Tuning Room-Temperature Injectability of Gelatin-Based Hydrogels via Introduction of Competitive Hydrogen Bonds

As a natural biomaterial with a superior comprehensive performance, gelatin has been widely explored in various biomedical and bioengineering applications. However, the ease of solidification of gelatin solutions at room temperature causes great inconvenience in specific application scenarios where injection is required. Here we addressed this problem by introduction of competitive hydrogen bond (CHB)-containing substances to gelatin to interfere with the original intergelatin hydrogen bonds. Four representative CHB materials, metformin, l-arginine, polyarginine, and polyurea, all showed remarkable efficiency in tuning the "sol-gel" phase transition temperature of gelatin in a concentration-dependent manner. Systematic rheological measurements indicated that the addition of CHB materials significantly improved the room-temperature injectability of gelatin. Compared to gelatin alone, CHB-containing gelatin bioinks showed improved printability and shape fidelity in 3D bioprinting.