2021
Type Conference abstract
MU Faculty or unit

Faculty of Science

Citation
Description Fluorescence-based detection is very popular readout method in immunosensing and cell imaging. However, it is limited by autofluorescence and light scattering of the surrounding matrix. This optical background can be elegantly avoided by using photon-upconversion nanoparticles (UCNPs), which emit shorter-wavelength light under near-infrared excitation (anti-Stokes emission). Bioconjugates of UCNPs can be used as a background-free luminescent label in upconversion-linked immunosensing. We have synthesized conjugates of UCNPs with streptavidin based on copper-free click chemistry and coating of the UCNPs by bovine serum albumin, which reduces the level of non-specific binding. The conjugates were employed in sandwich detection of bacterium Melissococcus plutonius, the causative agent of honeybee disease of European foulbrood. The assay provided a limit of detection of 340 CFU/mL, which is 400 times better than conventional ELISA. The practical applicability was verified by the analysis of real samples of honeybees, larvae and bottom hive debris. The conjugates of UCNPs can also serve as labels in cell imaging. We have employed PEG-based conjugates for staining of HER2 biomarker on breast cancer cells. Due to the low optical background as well as low non-specific binding, the UCNP conjugates provided superior signal-to-background ratio (S/B = 319) compared to the fluorescence-based experiment with the identical immunoreagents (S/B = 6).
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