Meta-Isobutoxy Phenylboronic Acid for Nanoscale Multi-Stimuli-Responsive Low-Molecular-Weight Hydrogelator

Hydrogelators generatehydrogels when dissolved in water, forminga network of interlocking chains on the nanoscale level. For theirunique viscoelastic, mechanical, and swelling properties, these hydrogelshave found various applications, such as water absorbent, biocompatible,and biodegradable scaffolds in tissue engineering and nanocarriersin drug delivery. When measuring the solubility of p-, m-, and o-isobutoxy derivativesof phenylboronic acid, we identified m-isobutoxyphenylboronicacid (PBA) as a low-molecular-weight hydrogelator, the first of whichsolely based on phenylboronic acid. At low concentrations, PBA gelatedwater into a network of cross-linked nanofibers combining amorphousand crystalline phases, as shown by electron and optical microscopy,rheometry, and differential scanning calorimetry and confirmed bysmall- and wide-angle X-ray scattering. By increasing the PBA concentration,we were able to tailor the elastic modulus (G & PRIME;)of PBA hydrogels across 2 orders of magnitude, from 2.5 to 103 kPa.In turn, at a specific PBA concentration, we tuned their viscoelasticproperties by adding urea, thereby adjusting the gelation temperaturebetween 62 and 56 & DEG;C and G & PRIME; at body temperaturebetween 63.4 and 30.4 kPa. Moreover, PBA hydrogels dissolved in responseto various triggers (pH increase, H2O2 and cyclodextrinaddition) and selectively absorbed dyes for liquid mixture separation.These findings demonstrate that PBA has a high potential as a biodegradable,multistimuli-responsive, low-molecular-weight hydrogelator for bioapplications.