Biological response of 3D-printedß-tricalcium phosphate bioceramic scaffolds with the hollow tube structure.

It is a large clinical challenge to repair critical-size bone defects, and vascularization in the early stage is of vital importance in bone regeneration. In recent years, 3D-printed bioceramic is a kind of common bioactive scaffold for repairing bone defects. However, conventional 3D-printed bioceramic scaffolds consist of stacked solid struts with low porosity, which limits the ability of angiogenesis and bone regeneration. The hollow tube structure can induce endothelial cells to build the vascular system. In this study,ß-tricalcium phosphate (ß-TCP) bioceramic scaffolds containing the hollow tube structure were prepared with digital light processing-based 3D printing strategy. The physicochemical properties and osteogenic activities of prepared scaffolds could be precisely controlled by adjusting the parameters of hollow tubes. Compared with solid bioceramic scaffolds, such scaffolds could significantly improve the proliferation and attachment activity of rabbit bone mesenchymal stem cellsin vitro, and facilitate early angiogenesis and subsequent osteogenesisin vivo. Therefore,ß-TCP bioceramic scaffolds with the hollow tube structure possess great potential application for the treatment of critical-size bone defects.

3D printing of conch-like scaffolds for guiding cell migration and directional bone growth.

Regeneration of severe bone defects remains an enormous challenge in clinic. Developing regenerative scaffolds to directionally guide bone growth is a potential strategy to overcome this hurdle. Conch, an interesting creature widely spreading in ocean, has tough spiral shell that can continuously grow along the spiral direction. Herein, inspired by the physiological features of conches, a conch-like (CL) scaffold based on ß-TCP bioceramic material was successfully prepared for guiding directional bone growth via digital light processing (DLP)-based 3D printing. Benefiting from the spiral structure, the CL scaffolds significantly improved cell adhesion, proliferation and osteogenic differentiation in vitro compared to the conventional 3D scaffolds. Particularly, the spiral structure in the scaffolds could efficiently induce cells to migrate from the bottom to the top of the scaffolds, which was like "cells climbing stairs". Furthermore, the capability of guiding directional bone growth for the CL scaffolds was demonstrated by a special half-embedded femoral defects model in rabbits. The new bone tissue could consecutively grow into the protruded part of the scaffolds along the spiral cavities. This work provides a promising strategy to construct biomimetic biomaterials for guiding directional bone tissue growth, which offers a new treatment concept for severe bone defects, and even limb regeneration.