Photophysical characterization and BSA interaction of the direct ring carboxy functionalized unsymmetrical NIR cyanine dyes

type:Journal Article
Novel near infrared (NIR) sensitive unsymmetrical cyanine dyes bearing direct –COOH functionalized indole ring were synthesized, characterized and subjected to photophysical investigations. These unsymmetrical cyanine dyes were then subjected to investigate their interaction with bovine serum albumin (BSA) as a model protein in Phosphate buffer solutions. Apart from NIR absorption and emission with high molar extinction coefficients they exhibit a blue shift in PBS solution owing to their enhanced dye aggregation. Interaction of these dyes with BSA leads to not only enhanced emission intensity but also bathochromically shifted absorption maximum due to formation of dye-BSA conjugate. These dyes bind strongly with BSA having about an order of magnitude higher binding constant as compared to the typical cyanine dyes. Amongst the unsymmetrical cyanine dyes investigated in this work one bearing substituents like Iodo and carboxylic acid in the terminal Indole rings (UCD-3) exhibited highest association with the BSA having very high binding constant of 1.01 × 107 M−1.
source:https://doi.org/10.1016/j.dyepig.2017.01.015