In situ facile-forming chitosan hydrogels with tunable physicomechanical and tissue adhesive properties by polymer graft architecture

[Display omitted] •Chitosan (Cs) is grafted with PEG with tunable architecture (PEG-g-Cs).•Hydrogel is formed by Schiff base reaction between PEG-g-Cs and PEG-dialdehyde.•PEG graft architecture influences physical interaction with crosslinking polymer.•Hydrogel mechanics are controlled while maintaining facile gelation kinetics.•Potential applications as tissue sealant are examined in ex vivo and in vivo models. In situ forming hydrogels generated upon spontaneous and biocompatible reaction under physiological conditions are widely investigated as injectable and implantable biomaterials. However, it is still a significant challenge to control their mechanics while maintaining their gelation behavior, due to the interdependency between gelation kinetics and mechanics. Herein, physicomechanical properties of in situ forming chitosan hydrogels via Schiff base formation are tuned in a wide range, while maintaining gelation kinetics, via polymer graft architecture. By introducing poly(ethylene glycol) (PEG) grafts with varying lengths and densities, the resulting PEG-grafted chitosan (‘PEG-g-Cs’) not only dissolve readily in neutral aqueous media, but also effectively control the mechanical properties of hydrogels, while maintaining facile gelation kinetics. These properties are further controlled by the chain length of polymeric crosslinker, PEG-dialdehyde. In addition, tissue adhesive properties of the hydrogels are further examined using ex vivo and in vivo models for their potential applications as tissue sealants.