Self-assembly of Intramolecularly Hydrogen-Bonded Amphiphilic Diboronic Acid for Saccharide Recognition

J Colloid Interface Sci. 2019 Mar 1;537:325-332. doi: 10.1016/j.jcis.2018.11.015. Epub 2018 Nov 8.

Abstract

Hypothesis: The designed organic boronic acid molecule featuring both hydrophilic and hydrophobic moieties, makes a potential functional surfactant. Selective recognition of saccharides through morphological changes of phenylboronic acid-based self-assembly system by saccharide stimulation is a key concept in boronic acid design.

Experiments: In the present study, we designed a tuning-fork-shaped amphiphilic diboronic acid (OPAB-C8) which formed vesicular aggregates through self-assembly in aqueous solution and evaluated its saccharide recognition function. The formation of the vesicular aggregates was determined by transmission electron microscopy (TEM) and dynamic light scattering (DLS) measurements. The response of OPAB-C8 to saccharide was measured through ultraviolet-visible (UV-vis) titration experiments.

Findings: The stoichiometric ratio of OPAB-C8 and glucose complex was 1:2, while that of fructose or galactose was 1:1, and OPAB-C8 showed excellent binding affinity to glucose with binding constant was up to 4.6 × 106 M-2. When dealing with glucose, the vesicular aggregates transformed to larger aggregates, whereas the vesicular aggregates disassembled in the presence of fructose. The results revealed that the selective recognition of saccharides through morphological changes was feasible by diboronic acid self-assembled in aqueous solution.

Keywords: Aggregation; Diboronic acid; Functional surfactant; Saccharide recognition; Self-assembly.