The self-healing hydrogels are extremely attractive in biological and biomedical fields. The imine bond obtained by the Schiff base reaction is a commonly used dynamic covalent bond to fabricate self-healing hydrogels. Gelatin is a commonly used natural macromolecule in the biomedical field with excellent biocompatibility, biodegradability, and nonimmunogenicity. However, the gelatin-based hydrogels with self-healing ability are rarely reported based on imine bonds. Herein, we present a facile approach to fabricate a gelatin hydrogel with self-healing ability based on the Schiff base reaction. The gelatin was first reacted with ethylenediamine to increase the content of amino groups. Then dialdehyde carboxymethyl cellulose was used to cross-link amino-gelatin to fabricate the self-healing hydrogel. The results showed that the fabricated hydrogel exhibited good self-healing ability as expected because of the formed dynamic imine bonds between amino-gelatin and dialdehyde carboxymethyl cellulose. The hydrogel also presented good fatigue resistance and self-recovery capacity. Moreover, the self-healing hydrogel possessed ideal hemocompatibility and cytocompatibility. In sum, the fabricated self-healing hydrogel has application prospects in biomedical fields, such as injectable cell and drug carrier and injectable tissue engineering scaffold.

Collagen is a favorable candidate in the field of biomaterials as a wound dressing. However, it cannot be ignored that the application of collagen is limited to its poor physicochemical and perishable properties. It is significant to endow collagen with antibacterial activity and simultaneously improve its physicochemical properties. Here, we present a simple method to fabricate antibacterial collagen-based wound dressing with appropriate physicochemical properties. First, dialdehyde xanthan gum (DXG) was used as an environmentally friendly reducing agent and stabilizer to synthesize silver nanoparticles (AgNPs). Then, collagen/DXG-AgNP composite dressings were fabricated by directly immersing a collagen sponge in the obtained DXG-AgNP aqueous solutions. Our results showed that the spherical AgNPs with diameters of 12–35 nm were successfully synthesized. The presence of DXG effectively prevented aggregation and precipitation of AgNPs in aqueous solution. By the simple one-step solution-immersion approach, AgNPs were homogeneously introduced into the collagen matrix and collagen was simultaneously cross-linked by the existent DXG. Robust antibacterial activity was endowed to collagen as expected while the physicochemical properties of collagen were effectively improved. It is interesting that collagen/DXG-AgNP composite dressings possessed the properties of shape memory, good blood compatibility, and cytocompatibility. In addition, collagen/DXG-AgNP composite dressings could accelerate the deposition of collagen and thereby effectively promote full-thickness burn healing without scar formation.

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The self-healing hydrogel and conductive hydrogel have attracted extensive attention in tissue engineering. The selfhealing hydrogel can restore its original structure and functionality after damage. The conductive hydrogel is beneficial to the differentiation and proliferation of electrical-stimuli-responsive cells. It is significant to integrate the self-healing ability and the electrical conductivity into a single hydrogel system. Herein we present polypyrrole-grafted gelatin-based hydrogels with combined conductive, self-healing and injectable properties. Methacrylic anhydride was first grafted onto gelatin to form double-bond-functionalized gelatin. Then, the commonly used conductive polymer polypyrrole was grafted onto gelatin by reacting with the double bond. Finally, the polypyrrole-grafted gelatin was mixed with ferric ions to construct the hydrogels. As revealed by the results, the hydrogels possess good conductivity owing to the incorporated polypyrrole and ferric ions. The reversible ionic interactions of ferric ions with gelatin and polypyrrole endow the hydrogels with selfhealing abilities. It is interesting that the hydrogels exhibit good injectable properties attributed to their self-healing abilities. Moreover, the hydrogels show a controllable porous structure, an inhibited swelling ability, and good cytocompatibility and blood compatibility.

The porous microstructure of scaffolds is an essential consideration for tissue engineering, which plays an important role for cell adhesion, migration, and proliferation. It is crucial to choose optimum pore sizes of scaffolds for the treatment of various damaged tissues. Therefore, the proper porosity is the significant factor that should be considered when designing tissue scaffolds. Herein, we develop an improved emulsion template method to fabricate gelatinbased scaffolds with controllable pore structure. Gelatin droplets were first prepared by emulsification and then solidified by genipin to prepare gelatin microspheres. The microspheres were used as a template for the fabrication of porous scaffolds, which were gathered and tightened together by dialdehyde amylose. The results showed that emulsification can produce gelatin microspheres with narrow size distribution. The size of gelatin microspheres was easily controlled by adjusting the concentration of gelatin and the speed of mechanical agitation. The gelatin-based scaffolds presented macroporous and interconnected structure. It is interesting that the pore size of scaffolds was directly related to the size of gelatin microspheres, displaying the same trend of change in size. It indicated that the gelatin microspheres can be used as the proper template to fabricate gelatin-based scaffold with a desired pore structure. In addition, the gelatin-based scaffolds possessed good blood compatibility and cytocompatibility. Overall, the gelatin-based scaffolds exhibited great potential in tissue engineering.