Creating hierarchical porosity hydroxyapatite scaffolds with osteoinduction by three-dimensional printing and microwave sintering

Abstract

Hierarchical porosity, which includes micropores and macropores in scaffolds, contributes to important multiple biological functions for tissue regeneration. This paper introduces a two-step method of combining three-dimensional printing (3DP) and microwave sintering to fabricate two-level hierarchical porous scaffolds. The results showed that 3D printing made the macroporous structure well-controlled and microwave sintering generated micropores on the macropore surface. The resulting hierarchical macro/microporous hydroxyapatite scaffold induced bone formation following intramuscular implantation. Moreover, when comparing the hierarchical macro/microporous hydroxyapatite scaffold to the non-osteoinductive hydroxyapatite scaffolds (either 3D printed or HO foamed) subjected to muffle sintering which do not have micropores, the critical role of micropores in material-driven bone formation was shown. The findings presented herein could be useful for the further optimization of bone grafting materials for bone regeneration.

Topography: A Biophysical Approach to Direct the Fate of Mesenchymal Stem Cells in Tissue Engineering Applications

“…However, prior reports have also found that pores larger than 200 µm were also able to promote vascularization and the formation of new bone [ 217 ]. Several studies have also found that smaller pores of around 50 to 100 µm were better for inducing endochondral ossification (i.e., osteochondral formation before osteogenesis) while, large pores (100–300 µm) promoted vascularization and were also beneficial for nutrient supply and waste removal [ 220 , 221 , 222 ]. Additionally, the porosity and connectivity among the pores are two important parameters.…”

Additive Manufacturing Methods for Producing Hydroxyapatite and Hydroxyapatite-Based Composite Scaffolds: A Review

“…Although AM methods exhibit considerable success in orthopedics, there are still certain challenges to be considered (e.g., resolution of printed constructs and mechanical properties) in the optimization of patient-specific scaffolds that may provide 3D micro-/nanoenvironment in hard tissue regeneration (Khalyfa et al, 2007;Derby, 2012). A significant number of scaffolds with bone regenerative properties have been investigated in preclinical studies (Xia et al, 2013;Ferlin et al, 2016;Pei et al, 2017), and even few clinical trials already have been performed by addressing translational methods. Moreover, AM methods facilitate the large number of reproducible anatomical geometries of the scaffolds with desired properties that match hard tissues or bone defects in patient-specific manner (Zhang et al, 2019).…”

“…The produced 3Dprinted scaffolds showed good porosity (49.8%) with pore size ranging within 300-400 µm and compressive strength of 15.25 MPa along with excellent biocompatibilities and promotion of osteoblast attachment, proliferation, and differentiation (Liu Z. et al, 2019). In addition, Pei et al introduced a two-step method consisting of extrusion-based 3D printing and microwave sintering to prepare dual-hierarchical porous scaffolds, where 3D printing creates a well-controlled macroporous structure and microwave-sintering creates a microporous network on the macroporous surface and demonstrated the role of micropores in scaffold-driven bone formation following intramuscular implantation (Pei et al, 2017).…”

Direct 3‐D printing of Ti‐6Al‐4V/HA composite porous scaffolds for customized mechanical properties and biological functions

“…Bone tissue scaffolds implantation is an important method of bone repair and reconstruction. As an indispensable role of bone tissue engineering, the scaffold provides spatial structures and growth templates, which play a vital effect in cell adhesion, proliferation, and differentiation (Chen et al, ; Pei, Ma, et al, ). Material is the fundamental factor that decides scaffold biofunctional performance.…”