Sugar-responsive smart materials based on phenylboronic acid and cyclodextrin

Abstract

This review focuses on sugar-responsive materials based on phenylboronic acid (PBA) as a sugar-sensing motif and cyclodextrins (CyDs) as a basic skeleton of smart materials. PBA modified α-CyD (PBA-α-CyD) forms a supramolecular polymer through intermolecular interactions between PBA part and CyD cavity. Similarly, PBA-β-CyD forms a head-to-head dimer. Meanwhile, combining PBA-γ-CyD and polyethylene glycol (PEG) produces a molecular necklace. Additionally, combining PBA-modified PEG and native α-CyD or γ-CyD results in another type of molecular necklace. These supramolecular structures are obtained as powders, and their solubility increases in the presence of sugar. Besides the powder type, a unique gel is formed through crosslinking polyvinyl alcohol with PBA-triazole-γ-CyD (PBA-Tri-γ-CyD). This gel can contain model drug, and it shows sugar-responsive drug release. The sugar response of all of these smart materials can be explained by the concept of equilibrium. The smart materials are constructed with CyD-guest interactions. The CyD-guest equilibrium moves by a reaction between sugar and PBA moiety attached to the smart material. In these smart materials, sugar induces a dissociation in the CyD-guest interaction, and this dissociation results in sugar-induced disintegration of CyD-guest supramolecular structures.