Effect of Partial Substitution of Zr for Ti Solvent on Young's Modulus, Strength, and Biocompatibility in Beta Ti Alloy.

In orthopedics and dentistry, there is an urgent need to obtain low-stiffness implants that suppress the stress shielding caused by the use of metallic implants. In this study, we aimed to fabricate alloys that can reduce the stiffness by increasing the strength while maintaining a low Young's modulus based on the metastable ß-Ti alloy. We designed alloys in which Ti was partially replaced by Zr based on the ISO-approved metastable ß-Ti alloy Ti-15Mo-5Zr-3Al. All alloys prepared by arc melting and subsequent solution treatment showed a single ß-phase solid solution, with no formation of the ω-phase. The alloys exhibited a low Young's modulus equivalent to that of Ti-15Mo-5Zr-3Al and a high strength superior to that of Ti-15Mo-5Zr-3Al and Ti-6Al-4V. This strengthening was presumed to be due to solid-solution strengthening. The biocompatibility of the alloys was as good as or better than that of Ti-6Al-4V. These alloys have potential as metallic materials suitable for biomedical applications.

An increase in Wharton's jelly membrane osteocompatibility by a genipin-cross-link.

Wharton's Jelly (WJ) has attracted significant interest in the field of tissue healing thanks to its biological properties, including antibacterial activity and immunomodulation. However, due to the fast degradation and poor mechanical behavior in biological environment, its application in bone regeneration is compromised. Here, we proposed to use genipin as an efficient cross-linking agent to significantly improve the elasticity and the enzymatical stability of the WJ matrix. The degree of cross-linking, linear elastic moduli, and collagenase resistance varied over a wide range depending on genipin concentration. Furthermore, our results highlighted that an increase in genipin concentration led to a decreased surface wettability, therefore impairing cell attachment and proliferation. The genipin cross-linking prevented rapid in vitro and in vivo degradation, but led to an adverse host reaction and calcification. When implanted in the parietal bone defect, a limited parietal bone regeneration to the dura was observed. We conclude that genipin-cross-linked WJ is a versatile medical device however, a careful selection is required with regards to the genipin concentration.

Electroplating of HAp-brushite coating on metallic bioimplants with advanced hemocompatibility and osteocompatibility properties.

In cases of severe bone tissue injuries, the use of metallic bioimplants is quite widespread due to their high strength, high fracture toughness, hardness, and corrosion resistance. However, they lack adequate biocompatibility and show poor metal-tissue integration during the post-operative phase. To mitigate this drawback, it is beneficial to add a biocompatible polymer layer to ensure a quick growth of cell or tissue over the surface of metallic bioimplant material. Furthermore, this additional layer should possess good adherence with the underlying material and also accompany a rapid bonding between the tissue and the implant material, in order to reduce the recovery time for the patient. Therefore, in this work, we report a novel green electroplating route for growing porous hydroxyapatite-brushite coatings on a stainless steel surface. The malic acid used for the production of hydroxyapatite-brushite coatings has been obtained from an extract of locally available apple fruit (Malus domestica). We demonstrate the effect of electroplating parameters on the structural morphology of the electroplated composite layer via XRD, SEM with EDS, and FTIR characterization techniques and report an optimized set of electroplating parameters that will yield the best composite coating in terms of thickness, adherence to substrate and speed. The hemocompatibility and osteocompatibility studies on the electroplated composites coating show this technology's effectiveness and potential applicability in biomedical applications. Compared to other routes reported in the literature, this electroplating route is quicker and yields better composite coatings with faster bone tissue growth potential.

Biological Safety Evaluation and Surface Modification of Biocompatible Ti-15Zr-4Nb Alloy.

