Support-less ceramic 3D printing of bioceramic structures using a hydrogel bath.

Volumetric bone tissue defects are difficult to address with intrinsic regenerative capacity. With the recent development of ceramic 3D printing, various types of bioceramic scaffolds that can induce bone regeneration are being actively developed. However, hierarchical bone is complex with overhanging structures that are unfavorable to ceramic 3D printing, requiring additional sacrificial supports that may increase the overall process time and material consumption. Additionally, breaks and cracks may occur when sacrificial supports are removed from fabricated ceramic structures. In this study, a support-less ceramic printing (SLCP) process using a hydrogel bath was developed to facilitate the manufacturing of complex bone substitutes. A hydrogel bath, consisting of Pluronic P123 with temperature-sensitive properties, mechanically supported the fabricated structure when the bioceramic ink was extruded into the bath and promoted the cement reaction to cure the bioceramic. SLCP enables the fabrication of complex bone constructs with overhanging structures that cannot be fabricated without sacrificial supports, such as the mandible and maxillofacial bones, with reduced overall processing time and material consumption. Scaffolds fabricated with SLCP showed more cell adhesion, higher cell growth rate, and osteogenic protein expression due to their rougher surface than conventionally printed scaffolds. Hybrid scaffolds were fabricated with SLCP to co-print cells and bioceramics, and SLCP provided a cell-friendly environment, exhibiting high cell viability. SLCP enables control of the shape of various cells, bioactive substances, and bioceramics, which can be used as an innovative 3D bioprinting technique to manufacture complex hierarchical bone structures.