Effect of Cyclodextrins on Saccharide Sensing Function of a Fluorescent Phenylboronic Acid in Water

抄録

An inclusion complex consisting of a fluorescent phenylboronic acid (C1-APB) and β-cyclodextrin (β-CD) acts as a supramolecular saccharide sensor whose response mechanism is based on photoinduced electron transfer (PET). This study evaluated four kinds of cyclodextrins (α-CD, β-CD, γ-CD, and NH₂-β-CD) by comparing their pH profiles, and confirmed that β-CD was the best host for C1-APB because the C1-APB/β-CD complex exhibited high affinity for saccharides as well as high fluorescent recovery upon saccharide binding. An investigation of the β-CD concentration effect revealed the formation of a 1:1 inclusion complex of C1-APB with β-CD. The observed saccharide selectivity of the C1-APB/β-CD complex is in the following order: D-fructose (4039 ± 69 M^-1) > D-ribose (1083 ± 26 M^-1) > L-arabinose (474 ± 11 M^-1) > D-galactose (318 ± 3 M^-1) > maltotoriose (135 ± 5 M^-1) > D-glucose (114 ± 2 M^-1) > maltose (81 ± 2 M^-1). In addition to monomer emission, dimer emission from pyrene dimers was observed in the spectra for the C1-APB/γ-CD complex, which allowed a ratiometric analysis. This study shows that the combination of a simple fluorescent probe, C1-APB, with various CDs diversifies the response systems for saccharide recognition.