We performed biological safety evaluation tests of three Ti-Zr alloys under accelerated extraction condition. We also conducted histopathological analysis of long-term implantation of pure V, Al, Ni, Zr, Nb, and Ta metals as well as Ni-Ti and high-V-containing Ti-15V-3Al-3Sn alloys in rats. The effect of the dental implant (screw) shape on morphometrical parameters was investigated using rabbits. Moreover, we examined the maximum pullout properties of grit-blasted Ti-Zr alloys after their implantation in rabbits. The biological safety evaluation tests of three Ti-Zr alloys (Ti-15Zr-4Nb, Ti-15Zr-4Nb-1Ta, and Ti-15Zr-4Nb-4Ta) showed no adverse (negative) effects of either normal or accelerated extraction. No bone was formed around the pure V and Ni implants. The Al, Zr, Nb, and Ni-Ti implants were surrounded by new bone. The new bone formed around Ti-Ni and high-V-containing Ti alloys tended to be thinner than that formed around Ti-Zr and Ti-6Al-4V alloys. The rate of bone formation on the threaded portion in the Ti-15Zr-4Nb-4Ta dental implant was the same as that on a smooth surface. The maximum pullout loads of the grit- and shot-blasted Ti-Zr alloys increased linearly with implantation period in rabbits. The pullout load of grit-blasted Ti-Zr alloy rods was higher than that of shot-blasted ones. The surface roughness (Ra) and area ratio of residual Al2O3 particles of the Ti-15Zr-4Nb alloy surface grit-blasted with Al2O3 particles were the same as those of the grit-blasted Alloclassic stem surface. It was clarified that the grit-blasted Ti-15Zr-4Nb alloy could be used for artificial hip joint stems.

Ultraviolet irradiation assisted liquid phase deposited titanium dioxide (TiO2)-incorporated into phytic acid coating on magnesium for slowing-down biodegradation and improving osteo-compatibility.

It remains challenging to build up a multifunctional coating onto biodegradable magnesium (Mg) for biomedical use. In this study, a small amount of titanium dioxide (TiO2) has been incorporated in situ into phytic acid (PA) coating when it was chemically deposited on Mg substrate targeted to biodegradable implant applications. Ultraviolet (UV) irradiation was utilized in the liquid phase deposition of TiO2 to improve the quality of coating (PA&TiO2-UV). This PA&TiO2-UV coating was compact, thicker and more hydrophilic compared with sole PA or TiO2 coating. The PA&TiO2-UV coated Mg presented a seven times lower electrochemical corrosion current density as well as significantly slower in vitro degradation rate up to 500 h in phosphate buffer saline as compared to the direct PA coated Mg. In addition, the UV irradiation showed remarkably to promote the MC3T3-E1 pre-osteoblast cells adhesion and proliferation especially after 7 days of culture. Further, the PA&TiO2-UV coating adhered more firmly on Mg substrate after 90° bending than the other coatings, indicating a better mechanical compliance on Mg substrate. These results make this PA&TiO2-UV complex coating bodes well for biodegradation slowing-down, osteo-compatible as well as mechanical compliant modification of Mg for orthopedic implants applications.

In Vitro Osteocompatibility and Enhanced Biocorrosion Resistance of Diammonium Hydrogen Phosphate-Pretreated/Poly(ether imide) Coatings on Magnesium for Orthopedic Application.

