Self-healing injectable stimuli responsive polysaccharide hydrogel constructed with dynamic covalent bonds

Hydrogels based on dynamic covalent bonds have unique properties and are competent in many biomedical fields. However, critical issues such as biocompatibility, mechanical properties, and stimulus responsiveness are required to be solved. It is also expected to develop a simple preparation method with mild conditions. Based on these objectives, chitosan (CS), sodium alginate (SA) and 2-formylphenylboronic acid (2-FPBA) are used to prepare the dynamic covalent bond hydrogels within minutes neither chemical medications nor severe conditions. Benefiting from the imine borate and boronic ester bonds both formed in the hydrogels, the hydrogels are stable, injectable, and of efficient self-healing properties. The damage-recovery process can be repeated for more than 6 cycles. The microstructure of the hydrogels recoded by atomic force microscopy (AFM) is consistent with the mechanical properties and both of them could be affected by the concentrations of SA and 2-FPBA. Moreover, the dynamic hydrogels are responsive to pH values and oxidative environment. When the model drug 5-fluorouracil (5-FU) is loaded in the dynamic hydrogels, the release profiles are sustainable and present significant differences with various stimuli. These dynamic covalent bond hydrogels have a promising prospect in tissue engineering and drug delivery.