Titanium-based composite scaffolds reinforced with hydroxyapatite-zirconia: Production, mechanical and in-vitro characterization

A numerical study on mechanical and permeability properties of novel design additive manufactured Titanium based metal matrix composite bone scaffold for bone tissue engineering

A novel design was developed for extrusion based additive manufacturing (robocasting) of bone scaffolds and a numerical study was carried out to find the optimal design to develop a bone scaffold for critical bone defect treatments. Initially, Representative Volume Analysis (RVE) analysis was carried out to predict the Young's modulus (E) of Titanium + Calcium Silicate and Titanium + Hydroxyapatite composites. The RVE analysis outputs were used to find out the E value of various bone scaffold designs and material compositions. The novel stepped design could be used to tailor the mechanical and biological properties of the scaffold by altering the contact support area between strands and changing the pore size, shape and orientation to control the permeability and nutrient transportation. The test revealed that some of the designed scaffolds are suitable for developing scaffolds for cortical bone defects as the E value lies between 10 and 30 GPa. The CFD analysis indicated that some designs do not possess the permeability required for a scaffold to aid nutrient transportation which is ideally between 1.5 × 10-9 and 5 × 10-8 m2. A sample model was printed and sintered in an argon atmosphere using a microwave furnace to check the feasibility of the process.

Porous titanium/hydroxyapatite interpenetrating phase composites with optimal mechanical and biological properties for personalized bone repair

This study introduces the first fabrication of porous titanium/hydroxyapatite interpenetrating phase composites through an innovative processing method. The approach combines additive manufacturing of a customized titanium skeleton with the infiltration of an injectable hydroxyapatite foam, followed by in situ foam hardening at physiological temperature. This biomimetic process circumvents ceramic sintering and metal casting, effectively avoiding the formation of secondary phases that can impair mechanical performance. Hydroxyapatite foams, prepared using two foaming agents (polysorbate 80 and gelatine), significantly reinforce the titanium skeleton while preserving the microstructural characteristics essential for osteoinductive properties. The strengthening mechanisms rely on the conformation of the foams to the titanium surface, thereby enabling stable mechanical interlocking and effective interfacial stress transfer. This, combined with the mechanical constriction of phases, enhances damage tolerance and mechanical reliability of the interpenetrating phase composites. In addition, the interpenetrating phase composites feature a network of concave pores with an optimal size for bone repair, support human osteoblast proliferation, and exhibit mechanical properties compatible with bone, offering a promising solution for the efficient and personalized reconstruction of large bone defects. The results demonstrate a significant advancement in composite fabrication, integrating the benefits of additive manufacturing for bone repair with the osteogenic capacity of calcium phosphate ceramics.

Tribological behavior and in vitro biocompatibility of powder metallurgical Ti-15Mo/HA composite for bone repair

Ti-15Mo/HA composite was prepared by powder metallurgy, and the influence of Hydroxyapatite (HA) on the microstructure, tribological behavior and in vitro biocompatibility was studied by comparison with TC4. The results show that the Ti-15Mo/HA composite consists of increased α-Ti, decreased β-Ti and a variety of ceramic phases (CaTiO3, Ca3(PO4)2, CaO, etc.) with the increase of HA content. The friction coefficient and wear rate of Ti-15Mo/HA composite is apparently lower than those of TC4 due to solid solution strengthening of Mo in Ti and dispersion strengthening of ceramic phases. Ti-15Mo/5HA displays more excellent wear resistance than the other composite. TC4 alloy is dominated by adhesive wear, however, Ti-15Mo alloy is a combination of adhesive wear and abrasive wear. Ti-15Mo/HA composite is mainly subjected to abrasive wear, together with adhesive wear. The viability and the number of mouse osteoblasts in Ti-15Mo/5HA extract are higher than that of Ti-15Mo. The morphology of the osteoblasts is clear and full, and the growth and proliferation are satisfactory with the increased cell pseudopodia with the culture time. The Ti-15Mo/HA composite displays good wear resistance and biocompatibility, and accordingly has a potential application in bone repair materials.

Metal Ion-Doped Hydroxyapatite-Based Materials for Bone Defect Restoration

Hydroxyapatite (HA)-based materials are widely used in the bone defect restoration field due to their stable physical properties, good biocompatibility, and bone induction potential. To further improve their performance with extra functions such as antibacterial activity, various kinds of metal ion-doped HA-based materials have been proposed and synthesized. This paper offered a comprehensive review of metal ion-doped HA-based materials for bone defect restoration based on the introduction of the physicochemical characteristics of HA followed by the synthesis methods, properties, and applications of different kinds of metal ion (Ag+, Zn2+, Mg2+, Sr2+, Sm3+, and Ce3+)-doped HA-based materials. In addition, the underlying challenges for bone defect restoration using these materials and potential solutions were discussed.

The practical process of manufacturing poly(methyl methacrylate)-based scaffolds having high porosity and high strength

Poly(methyl methacrylate) (PMMA)-based scaffolds have been produced using the granule casting method with grain sizes M80-100 and M100-140. The novelty of this study was the application of the cold-cutting method (CCm) to reduce the PMMA granule size. PMMA granule shape, granule size (mesh), and sintering temperature were the primary variables in manufacturing PMMA scaffolds. CCm was applied to reduce the granule size of commercial PMMA, which was originally solid cylindrical, by lowering the temperature to 3.5 °C, 0 °C, and-8.3 °C. PMMA granules that had been reduced were sieved with mesh sizes M80-100 and M100-140. Green bodies were made by the granule casting method using an aluminum mold measuring 8 × 8 × 8 mm³. The sintering process was carried out at temperatures varying from 115 °C to 140 °C, a heating rate of 5 °C/min, and a holding time of 2 h, the cooling process was carried out in a furnace. The characterization of the PMMA-based scaffolds' properties was carried out by observing the microstructure with SEM, analyzing the distribution of pore sizes with ImageJ software, and testing the porosity, the phase, with XRD, and the compressive strength. The best results from the overall analysis were the M80-100 PMMA scaffold treated at a sintering temperature of 130 °C with compressive strength, porosity, and pore size distribution values of 8.2 MPa, 62.0%, and 121-399 μm, respectively, and the M100-140 one treated at a sintering temperature of 135 °C with compressive strength, porosity, and pore size distribution values of 12.1 MPa, 61.2%, and 140-366 μm, respectively. There were interconnected pores in the PMMA scaffolds, as evidenced by the SEM images. There was no PMMA phase change between before and after the sintering process.