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In this study, a silver-modified layer was prepared on pure titanium through alkaline-heat treatment followed by hydrothermal sterilization in diluted silver nitrate (AgNO3) solutions at 121 °C for 20 min. The effects of the AgNO3concentration on the surface silver content, silver-containing particle distribution, and silver chemical state were investigated; the antibacterial properties of the surface-modified titanium samples against Staphylococcus aureusand their compatibility with MC3T3-E1 osteoblast-like cells were preliminarily evaluated. The results showed that the 3D network nanostructure constructed by alkaline-heat treatment on the pure titanium served as a matrix for the reduction of Ag+ions to silver nanoparticles (AgNPs) during the hydrothermal sterilization process without the addition of a reducing agent. These AgNPs evenly distributed without aggregation, and as the AgNO3concentration decreased from 10−2 mol/L to 10−6 mol/L, the number of AgNPs gradually decreased, but their size slightly changed. Silver-loaded surfaces exhibited good antibacterial and anti-adhesion properties. However, when the AgNO3concentration was greater than 10−4 mol/L, the number of AgNPs on the surface was excessive, resulting in significant cytotoxicity. When the AgNO3concentration was between 10−5and 10−6 mol/L, good antibacterial activity and good cell compatibility were achieved synchronously.

Mesoporous calcium phosphate based-bioceramics with ionic substitution have attracted attention for treatment of bone diseases and bone regeneration. Carbonate apatite (CO3Ap) is a promising candidate for bone replacement through bone remodelling, similar to that of autologous bone, owing to the chemical composition of the bone mineral. In this work, we present a dual approach to synthesize mesoporous carbonate apatite (CO3Ap) and strontium-substituted CO3Ap (Sr-CO3Ap) artificial bone nanocrystals, aiming to assess the impact of strontium on CO3Ap characteristics and biological performance. Mesoporous CO3Ap was created by transforming hard templates composed of CaCO3, while Sr-substituted CaCO3(Sr-CaCO3) microspheres were formed using an organic complexing agent to induce pore formation. The resulting CO3Ap and Sr-CO3Ap granules exhibited an irregular shape, with rod-like nanocrystals composing their particles. Adsorption/desorption isotherms confirmed the mesoporous nature of the structures, featuring pore sizes ranging from 10 to 50 nm. Specifically, mesoporous CO3Ap displayed slit-like pores, while Sr-CO3Ap showed cylinder-like ones. High-resolution transmission electron microscopy images of Sr-CO3Ap powder revealed mesopores within the particles, with Sr-CO3Ap exhibiting larger pore volume and specific surface area compared to CO3Ap. When osteoblast-like MC3T3-E1 cells were cultured on both CO3Ap and Sr-CO3Ap samples, they demonstrated good cell attachment, proliferation rates, and increased ALP activity, particularly evident at higher strontium concentrations. These findings suggest promising potential for further exploration of mesoporous apatite nanocrystals in bone replacement and drug delivery applications.

The effect of 1 wt% magnesium oxide (MgO) as sintering additive on the sintering behaviour, microstructure, mechanical properties and cell activities of 0.4 and 1.6 wt% silicon-substituted hydroxyapatite (MgO-0.4Si-HA and MgO-1.6Si-HA) was investigated. The powders were synthesized by the wet-chemical neutralization method and the compacts were pressureless sintered in air between 1150 and 1250 °C for 2 h. The results showed that MgO-0.4Si-HA promoted the formation of the secondary phase of β-TCP when sintered at 1250 °C, whilst the stability of the hydroxyapatite phase was not disrupted for the MgO-1.6Si-HA. The presence of MgO was found to be beneficial in suppressing grain growth of Si-HA when sintered at 1250 °C; however, it did not promote densification at lower temperatures (1150 and 1200 °C). It was observed that despite the lower densification, Vickers hardness and compressive strength of the MgO-Si-HA were higher than those of the undoped Si-HA samples. The beneficial effect of MgO in enhancing the biocompatibility of Si-HA has been revealed. It was found that the MgO-doped samples dramatically enhanced the osteogenic differentiation of MC3T3-E1 cells as shown from the higher cell proliferation, alkaline phosphatase activity and bone-like nodule formation when compared to pristine HA.

Ultrafine-grained pure (UFG) titanium processed by equal channel angular pressing possesses mechanical properties comparable to those of Ti-6Al-4V and features more favorable friction resistance, biocompatibility, and corrosion resistance than does commercially pure (CP) titanium. Nevertheless, UFG titanium is still a bio-inert material with a lack of bone-inducing ability. Here, TiO2-hydroxyapatite (TiO2-HA) coatings were fabricated on CP titanium and UFG titanium through combining micro-arc oxidation and hydrothermal treatment together to improve their cytocompatibility. The results indicate that, compared with conventional coatings that use CP titanium as the substrate, such coatings formed on the UFG titanium possess additional hydrophilicity and in vitro cytocompatibility. The fantastic hierarchical structure of the UFG TiO2-HA coating (UG-MH coating), including microscale and nanoscale pores and short column-shaped and sheet-shaped HA grains with varying geometric shapes, excellent hydrophilicity, and high polar force, enhances the mutual effects between the osteoblasts and titanium implant since it provides an adequate microenvironment for the ingrowth of osteoblasts, inducing osteoblast adhesion, proliferation, and differentiation. The UG-MH coating has a synergistic effect due to its fantastic hydrophilic hierarchical structure and high polar force on the up-regulated expression of cytoskeletal actin proteins as well as osteocalcin, protein kinase C (PKC), nuclear factor of activated T-cells (NFAT), and Wnt5, enabling osteoblasts to differentiate via the Wnt calcium-dependent signaling pathway. This study highlights the idea that the modified UFG titanium will be more suitable than CP titanium in dental and orthopedic applications.

Chemically formed phosphate conversion coatings (PCC) usually have good adhesion strength due to in situ growth and have great potential for biomedical applications. However, the fabrication of PCC on titanium (Ti) metals has seldom been studied because inherent chemical inertia and oxide layer block the dissolving process. Previously, the authors successfully fabricate intact PCC on pure Ti by a novel hydrothermal phosphorization method, and the coating shows good adhesion. However, metallographically polished specimens are used only in order to eliminate the influences of surface topography. In this study, the feasibility of such method to be performed on sandpaper polished and acid‐etched pure Ti are studied. Results show that rough surface benefit the nucleation of PCC and refine the crystal size, whereas, a smooth surface allow sufficient growth of crystal grain resulting in a thicker coating with stronger adhesive strength. In spite of rough surface, PCC formation on acid‐etched Ti is depressed due to the existence of titanium hydride. All the coatings obviously improve corrosion resistance of Ti substrate. The cytotoxicity test suggests that the PCCs present no adverse effects on L‐929 cells and has a cytotoxicity ranking of 0–I grade. The study shows that the hydrothermal zinc phosphorization has a potential to be extensively used for Ti‐based implants with different surface finishes. In situ phosphate conversion coatingis prepared on pure titanium using hydrothermal method. Titanium dissolves into solution and forms compound of tetragonal structure, defined as Ti‐Zn‐PO4. Surface finishing affects the growth and morphology of the coating. Smoother surface facilities granule growing and increases thickness of the coating, which ensure a compact structure, stronger adhesion, and better corrosion resistance.