Injectable, strong and bioadhesive catechol-chitosan hydrogels physically crosslinked using sodium bicarbonate

Highlights: • Combining catechol-chitosan and sodium bicarbonate results in strong, bioadhesive and thermosensitive hydrogels. • Optimizing the bicarbonate concentration allows to achieve a high network cohesion and therefore increase bioadhesion. • H IncreIncreasing the extent of catechol grafting creates steric hindrance, which leads to decreased mechanical properties and gelation speed. Fast-gelling chitosan thermosensitive hydrogels have proven to be excellent matrices for targeted drug-delivery and cell therapy. In this work, we demonstrate the possibility of designing injectable bioadhesive hydrogels with a high gelation rate by modifying chitosan with catechol (cat-CH) and using sodium bicarbonate (SHC) as a gelling agent. Cat-CH/SHC hydrogels gel under 5 min at 37 °C and reach a high secant modulus after 24 h (E = 90 kPa at 50% strain). Besides, they show significantly higher adhesion to tissues than chitosan hydrogels thanks to the combination of catechol grafting and physical crosslinking. Their pH and osmolality stayed inside the physiological range. While biocompability tests will be mandatory to conclude regarding their potential for drug or cell encapsulation, these hydrogels uniquely combine physiological compatibility, injectability, fast gelation, good cohesion, and bioadhesion.