Preparation And Self-healing Properties Of Covalently Dynamic Crosslinked Alginate Hydrogels

Partially oxidized alginate(ADA) was preformed by sodium periodate, hydrazide polyethylene glycol was synthesized by PEG and hydrazine hydrate(PEG-DF-1, PEG-DF-2) and Gelatin(Gelatin) as the main components, preparation of produces responsiveness to the environment, at the same time has self-healing properties of hydrogels. According to the different way of crosslinking the experiment was divided into two systems, one system built acylhydrazone bond cross-linked hydrogel point with ADA and PEG-DF-1 as a raw material, the other system with ADA, PEG-DF-2, Gelatin constructed a double crosslinked hydrogel network with hydrazone bond and imide bond.The hydrogel mechanical properties, viscoelastic properties, pH and self-healing response of the two systems were measured. Finally,the cell cytotoxicity of hydrogel in the second system was test.In the first system, it was found the hydrogel not only had sol-gel reversible transition, but also can be achieved spontaneous healing of the incision without heating and addition of a catalyst in the moderate environment. Through self-healing experiments, healed 24 h later,the gel can be restored to 90% of the original gel strength. On the basis of the first system,the mechanical properties of the hydrogel in the second system has been tested.Because of added gelatin as another kind of gel component,in a certain extent, the strength of the gel has been improved,and solved the problem of brittle gel, when the gel was performed with ADA and PEG-DF-2 only. Dynamic viscoelastic test of the second system found that, when the gelatin content increased, the gelling time was significantly shortened. Through the viscoelastic test, when the shear strain increased from 1% to 500%, the storage modulus of the gel reduced by 50%, and intersected with loss modulus of gel gradually, then tanδ≈0.9. When the shear strain recovered to 1%, the storage modulus of the gel has recovered.The molecular force at high strain has been released and the gel has returned to the internal network structure.Finally the toxicity of the second system has been tested. The test result was that when the unreacted aldehyde content was higher, in the extraction process, along with the unreacted oxidizing alginate degradation, dissolution contain more aldehyde substances, cells produced toxic reaction.Dynamic chemically cross-linked hydrogel has been formed, with good mechanical properties, and have self-healing features; through the hydrogel toxicity test, the gel has good cell compatibility in a certain ratio.