Phenylboronate-salicylate ester cross-linked self-healing hydrogel composed of modified hyaluronan at physiological pH.

Several hydrogels with boronate/diol ester cross-linking have been reported. However, multiple synthetic steps or expensive reagents are required to modify some diol moieties into polymers. Therefore, diol-modified polymers, which are easily and inexpensively prepared via a single-step process, are required for the formation of boronate esters. This study reports a novel hydrogel composed of phenylboronic acid-modified hyaluronic acid and salicylic acid-modified hyaluronic acid. This hydrogel is injectable, can self-heal at physiological pH, and can be easily and inexpensively prepared. The polymer system behaved as a sol at pH 12.0 and a weak gel at pH 9.4 and 11.2, whereas it behaved as a gel over a wide pH range of 4.0-8.2. The viscoelasticity of the system decreased in response to sugar at pH 7.3. Thus, salicylic acid can be considered a promising diol moiety for hydrogel formation via boronate ester cross-linking.

Diol or Hydrogen Peroxide-responsive Micellar Systems and Their Rheological Properties.

External stimuli-responsive worm-like micelles (WLMs) have the potential for a wide range of applications. In particular, sugar (a polyol compound)-responsive WLMs have the potential for use in smartdrug release systems. Phenylboronic acid (PBA) functions as a cis-diol sensor in a similar manner it does as a glucose sensor. Thus, WLMs, primarily composed of surfactants and PBA, are expected to function as cis-diol-responsive viscoelastic systems. PBA also reacts irreversibly with hydrogen peroxide (H2O2 ) and is converted into phenol and boric acid. H2O2 is one of reactive oxygen species crucial for several physiological processes. Therefore, H2O2 -responsive WLMs have the potential for various applications. In this review, we describe cis-diol- and H2O2 -responsive micellar systems composed of cetyltrimethylammonium bromide and PBA moieties that shift their viscosities in response to stimuli.