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Abstract
Oxidized sodium alginate is a handily modifiable polysaccharide owing to the pendant aldehyde groups which can form dynamic covalent bonds with amines, acylhydrazines, etc., providing oxidized sodium alginate-based hydrogels with stimuli-responsive properties. However, due to the stiffness and, in particular, the hydrophobicity of sodium alginate dialdehyde at low pH, the mechanical performance and pH stimuli responsiveness of oxidized sodium alginate-based hydrogels are still strictly limited. Herein, we report a new strategy to build an injectable, dual responsive, and self-healing hydrogel based on oxidized sodium alginate and hydrazide-modified poly(ethyleneglycol) (PEG). The hydrazide-modified PEG, referred to as PEG-DTP, acts as a macromolecule crosslinker. We found that the presence of PEG-DTP reduces the hydrophobicity of oxidized sodium alginate at low pH so effectively that even a pH-induced reversible sol-gel transitions can be realized. Meanwhile, the disulfide bonds in PEG-DTP endows the hydrogel with the other reversible sol-gel transitions by redox stimuli. In particular, due to the softness of PEG-DTP chains, mechanical performance was also enhanced significantly. Our results indicate we can easily integrate multi-stimuli responsiveness, injectability, and self-healing behavior together into an oxidized sodium alginate-based hydrogel merely by mixing an oxidized sodium alginate solution with PEG-DTP solution in certain proportions.
Highlights
With high water content and their structural similarity to natural extracellular matrix (ECM), hydrogels have be widely studied and applied in the fields of drug delivery [1], tissue engineering [2], and wound healing [3]
The oxidization of ALG to Aldehyde sodium alginate (ADA) was verified by the FT-IR spectra of sodium alginate (ALG) and oxidized sodium alginate (ADA) (Figure S2), Due to the absorption peak of ADA, a new absorption peak corresponding to the characteristic band of a carbonyl group of ADA
The results indicated indicated that PEG, PEG-DTP, ADA, and hydrogel had good biocompatibility, confirming that the indicated
Summary
With high water content and their structural similarity to natural extracellular matrix (ECM), hydrogels have be widely studied and applied in the fields of drug delivery [1], tissue engineering [2], and wound healing [3]. Especially as the carriers [4] of drugs or cells scaffold [5], hydrogels should incorporate the properties of biocompatibility, injectability, and self-healing. Zhang et al [17] prepared multi-responsive polymer hydrogels based on the dynamic boronate ester and disulfide bonds. The sodium alginate-based hydrogels, can be endowed with stimuli-responsive properties. The dynamic acylhydrazone bonds and disulfide linkages endow the hydrogels with self-healing and stimuli-responsive properties. We synthesized sodium alginate dialdehyde (ADA) and 3,30 -dithiobis (propionohydrazide) (DTP) modified PEG (PEG-DTP) to prepare an injectable, stimuli-responsive, and self-healing hydrogel. The pH-sensitive acylhydrazone bonds and redox-sensitive disulfide linkages endowed the PEG-DTP/ADA hydrogel with dual responsive properties. Because of the outstanding biocompatibility of sodium alginate and PEG, the PEG-DTP/ADA hydrogel was non-cytotoxic, as testified by in vitro cytotoxicity evaluation
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