A novel process was developed to fabricate core/shell-structured 3D scaffolds, made of calcium-deficient hydroxyapatite (CDHA) and alginate laden with pre-osteoblast MC3T3-E1 cells, through a combination of cement chemistry, dual paste-extruding deposition (PED), and cell printing. The cement reaction of calcium phosphates replaced the typical sintering process of the ceramic scaffold fabrication after the simultaneous printing of the ceramics and cell-laden hydrogel. The alginate crosslinking process was divided into two steps using different concentrations of CaCl₂, during and after 3D printing, in order to obtain a stable 3D core/shell structure and high cell viability. The whole process was carried out under conditions (neutral pH and a temperature between room temperature and 37 °C) that were gentle to the cells, so the cells incorporated into the shell remained alive throughout the 3D scaffold for the entire culture period (35 days). The core/shell structured scaffold significantly enhanced the mechanical properties when compared with a hydrogel that uses a typical cell-printing process or with a ceramic scaffold, due to the co-operative effect of each material. The compressive strength of the CDHA/alginate scaffolds in the wet state was 3.2 MPa, whereas the compressive strength of alginate could not be determined in the wet state. The 3D structural morphology of CDHA/alginate scaffolds was well retained, even after a compression test, and showed less deformation because the CDHA ceramic-core was encapsulated within the elastic alginate. The process developed in this study suggests a new cell printing model that has excellent potential for application in the field of bone tissue regeneration.

Coronavirus disease 2019 (COVID-19), which has recently emerged as a global pandemic, has caused a serious economic crisis due to the social disconnection and physical distancing in human society. To rapidly respond to the emergence of new diseases, a reliable in vitro model needs to be established expeditiously for the identification of appropriate therapeutic agents. Such models can be of great help in validating the pathological behavior of pathogens and therapeutic agents. Recently, in vitro models representing human organs and tissues and biological functions have been developed based on high-precision 3D bioprinting. In this paper, we delineate an in-depth assessment of the recently developed 3D bioprinting technology and bioinks. In particular, we discuss the latest achievements and future aspects of the use of 3D bioprinting for in vitro modeling.

Ceramic 3D printing based on stereolithography is an excellent alternative to overcome drawbacks of conventional subtractive manufacturing for 3D shape control. Optimization of photocurable ceramic slurry is one of the most essential conditions to achieve favorable 3D printed structures using SL. Homogeneity of ceramic particle dispersion in photocurable resin is particularly important to optimize ceramic suspension. Dispersant plays a significant role in increasing homogeneity. Dispersant in photocurable ceramic resin has an additional effect on photocurability and integrity of 3D printed green body. We herein discuss how dispersants influence 3D printing conditions based on stereolithography using various commercially available dispersants of BYK series such as BYK103, BYK111, BYK180, BYK182, and BYK2001. Both BYK111 and BYK180 showed better performances than others because of their lower volatilities under general temperature condition during a printing process. Both solubility and decomposition temperature of dispersants largely influenced the structural quality after washing and debinding processes. This study provides worthy information to design photocurable ceramic suspension for various types of ceramic materials.