Incorporation of HA into porous titanium to form Ti-HA biocomposite foams

Hydroxyapatite-Coated Titanium by Micro-Arc Oxidation and Steam-Hydrothermal Treatment Promotes Osseointegration

Titanium (Ti)-based alloys are widely used in tissue regeneration with advantages of improved biocompatibility, high mechanical strength, corrosion resistance, and cell attachment. To obtain bioactive bone–implant interfaces with enhanced osteogenic capacity, various methods have been developed to modify the surface physicochemical properties of bio-inert Ti and Ti alloys. Nano-structured hydroxyapatite (HA) formed by micro-arc oxidation (MAO) is a synthetic material, which could facilitate osteoconductivity, osteoinductivity, and angiogenesis on the Ti surface. In this paper, we applied MAO and steam–hydrothermal treatment (SHT) to produce HA-coated Ti, hereafter called Ti–M–H. The surface morphology of Ti–M–H1 was observed by scanning electron microscopy (SEM), and the element composition and the roughness of Ti–M–H1 were analyzed by energy-dispersive X-ray analysis, an X-ray diffractometer (XRD), and Bruker stylus profiler, demonstrating the deposition of nano-HA particles on Ti surfaces that were composed of Ca, P, Ti, and O. Then, the role of Ti–M–H in osteogenesis and angiogenesis in vitro was evaluated. The data illustrated that Ti–M–H1 showed a good compatibility with osteoblasts (OBs), which promoted adhesion, spreading, and proliferation. Additionally, the secretion of ALP, Col-1, and extracellular matrix mineralization was increased by OBs treated with Ti–M–H1. Ti–M–H1 could stimulate endothelial cells to secrete vascular endothelial growth factor and promote the formation of capillary-like networks. Next, it was revealed that Ti–M–H1 also suppressed inflammation by activating macrophages, while releasing multiple active factors to mediate osteogenesis and angiogenesis. Finally, in vivo results uncovered that Ti–M–H1 facilitated a higher bone-to-implant interface and was more attractive for the dendrites, which promoted osseointegration. In summary, MAO and SHT-treated Ti–M–H1 not only promotes in vitro osteogenesis and angiogenesis but also induces M2 macrophages to regulate the immune environment, which enhances the crosstalk between osteogenesis and angiogenesis and ultimately accelerates the process of osseointegration in vivo.

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

In this study, titanium (Ti)-based composite scaffolds reinforced with hydroxyapatite-zirconia (HA-ZrO₂) were successfully produced with powder metallurgy and atmosphere-controlled sintering processes. The scaffolds structures were theoretically selected as 40% and 60% porosity, and fabricated with approximately 1.47 and 4.02 std dev values, respectively. The porosity of the scaffolds was verified by Archimedes' measurements. The scaffolds were characterized by DTA, SEM/EDS, XRD analyses. The mechanical behaviors of the scaffolds were evaluated by compression and hardness tests. Besides, the electrochemical corrosion behaviors of the structures were compared with potentiodynamic scanning (PDS) measurements in simulated body fluids (SBF) at 37 ± 1 °C. It has been observed that all scaffolds have a bimodal porous structure as they contain varying proportions of micropores as well as macropores in desired dimensions. Biocompatible phases such as Ti_xP_y, Ca₃(PO₄)₂ and CaTiO₃, respectively, were found in the microstructure after sintering. In compression tests, 40% porous Ti had the highest strength with 37.98 MPa, interestingly, the lowest strength was seen in Ti/HA-ZrO₂ scaffold with 60% porosity with 3.80 MPa. Young's modulus values of all scaffolds vary between 1.67 - 7.20 GPa, due to the bimodal pore structure and composition effect. However, in-vitro corrosion resistance of scaffolds decreased with HA reinforcement, while increased with ZrO₂ additive to HA.

Structural and Material Determinants Influencing the Behavior of Porous Ti and Its Alloys Made by Additive Manufacturing Techniques for Biomedical Applications

One of the biggest challenges in tissue engineering is the manufacturing of porous structures that are customized in size and shape and that mimic natural bone structure. Additive manufacturing is known as a sufficient method to produce 3D porous structures used as bone substitutes in large segmental bone defects. The literature indicates that the mechanical and biological properties of scaffolds highly depend on geometrical features of structure (pore size, pore shape, porosity), surface morphology, and chemistry. The objective of this review is to present the latest advances and trends in the development of titanium scaffolds concerning the relationships between applied materials, manufacturing methods, and interior architecture determined by porosity, pore shape, and size, and the mechanical, biological, chemical, and physical properties. Such a review is assumed to show the real achievements and, on the other side, shortages in so far research.