Three-Dimensional Printing of Scaffolds with Synergistic Effects of Micro–Nano Surfaces and Hollow Channels for Bone Regeneration

Abstract

The 3D printing technology with unique strategies for accurate fabrication of biomaterials in regenerative medicine has been widely applied in bone regeneration. However, the traditional 3D printing scaffolds are only stacked by solid struts without any hollow channel structures, which limits the new bone tissue formation. In this study, a special 3D scaffold with hollow channels and a micro–nano surface was prepared by a modified 3D printing strategy combined with the hydrothermal treatment approach. By regulating the reaction solution of hydrothermal treatment, the micro–nano structures formed on the surface of scaffolds can be successfully controlled. Moreover, the scaffolds have the ability to facilitate the attachment and proliferation of BMSCs after culturing for 1, 3, and 7 days in vitro. Interestingly, the in vivo results demonstrated that the hollow channels and the micro–nano surface present synergistic effects on bone regeneration. They both boost the new bone formation in femur defects in rabbits for 12 weeks after operation. The study demonstrates a 3D scaffold with special surface microstructures and hollow struts that can overcome the shortages of most traditional scaffolds and meanwhile improve the bioactivity of biomaterials for bone tissue engineering.

Vascularization in tissue engineering: The architecture cues of pores in scaffolds

“…Additionally, the micro-nano surface and hollow channels showed synergistic effects for bone formation in vivo. 96 Although the effects of the structures on vessel formation were not investigated in this study, the importance of the micro/nano surface and the macro pores for cells response and tissue formation was confirmed.…”

How Does Scaffold Porosity Conduct Bone Tissue Regeneration?

“…In another report, although hydrothermally-treated akermanite hollow structure showed a porosity of (72.9%), which was almost comparable to that of the akermanite hollow structure (72.8%); however, it showed higher bone formation (Figure 4g,h). [177] In one report, the brick-mortar architecture of nacre was the inspiration to fabricate a porous composite scaffold in which higher new bone formation and integration was observed. This is likely due to the lamellar microstructure of akermanite.…”

“…Reproduced with permission. [74,75,133,145,177,207] an apatite layer may alter the pore size and morphology of the scaffold and in turn reduce the pore size and pore interconnectivity as well as the amounts of micropores in the struts (pore walls). [184] It is thought that the growth of apatite crystal in the inner pore wall may fill out the small pores, reduce the pore size, and enhance the compressive strength of a scaffold.…”

“…[142] However, a study reported that the generation of microstructures and nanostructures on the surface of scaffolds increase the porosity, and this leads to a significant decrease in compressive strength. [177] An assured approach to deal with the growth of cracks is coating. A polymeric coating can bridge the cracks, [59,118,128] fill out the crack-like defect in the struts, [141] and densify the struts and clog pores in scaffolds.…”

Nanotechnologies and Nanomaterials in 3D (Bio)printing toward Bone Regeneration

“…Feng et al recently prepared silicate‐based bioceramic akermanite scaffolds by combining the hollow channels with the micro/nanosurface features utilizing an extrusion‐based 3D printing strategy with modified nozzles and hydrothermal treatment. [ 125 ] The micro/nanotopological structures could be successfully controlled on the 3D‐printed Fe scaffold surface by adjusting the reaction solution of hydrothermal treatment. Additionally, the generation of micro/nanostructures resulted in mechanical strength enhancement for the 3D‐printed scaffolds.…”