Extrusion-based printing of chitosan scaffolds and their in vitro characterization for cartilage tissue engineering

Researchers have looked to cartilage tissue engineering to address the lack of cartilage regenerative capability related to cartilage disease/trauma. For this, a promising approach is extrusion-based three-dimensional (3D) printing technique to deliver cells, biomaterials, and growth factors within a scaffold to the injured site. This paper evaluates the printability of chitosan scaffolds for a cartilage tissue engineering, with a focus on identifying the influence of drying technique implemented before crosslinking on the improvement of chitosan printability. First, the printability of chitosan with concentrations of 8%, 10%, and 12% (w/v) was evaluated and 10% chitosan was selected for further studies. Then, different drying methods, including air drying, warm drying, and vacuum drying followed by crosslinking, were used to study their effect on the mechanical properties of the 10% chitosan scaffolds. Our compression testing results showed the highest elastic modulus for the scaffolds crosslinked with the air-drying technique; as a major part of experiemtn, pore sizes were studies and scaffolds with smaller pore sizes showed higher elastic modulus. Additionally, the geometrical features of scaffolds were examined using a scanning electron microscopy (SEM) technique. The morphology of scaffolds, dried with the aformentioned methods, was assess using SEM images to evaluate the dimensional stability of scaffolds. Chondrocyte cells cultured on the 3D-printed chitosan scaffolds dried using the air-drying technique showed high cell attachment while retaining round cellular morphology. Also, the results of the cytotoxicity test indicated that there was proper biocompatibility of the chitosan for the ATDC5 cells. Results showed that the drying method plays a decisive role in the mechanical and biological behavior of chitosan scaffolds. Considering biological and mechanical properties, the proposed 3D-printed chitosan scaffold can be of a potential structure for cartilage tissue engineering applications.