Biomechanical characterization of a fibrinogen–blood hydrogel for human dental pulp regeneration

In dental practice, Regenerative Endodontic Treatment (RET) is applied as an alternative to classical endodontic treatment of immature necrotic teeth. This procedure, also known as dental pulp revitalization, relies on the formation of a blood clot inside the root canal that would lead the formation of a reparative vascularized tissue similar to dental pulp that would give vitality to the affected tooth. Despite the benefit of this technique, it lacks reproducibility due to fast degradation and poor mechanical properties of blood clots. This work presents a method to construct a Fibrinogen-blood hydrogel that mimics viscoelastic properties of human dental pulp preserving the biological properties of blood to be applied in RET. By varying blood and fibrinogen concentrations, gels with different biomechanical and biological properties were obtained. Rheology and atomic force microscopy (AFM) were combined to study viscoelastic properties. AFM was used to evaluate the elasticity of human dental pulp. Degradation and swelling rate were assessed by measuring weight changes. The biomimetic properties of the gels were demonstrated by studying cell survival and proliferation of dental pulp cells (DPSCs) for 14 days. The formation of an extracellular matrix (ECM) was assessed by multiphotonic microscopy (MPM). The angiogenic potential was evaluated by an ex-vivo aortic ring essay, in which the endothelial cells were observed by histological staining after migration. Results show that Fbg-blood gel prepared at 9mg/ml of Fibrinogen and 50% blood of Fbg solution volume, has similar elasticity to human dental pulp and an adequate degradation and swelling rate. It also allows cell survival and ECM secretion and enhances endothelial cell migration and formation of neovessels–like structures.