Mussel-Inspired Hydrogel Composite with Multi-Stimuli Responsive Behavior

A mussel-inspired adhesive hydrogel with pH, temperature, and near-infrared (NIR) light-responsive behavior is designed. The hydrogel system is formulated by combining chitosan modified with catechol motifs, thermo-responsive poly(N-isopropylacrylamide) terminated with catechols, and light-absorbing polypyrrole nanoparticles (PpyNPs). The effects of catechol concentration, molar ratio of Fe3+ to catechol units, pH, and the incorporation of the PpyNPs on the mechanical property of the formed hydrogel are investigated. The responsive behaviors of the resulting hydrogel composite to pH, temperature, and NIR light are also demonstrated. The obtained hydrogel also shows promising adhesive property to glass and steel substrates. It is anticipated that the fabricated adhesive hydrogel with multi-responsive behavior, especially NIR light response, can potentially be useful in a wide range of biomedical applications, such as remotely controlled release systems and removable sealant materials.