Potential Load-Bearing Bone Substitution Material: Carbon-Fiber-Reinforced Magnesium-Doped Hydroxyapatite Composites with Excellent Mechanical Performance and Tailored Biological Properties

Construction of multileveled and oriented micro/nano channels in Mg doped hydroxyapitite bioceramics and their effect on mimicking mechanical property of cortical bone and biological performance of cancellous bone

Drawing on the structure and components of natural bone, this study developed Mg-doped hydroxyapatite (Mg-HA) bioceramics, characterized by multileveled and oriented micro/nano channels. These channels play a critical role in ensuring both mechanical and biological properties, making bioceramics suitable for various bone defects, particularly those bearing loads. Bioceramics feature uniformly distributed nanogrooves along the microchannels. The compressive strength or fracture toughness of the Mg-HA bioceramics with micro/nano channels formed by single carbon nanotube/carbon fiber (CNT/CF) (Mg-HA(05-CNT/CF)) are comparable to those of cortical bone, attributed to a combination of strengthened compact walls and microchannels, along with a toughening mechanism involving crack pinning and deflection at nanogroove intersections. The introduction of uniform nanogrooves also enhanced the porosity by 35.4 %, while maintaining high permeability owing to the capillary action in the oriented channels. This leads to superior degradation properties, protein adsorption, and in vivo osteogenesis compared with bioceramics with only microchannels. Mg-HA(05-CNT/CF) exhibited not only high strength and toughness comparable to cortical bone, but also permeability similar to cancellous bone, enhanced cell activity, and excellent osteogenic properties. This study presents a novel approach to address the global challenge of applying HA-based bioceramics to load-bearing bone defects, potentially revolutionizing their application in tissue engineering.

Biphasic Calcium Phosphate and Activated Carbon Microparticles in a Plasma Clot for Bone Reconstruction and In Situ Drug Delivery: A Feasibility Study

The development of bone-filling biomaterials capable of delivering in situ bone growth promoters or therapeutic agents is a key area of research. We previously developed a biomaterial constituting biphasic calcium phosphate (BCP) microparticles embedded in an autologous blood or plasma clot, which induced bone-like tissue formation in ectopic sites and mature bone formation in orthotopic sites, in small and large animals. More recently, we showed that activated carbon (AC) fiber cloth is a biocompatible material that can be used, due to its multiscale porosity, as therapeutic drug delivery system. The present work aimed first to assess the feasibility of preparing calibrated AC microparticles, and second to investigate the properties of a BCP/AC microparticle combination embedded in a plasma clot. We show here, for the first time, after subcutaneous (SC) implantation in mice, that the addition of AC microparticles to a BCP/plasma clot does not impair bone-like tissue formation and has a beneficial effect on the vascularization of the newly formed tissue. Our results also confirm, in this SC model, the ability of AC in particle form to adsorb and deliver large molecules at an implantation site. Altogether, these results demonstrate the feasibility of using this BCP/AC/plasma clot composite for bone reconstruction and drug delivery.

Synthesis Technology of Magnesium-Doped Nanometer Hydroxyapatite: A Review

Ion substitution techniques for nanoparticles have become an important neighborhood of biomedical engineering and have led to the development of innovative bioactive materials for health systems. Magnesium-doped nanohydroxyapatite (Mg-nHA) has good bone conductivity, biological activity, flexural strength, and fracture toughness due to particle doping technology, making it an ideal candidate material for biomedical applications. In this Review, we have systematically presented the synthesis methods of Mg-nHA and their application in the field of biomedical science and highlighted the pros and cons of each method. Finally, some future prospects for this important neighborhood are proposed. The purpose of this Review is to provide readers with an understanding of this new field of research on bioactive materials with innovative functions and systematically introduce the latest technologies for obtaining uniform, continuous, and morphologically diverse Mg-nHA.

Group Replacement-Rearrangement-Triggered Linear-Assembly Nonaqueous Precipitation Synthesis of Hydroxyapatite Fibers

A novel method for hydroxyapatite fiber preparation with highly large-scale production prospects is of paramount importance but remains particularly difficult. Here, group replacement-rearrangement-triggered linear-assembly nonaqueous precipitation synthesis has been proposed for hydroxyapatite fibers under mild conditions. Pure hydroxyapatite fibers can be fabricated taking disodium hydrogen phosphate, calcium acetate, and glycerol as the phosphorus source, calcium source, and solvent, respectively. Single hexagonal crystal structures of hydroxyapatite fibers growing along the c-axis and preferential growth of the (002) crystal plane similar to the layered stacking structure of an adult bone have been confirmed by XRD refinement tests and calculation, TEM electron diffraction calibration, and FE-SEM. Highly active carbonate apatite is further demonstrated by EDS, FT-IR, Raman spectroscopy, and XPS. Unsaturated P-O and O-Ca bonds at both ends of the hexagonal-sheet assembly unit in a high-polarity nonaqueous glycerol environment without strongly coordinated OH- confirm the solution spontaneous linear assembly to form the single hydroxyapatite fibers.