Magnesium, as a biodegradable metal, is a promising candidate for biomedical applications. To modify the degradation behavior of magnesium and improve its osteocompatibility, chemical conversion and spin coating methods were combined to develop a diammonium hydrogen phosphate-pretreated/poly(ether imide) (DAHP/PEI) co-coating system. The diammonium hydrogen phosphate pretreatment was employed to enhance the attachment between PEI coatings and the magnesium substrate; meanwhile, it could serve as another bioactive and anticorrosion layer when PEI coatings break down. Surface characterization, electrochemical tests, and short-term immersion tests in DMEM were performed to evaluate DAHP/PEI coatings. Electrochemical measurements showed that DAHP/PEI coatings significantly improved the corrosion resistance of pure magnesium. No obvious changes of the chemical compositions of DAHP/PEI coatings occurred after 72 h of immersion in DMEM. An in vitro cytocompatibility study confirmed that viability and LDH activity of human osteoblast-like cells on DAHP/PEI coatings showed higher values than those on the DAHP-pretreated layer and pure magnesium. The DAHP-pretreated layer could still enhance the ALP activity of MG-63 cells after the degradation of PEI in DAHP/PEI coatings. Besides that, the in vitro cellular response to the treated magnesium was investigated to gain knowledge on the differentiation and proliferation of human adipose-derived stem cells (hADSCs). Cell distribution and morphology were observed by fluorescence and SEM images, which demonstrated that DAHP/PEI coatings facilitated cell differentiation and proliferation. The high level of C-terminals of collagen type I production of hADSCs on DAHP/PEI coatings indicated the potential of the coating for promoting osteogenic differentiation. Positive results from long-term cytocompatibility and proliferation tests indicate that DAHP/PEI coatings can offer an excellent surface for hADSCs.

Promoting osteogenic differentiation of BMSCs via mineralization of polylactide/gelatin composite fibers in cell culture medium.

Mineralization capability is an important issue in developing bone repairing biomaterials, while it is not quite clear how this feature would act in the presence of cells and influence cell osteogenic differentiation without adding extra osteoinductive factors such as ß­sodium glycerophosphate and dexamethasone. Poly(l­lactide) (PLLA) and gelatin composite fibers (PG, 1:1 in weight) were electrospun, treated with CaCl2 solution (PG-Ca), and used for mineralization studies by using cell culture media (αMEM, and αMEM + serum). Bone mesenchymal stromal cells (BMSCs) were then seeded and cultured on both PG and PG-Ca fibrous mats for 28 days by only using αMEM + serum. Interestingly, mineral depositions on both PG and PG-Ca fibers were detected in the environment of αMEM or αMEM + serum, in which, PG-Ca fibers demonstrated stronger ability in inducing hydroxyapatite formation than PG fibers, especially in the presence of fetal bovine serum. When BMSCs were cultured on the two kinds of fibrous mats, apatite depositions were still clearly detected, while the depositing amounts decreased in comparison with corresponding cell-free cases. It was ascribed to the consumption of ions by the continuously proliferating BMSCs, whose osteogenic differentiation was significantly promoted even without extra osteoinductive factors, especially on PG-Ca fibrous mats, in comparison with the control group. Therefore, it was confirmed the capability of scaffolding materials in enriching ions like calcium and phosphate around cells was an efficient way to promote bone regeneration.

Synthesis and osteo-compatibility of novel reduced graphene oxide-aminosilica hybrid nanosheets.

Combination of silica component with other materials is one of the current strategies to design bone regenerative materials. In this study, novel reduced graphene oxide (RGO)-aminosilica hybrid nanosheets with enhanced osteo-compatibility were synthesized from a mixture of 3-aminopropyltriethoxysilane (APTES), graphene oxides (GO) and water. The presence of APTES in the mixture not only caused the conversion of GO to RGO, but also led to the hydrolysis and condensation of itself. It was for the first time reported the reducing role of APTES in the conversion of GO to RGO. It was found that the silicon (IV) ions were released from the hybrid nanosheets in a sustained way. The in vitro osteo-compatibility was evaluated by incubating the hybrid nanosheets with osteoblast MC3T3-E1 cells. A water soluble tetrazolium salt assay quantitatively indicated that the hybrid nanosheets had no significant toxicity and exhibited good biocompatibility. An alkaline phosphatase assay quantitatively indicated that the hybrid nanosheets enhanced the osteoblast differentiation compared to the GO nanosheets. An immunochemical assay further qualitatively indicated that the hybrid nanosheets stimulated the production of osteopontin as typical marker for osteoblast differentiation. Thus, the resultant hybrids nanosheets had a potential application in the bone regeneration.