Recent progress in 3D bioprinting technologies has shown promising results for the multi-material design of interface tissue engineering. However, the achievement of structural integrity between tissues with different mechanical strengths is a great challenge in the bio-fabrication of tissue interfaces, such as bone-cartilage interfaces1. In this study, we used multimaterial 3D bioprinting approach for the deposition of hydrogel structures based on an aspiration-on-demand capillary method. The obtained construct showed a high degree of structural integrity at the interface between adjacent ink segments mimicking the bone-cartilage tissue interface. To do so, specific amounts of different cell-laden hydrogels were extruded in the same capillary and deposited at the desired geometrical pattern2. The ink segments, comprised of Alginate (Alg)/Gelatin (Gel), and Carboxymethylcellulose (CMC)/ Gelatin for soft and hard tissue, respectively. The inks were prepared as the following: Alg and CMC were dissolved in PBS separately by forming amide bonds by carbodiimide-mediated precipitation of material's carboxyl groups with Tyramine's amino groups utilizing EDC/NHS reaction. Therefore, a specified amount of tyramine and NHS were applied to the CMC and Alg mixture followed by adding EDC was added to the NHS at an equal molar ratio to make Alg-Ph and CMC-Ph. Two polymer mixtures were stirred for 24 h, dialyzed against deionized water, and were lyophilized for 3 days. Gelatin was added at 15% w/v in PBS and incubated for 1 day at 37 °C to acquire Gel-Alg-Ph and Gel-CMC-Ph. The hydrogels were crosslinked at the presence of ruthenium (Ru) mixture and sodium persulfate (SPS) photo-initiating system under a visible light source at the concentration of 0.1/1 Ru/SPS (mM/mM). Mesenchymal stem cells (MSCs) were grown and added to the two ink mixtures in various cell counts for the targeted tissue. Mechanical properties of the casted samples were assessed with different parameters such as various Alg-Ph, CMC-Ph, Ru/SPS concentrations, and the visible light exposure time. Differentiation of MSC cells expected after 21 days, histology, immunohistochemistry, and a live/dead test for the bioprinted structure were carried out. [ASF1] The outcomes of the in vitro biochemical studies were corroborated by the result of the histological staining. This research, which investigated the multilayered and hierarchical architecture of osteochondral tissue using 3D biofabricated material compositions, could lead to an improved regeneration of osteochondral lesions in the future.
1. Diloksumpan, P. et al. Biofabrication 12, (2020).
2. Nadernezhad, A. et al. Sci. Rep. 6, 1–12 (2016).