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Near-infrared polymethine fluorophores for targeted biomarker detection

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Year of publication 2021
Type Appeared in Conference without Proceedings
MU Faculty or unit

Faculty of Science

Description Fluorescent dyes are widely used in life-sciences and medicine. They are frequently employed as imaging agents, alone or in connection with antibodies in immunofluorescence experiments. Biological tissues absorb visible light; therefore, a tissue-transparent window (TTW) in the near-infrared (NIR) region is preferred for imaging purposes, e.g. in the fluorescence image-guided surgery. Polymethine dyes are great candidates for applications in the TTW, and their properties can be tuned by changes in the chromophore length and substituents. We chose the indocyanine green (ICG) as an initial model (the only NIR emitting dye certified by FDA for use in clinical medicine). It is usually used as a contrast agent with limited selectivity, but when conjugated to an antibody, it can also be employed for specific visualization of target biomarkers. However, its conjugation is not without pitfalls. The dye inflicted partial aggregation of the antibody during conjugation. Furthermore, we observed a high level of nonspecific binding in a model immunocytochemical labeling of HER2 biomarker on breast cancer cell lines. This was probably caused by the high tendency of the dye to bind to proteins. To overcome this limitation, we conjugated a heptamethine with similar spectral properties, Cyanine 7 (Cy7), to the antibody via Cu-catalyzed click chemistry. The conjugate provided a much higher specificity of labeling, making it a superior NIR dye for immunofluorescence experiments in the TTW.
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