Researchers have created a molecular shield that strengthens the usefulness of near-infrared fluorescent dyes and stabilizes them. Because it can effectively penetrate human flesh, near-infrared light is frequently used in fluorescence bioimaging.
However, the dyes must also be water soluble and carry functional groups for conjugating with targeting biomolecules, such as antibodies or tumor-binding peptides. Fluorescent dyes for this purpose typically have a flat, symmetrical molecular architecture, favoring the absorption of near-infrared light.
Heptamethine cyanines, also known as Cy7, are one of the fluorescent dyes in this family that are being researched for use in surgical procedures. The Cy7 compounds do have some disadvantages, though. Their chromophore absorbs light and is bleached because oxygen radicals can attack it. Additionally, the flat, rigid molecules can group and interact inadvertently with other biomolecules, which would delay the removal of those molecules from the body. The study team improved the dye’s chemical composition to address these problems. They created a thick, clever shield to defend the heptamethine chromophore from oxygen attack.
The center portion of the chromophore was attached to a large aromatic group, and this top group was given long shielding arms that extended over both of the chromophore’s faces, much like a bird covering its nest with its wings.
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