AUTHOR=Gayathry T. C. , Gaur Monika , Mishra Lopamudra , Mishra Monalisa , Barooah Nilotpal , Bhasikuttan Achikanath C. , Mohanty Jyotirmayee 

TITLE=Supramolecular assembly of coumarin 7 with sulfobutylether-β-cyclodextrin for biomolecular applications

JOURNAL=Frontiers in Chemistry

VOLUME=Volume 11 - 2023

YEAR=2023

URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2023.1245518

DOI=10.3389/fchem.2023.1245518

ISSN=2296-2646

ABSTRACT=Coumarins, in general, exhibit a wide range of photophysical characteristics and are highly sensitive to their microenvironment, and therefore, their fluorescence characteristics have attracted immense attention as sensors in chemical and biological systems. In the present study, the supramolecular interaction of a bichromophoric coumarin dye, namely, Coumarin 7 (C7) with sulfobutylether--cyclodextrin (SBE7CD) macrocyclic host at different pH conditions have been investigated by using optical spectroscopic techniques such as absorption, steady-state and timeresolved emission, circular dichroism measurements and compared with that of CD. Considerable enhancement in the fluorescence intensity and lifetime of C7 on complexation with SBE7CD proposes that the non-radiative processes, like TICT behavior is strictly hindered due to the confinement in the host cavity experienced by the C7 dye. The increase in the rotational correlation time evaluated from the fluorescence anisotropy decay kinetics further confirms the formation of tightly bound inclusion complexes. The binding constant values reveal that the monocationic form of dye at pH 3 shows ~3 times stronger interaction with SBE7CD than the neutral form of dye at pH 7 due to strong electrostatic cation-anion interaction. SBE7βCD:C7 exhibits an improved photostability and an upward pKa shift of 0.4 unit as compared to the contrasting downward pKa shift of 0.5 with the CD. The enhanced fluorescence yield and increased photostability have been exploited for the bioimaging applications and better images were captured on staining the Drosophila fly gut with the SBE7βCD:C7 complex. The enhancement in the binding interaction and the emission intensity were found to be responsive to external stimuli such as small competitive binders or metal ions and nearly quantitative dissociation of the complex was demonstrated to release the dye, would find stimuli responsive applications.