Paper detail

Synthesis, characterization, and biological evaluation of gelatin-based scaffolds

This thesis presents the development of entropy-elastic gelatin based networks in the form of films or scaffolds. The materials have good prospects for biomedical applications, especially in the context of bone regeneration. Entropy-elastic gelatin based hydrogel films with varying crosslinking densities were prepared with tailored mechanical properties. Gelatin was covalently crosslinked in water above its sol gel transition, which suppressed the gelatin chain helicity. Amorphous films were prepared with tailorable degrees of swelling and wet state Young's modulus. The knowledge gained with this bulk material was transferred to the integrated process of foaming and crosslinking to obtain porous gelatin-based scaffolds. A gelatin solution was foamed in the presence of saponin and the resulting foam was fixed by chemical crosslinking with a diisocyanate. The scaffolds were analyzed in the dry state by micro computed tomography (μCT, porosity: 65\pm 11-73\pm 14 vol.-%), and scanning electron microscopy (SEM, pore size: 117\pm 28-166 \pm 32 μm). After equilibration with water, the scaffolds were form-stable and displayed shape recovery after removal of mechanical loads. The composition dependent compression moduli (Ec: 10 50 kPa) were comparable to the bulk micromechanical Young's moduli, which were measured by atomic force microscopy (AFM). The hydrolytic degradation profile could be adjusted, and a controlled decrease of mechanical properties was observed. The scaffold cytotoxicity and immunologic responses were analyzed in vitro. Indirect eluate tests were carried out with L929 cells so that fully cytocompatible scaffolds were obtained. Furthermore, the material immune response was investigated in vitro. Minimal material endotoxin contamination was successfully achieved (<0.5 EU/mL) by using low-endotoxin gelatin and performing all synthetic steps in cleanroom.