Peptidomimetic Modified Heptamethine Cyanine Dyes for Enhanced Bioimaging Targetability: A Molecular Interaction Study on Bovine Serum Albumin and Human Parvalbumin

Cyanine dyes have found great applications in bioimaging due to their NIR-emitting capabilities. In this work, six heptamethine cyanine dyes (TEA1-6) were designed, synthesized, and photophysically studied. While they had strong absorption, their fluorescence was quenched in aqueous solutions. The dyes incorporated amide linkages and amino acid moieties, intended to mimic the peptide bonds to potentially improve biological interactions. This hypothesis was tested by examining the potential interactions between the dyes and two common biological proteins, bovine serum albumin (BSA) and human parvalbumin (HPA). Interestingly, the dyes' nonfluorescent behavior in aqueous solutions was reversed upon the addition of the proteins BSA or HPA. This was hypothesized to be due to the binding interactions with these proteins and the disruption of the aggregates formed in aqueous solutions. These findings showed that peptide-like substituents could help promote protein recognition and open the horizon for more implementation in biomedical applications.