Hierarchically porous 3D printed hydroxyapatite scaffolds for biomedical applications

Hydroxyapatite (HAp), a natural mineral form of calcium apatite, with formula Ca10(PO4)6(OH)2 , is a main component of bones. In recent years, interest in bone tissue engineering has grown, focusing on biomaterials, such as HAp, for treating bone diseases or creating scaffolds for bone replacements, due to its mechanical properties, biocompatibility, biodegradability and porosity. This study focuses on the production and characterisation of 3D-printed porous scaffolds made of commercial hydroxyapatite, designed to mimic the natural structure of bone and support cell adhesion and growth. To improve the scaffolds’ porosity two pore forming agents were used: polymethyl methacrylate microbeads and hydrogen peroxide, along with (hydroxypropyl) methyl cellulose to adapt the rheology. These additives, combined with the scaffold structure’s intrinsic macroporosity, create hierarchical porosity, which should enhance the attachment and proliferation of cells. Bioactivity and biocompatibility of the scaffolds were assessed by soaking them in simulated body fluid, and performing MTT assay with MG-63 cells. SEM was used to evaluate the formation of new HAp crystals on the surface of the scaffolds and the morphology of the scaffolds, XRD for phase composition, and FTIR Spectroscopy for chemical structure. Mechanical strength of the scaffolds was assessed via compression tests, and the photocatalytic activity by monitoring methylene blue photodegradation under UV and visible light.