Abstract Summary/Description
Near-infrared (NIR) cyanine dyes are an interesting class of fluorophores due to their unique optical properties and tunable structure which can be manipulated to obtain fluorophores optimized for different applications. One of the sites of modifications is the central meso position which can be modified using the Smiles rearrangement to attach different heteroatoms to the conjugated system. A specific form of Smiles Rearrangement was used in this project that includes an electrophile integration which allowed the formation of a quaternary ammonium center, leading to the formation of highly positively charged fluorophores. Two sets of fluorophores were synthesized in the same scheme; the first one was obtained from the meso modification of heptamethine dyes using 2-(Methylamino)ethanol, and the other one was obtained by using the Smiles rearrangement on the meso-modified fluorophores. The first set showed metal sensing ability toward copper (II) ions and not to other metal cations. The second set, characterized by having a quaternary ammonium center, are highly positively charged and are promising candidates for bioimaging of the cartilage. Our lab has developed cartilage-specific fluorophores that showed excellent cartilage targeting but a very expensive synthetic pathway due to the use of thiocholine. Using the Smiles rearrangement will allow the formation of fluorophores of similar cartilage targeting ability, but in a much more economical synthesis. This optimization approach not only allowed the formation of two sets of fluorophores with different and beneficial applications but also opened the horizon for additional optimizations towards more biomedical applications.
