Biocompatible Self-Healing Hydrogel for VAT 3D Printing

Self-healing hydrogels (SHHs) are promising materials in tissue engineering due to their ability to mimic the biomechanical properties of biological tissues and autonomously repair damage and can serve as ideal three-dimensional scaffolds for cell proliferation and differentiation. However, conventional processing methods, such as extrusion-based printing, often limit the complexity and resolution of the fabricated structures. VAT photopolymerization, particularly digital light processing (DLP), on the other hand, offers advantages in terms of resolution, printing speed, and design freedom, making it an attractive approach for developing SHHs. This study aims to develop a biocompatible and self-healing hydrogel through DLP, enhancing the structural complexity while maintaining self-repairing properties. The hydrogel is made from polyethylene glycol diacrylate (PEGDA), hydroxyethyl methacrylate (HEMA), dithiothreitol (DTT), and borax, and the solvent is PBS. Cross-linking occurs by radical photopolymerization, in which PEGDA and HEMA serve as cross-linkable monomers, while DTT and borax form borate-ester bonds, imparting self-repairing properties. Complex 3D structures were fabricated by using a commercial DLP printer, and self-healing properties were assessed. Chemical (FTIR, NMR), rheological, and mechanical analyses were performed along with cytocompatibility tests. The hydrogel exhibited successful 3D printability, allowing the fabrication of complex structures. Self-healing tests demonstrated that, after 72 h, the samples could self-repair and withstand tensile forces, maintaining their integrity after multiple damage-repair cycles. Chemical and mechanical characterization confirmed the stability and viscoelastic behavior of the material, while preliminary cytocompatibility assays indicated the suitability for tissue engineering applications. DLP-based printing enables the fabrication of self-healing hydrogels with improved resolution and design freedom. The developed hydrogel exhibits promising mechanical properties and biocompatibility, making it a strong candidate for tissue engineering applications.