Osteokondral Hasarlar İçin Peptit Amfifil ve Bor Katkısı İçeren Gradyan Özellikli Kitosan Biyomürekkep Formülasyonlarının Geliştirilmesi

Abstract

Since the current methods for treating osteochondral damage are insufficient, there is a need to develop new treatment approaches. In this area, research is ongoing to develop alternative treatment methods using tissue engineering approaches, considering the gradient properties of osteochondral tissue that gradually vary between hyaline cartilage and subchondral bone. Among the studies carried out, three-dimensional (3D) bioprinting technology stands out due to its features such as standardization, repeatability, scalability, and the ability to produce tissue scaffolds in predefined sizes and shapes using the patient’s own cells. This doctoral thesis focuses on developing innovative chitosan bioink formulations suitable for use in extrusion-based 3D bioprinting for the production of osteochondral tissue scaffolds with gradient properties. In these formulations, peptide amphiphile (PA) to induce chondrogenic differentiation and boron-doped hydroxyapatite (B-nHAp) to induce osteogenic differentiation were used, and preliminary studies were conducted with MC3T3-E1 pre-osteoblastic cells and umbilical cord mesenchymal stem cells (MSC).

Within the scope of this thesis, characterization studies of B-nHAp and PA, which will be used in the chitosan bioink formulation, were conducted. As a result of the characterization studies, it was concluded that the chitosan bioink formulations containing 10% B-nHAp and 2.5% PA by weight were suitable. The bioink formulations exhibited shear thinning behavior in the range of 0.628-100 rad/s and began to gel at around 25°C. Shear thinning behavior is an indicator of the extrudability of bioinks in 3D bioprinting.

Within the scope of this thesis, osteochondral defects at Grade 4 were targeted, and the production of gradient tissue scaffolds with a thickness of 5 mm was studied. Initially, a flow directing apparatus design was created that can be integrated into the printheads of the 3D bioprinter, and then preliminary studies were conducted to determine the appropriate printing parameters. As a result of the preliminary studies, it was decided to use 20G blunt-end needle nozzle, 60-70 kPa printing pressure, and 4 mm/s printing speed in the experiments. Using the flow directing apparatus, gradient tissue scaffolds with intact pattern geometries were easily produced with a 3D bioprinter using chitosan bioinks containing 10% B-nHAp and 2.5% PA, which were printed into a support solution of 26% Pluronic® F-127 by weight. Characterization studies of the produced gradient tissue scaffolds were conducted, and different structures suitable for bone and cartilage tissues were observed in the layers of the scaffolds.

The results obtained within the scope of this thesis are i) the development of a chitosan-based bioink and ii) the production of osteochondral tissue scaffolds containing a boron-doped nano hydroxyapatite-peptide amphiphile gradient from subchondral bone to hyaline cartilage. These results will contribute to the literature in terms of expanding the variety of bioinks specific to osteochondral tissue.