Publication details

Near-infrared luminescent labels for immunochemical assays and imaging

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Year of publication 2020
Type Conference abstract
MU Faculty or unit

Faculty of Science

Description Fluorescent dyes are widely applied in life sciences and medicine as imaging agents, either alone or conjugated with antibodies or other recognition elements to allow targeting. However, when working with tissues, absorption of visible light and autofluorescence is limiting the use of traditional fluorophores. Therefore, probes working in the far-red and near-infrared (NIR) tissue transparent window are preferred. Among small molecules, polymethine dyes are suitable candidates. Their properties can be tuned by changes in the polymethine chain length and substituents. We chose the indocyanine green (ICG) as an initial model. It is the only NIR fluorophore certified by the FDA for use in clinical medicine. Traditionally, it is used unconjugated as an imaging agent in fluorescence image-guided surgery. Upon coupling with a primary antibody, we have adopted it for specific fluorescent detection of the cancer biomarker CA 19-9. Nanoparticles are an emerging alternative to conventional fluorophores. Despite several limitations, mainly related to their size and toxicity, the photon-upconversion nanoparticles (UCNPs) are particularly attractive. They can convert absorbed NIR light to shorter wavelengths. Thanks to this anti-Stokes emission, the autofluorescence from the sample is eliminated. In comparison to small fluorophores, the surface of the NPs plays a more critical role. Surface modification becomes a necessity but also an opportunity to tune the nanoparticle stability, anti-fouling properties, and biocompatibility. We have applied the BSA- and streptavidin-modified UCNPs as labels in a microtiter plate-based immunoassay for the detection of bacterial honeybee pathogens. Furthermore, surface modification by PEG-neridronate made the UCNPs useful in immunocytochemical staining, which opens the way for their use in more complex biological systems.
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