Task 1.1 Optimization of the hydrogel composition and 3D-printed titanium lattice deposition method:
This task focused on optimizing both the composition of the self-assembling peptide-polysaccharide hydrogel and its integration within 3D-printed titanium implants. Three main incorporation strategies were evaluated to achieve homogeneous and stable hybrid scaffolds:
1. In situ gelation within the 3D printed titanium lattice, which yielded continuous, self-supporting hydrogel filling of the titanium lattice.
2. Lyophilization of the gel following in situ gelation, which resulted in a dry, easy-to-store and handle scaffold that filled the titanium implants and covered the implant surface.
Both approaches were identified as effective and were therefore selected for subsequent in vivo evaluation.
3. Injection of pre-formed hydrogel into the porous implant, which allowed partial filling but resulted in lower homogeneity and mechanical stability; this method was therefore not pursued further.
Additionally, we performed enzymatic degradation assays to assess the stability of the hyaluronic acid component in the presence of hyaluronidase, both with and without the FmocFF peptide fibrillary mesh. These experiments provided valuable insight into the stabilizing effect of the peptide-polysaccharide interaction and improved the optimization process. Moreover, short-term stability and reproducibility of the optimized formulation were confirmed.
Task 1.2 In vivo evaluation of bio-active 3D-printed titanium lattice in critical-size bone defect and biocompatibility analysis:
In this task, the bioactive 3D printed titanium lattice developed in Task 1.1 was evaluated in vivo in a rabbit calvarial critical-size defect model. Defects of 8 mm in diameter, were created in the calvaria of adult New Zealand White rabbits. The defects were treated with either (i) an inert titanium implant (control), (ii) a hydrogel-integrated implant, or (iii) a lyophilized-scaffold integrated implant. The surgical procedure and postoperative course proceeded without complications, and all animals recovered uneventfully. After eight weeks of healing, bone regeneration was assessed using micro-computed tomography (microCT) and histological analyses.
Both the hydrogel- and lyophilized scaffold-integrated titanium implants significantly enhanced bone regeneration and bone-implant integration, compared to the inert control, in a substantial and biologically meaningful manner. The hydrogel-integrated implant, in particular, demonstrated a marked enhancement of bone formation in the inner region of the 3D-printed titanium lattice, where regeneration is typically most challenging, highlighting the effectiveness of the bioactive hydrogel approach.
