A comparative study of 3D-printed scaffolds fabricated from different hydroxyapatite sources for bone tissue engineering applications

Abstract

As a naturally occurring mineral component of bone, hydroxyapatite (HA) is a preferred bone-repair material in clinical medicine. This adaptable biomaterial is developed from synthetic or biological sources. The goal of this study was to investigate the physicochemical and biological properties of scaffolds made from diverse hydroxyapatite sources. We prepared hydroxyapatite powders either from naturally occurring sources, using decellularized bone extracellular matrix (DBECM) and deproteinized bovine bone (DBB), or in the laboratory using the co-precipitation method. Although XRD analysis confirmed the pure phase of HA in all three powders, XRF data found some other trace elements in bone-derived biomaterials, such as magnesium and strontium. Further, FTIR spectra showed DBECM-associated macromolecule peaks. In the second phase of this study, the particles were mixed with sodium alginate to produce bioink for 3D printing via extrusion. SEM photographs of the printed scaffolds showed a grid-like porous structure with large, interconnected pores. Although all of the scaffolds retained their structural integrity after 28 days submerged in the culture medium, DBECM-based scaffolds degraded the most. The test of Young’s modulus and compressive strength of scaffolds revealed that all scaffolds are strong enough to be employed in non-weight-bearing applications. The biological characteristics of the scaffolds were then evaluated via cytotoxicity analysis, SEM examination of cell attachment, MTT assay, ALP activity assessment, immunofluorescence staining, and Alizarin red staining. The results indicated that all three scaffolds provided a surface that promoted adhesion and proliferation of rat bone marrow mesenchymal stem cells (rMSCs), as well as stimulated the production of mineralized extracellular matrices. Additionally, our findings showed that scaffolds made from DBECM powders offer the best environment for cell activity. This is most likely due to the presence of trace elements and protein macromolecules in DBECM powders that are not found in DBB and synthetic HA. In conclusion, our comparative study revealed that while all three scaffolds are suitable for bone tissue engineering, DBECM-based scaffolds outperform DBB and synthetic HA.