Tannic Acid as a Degradable Mucoadhesive Compound

To achieve site-specific delivery of pharmaceuticals, the development of effective mucoadhesive polymers is essential. Thus far, only a few polymers, such as thiolated ones and related variants, have been studied. However, their mucoadhesiveness varies depending on the type of polymer and the degree of chemical functionalization. Furthermore, the chemistry of tethering often requires harsh reaction conditions. Recently, pyrogallol-containing molecules have emerged as good tissue and hemostatic adhesives, but their in vivo mucoadhesive properties have not been demonstrated. Herein, we found that pyrogallol-rich tannic acid (TA) formulated with poly­(ethylene glycol) (PEG), named TAPE, exhibits superior mucoadhesive properties. TAPE is prepared by a simple physical mixture of TA and PEG. It remained on esophageal mucus layers for at least several hours (<8 h) after oral feeding. The mucoadhesion originated from intermolecular interaction between the polyphenols of TA and mucin, exhibiting pH dependency. TAPE adhered strongly to mucin in neutral conditions but bound weakly in acidic conditions due to different hydrolysis rates of the ester linkages in TA. Thus, TAPE might be useful as a long-lasting esophageal mucoadhesive composite

Dynamic Bonds between Boronic Acid and Alginate: Hydrogels with Stretchable, Self-Healing, Stimuli-Responsive, Remoldable, and Adhesive Properties

For the increasing demand of soft materials with wide ranges of applications, hydrogels have been developed exhibiting variety of functions (e.g., stretchable, self-healing, stimuli-responsive, and etc.). So far, add-in components such as inorganic nanoparticles, carbon materials, clays, and many others to main polymers have been used to achieve various unique functions of hydrogels. The multicomponent hydrogel systems often exhibit batch-dependent inconsistent results and problems in multicomponent mixings, require labors during preparations, and accompany unpredictable cross-talk between the added components. Here, we developed ‘single polymeric component’, alginate-boronic acid (alginate-BA) hydrogel to overcome the aforementioned problems. It exhibits unprecedented multifunctionalities simultaneously, such as high stretchability, self-healing, shear-thinning, pH- and glucose-sensitivities, adhesive properties, and reshaping properties. Multifunctionalities of alginate-BA hydrogel is resulted from the reversible inter- and intramolecular interactions by dynamic equilibrium of boronic acid–diol complexation and dissociation, which was proved by single molecule level Atomic Force Microscopy (AFM) pulling experiments. We also found that the alginate-BA gel showed enhanced in vivo retentions along gastrointestinal (GI) tract. Our findings suggest that rational polymer designs can result in minimizing the number of a participating component for multifunctional hydrogels, instead of increasing complexity by adding various additional components