In vitro bioactivity and phase stability of plasma-sprayed nanostructured 3Y-TZP coatings

The mineralization, drug release and in vivo bone defect repair properties of calcium phosphates/PLA modified tantalum scaffolds

Calcium phosphate based biomaterials have been widely studied in biomedical areas. Herein, amorphous calcium phosphate (ACP) nanospheres and hydroxyapatite (HA) nanorods were separately prepared and used for coating tantalum (Ta) scaffolds with a polymer of polylactide (PLA). We have found that different crystal phases of calcium phosphate coated on Ta scaffolds displayed different effects on the surface morphologies, mineralization and bovine serum albumin (BSA) release. The ACP-PLA and HA-PLA coated on Ta scaffold were more favorable for in vitro mineralization than bare and PLA coated Ta scaffolds, and resulted in a highly hydrophilic surfaces. Meanwhile, the osteoblast-like cells (MG63) showed favorable properties of adhesion and spreading on both ACP-PLA and HA-PLA coated Ta scaffolds. The ACP-PLA and HA-PLA coated Ta scaffolds showed a high biocompatibility and potential applications for in vivo bone defect repair.

Calcium phosphate modified tantalum scaffolds displayed high performance on mineralization, sustained drug release and in vivo bone defect repair.

Synthesis, characterization, and cytocompatibility of yttria stabilized zirconia nanopowders for creating a window to the brain

Transparent cranial window to the brain is highly desirable for brain therapies because such cranial implant would allow for continuous monitoring of brain disorders and long-term delivery of photodynamic therapy into the brain without repeated surgeries for opening skull. Nanostructured yttria-stabilized zirconia (YSZ) is a potential candidate for the window to the brain application because of its promising mechanical and optical properties. In this study, a new process using aerosol spray pyrolysis was established for synthesizing 6-7 nm YSZ nanopowders with precisely controlled compositions. YSZ nanopowders with 3 M ratios of yttria to zirconia, specifically 3, 6, and 8% yttria in zirconia (referred to as 3YSZ, 6YSZ, and 8YSZ, respectively) were synthesized and characterized. The size, structure, and composition of the produced YSZ nanoparticles are highly controllable and scalable. The in vitro cytocompatibility of the YSZ nanoparticles with bone marrow mesenchymal stem cells (BMSCs) was investigated using a direct exposure culture method for cranial implant applications. Nondoped ZrO₂ and commercially available 8YSZ (named as C_8YSZ) served as controls for the in vitro cell studies. BMSCs exhibited normal morphology when cultured with the YSZs of 3 M ratios in the concentrations of 10 mM, 30 mM, and 60 mM, as well as ZrO₂ and C_8YSZ controls. The BMSCs cultured with 3YSZ and 6YSZ showed no statistical differences in cell adhesion density when compared with the ZrO₂ and C_8YSZ controls at respective concentrations of 10-60 mM. The possible release of YSZ nanoparticles from cranial window implants should be carefully considered and further studied.

Enhancing orthopedic implant bioactivity: refining the nanotopography

Advances in nanotechnology open up new possibilities to produce biomimetic surfaces that resemble the cell in vivo growth environment at a nanoscale level. Nanotopographical changes of biomaterials surfaces can positively impact the bioactivity and ossointegration properties of orthopedic and dental implants. This review introduces nanofabrication techniques currently used or those with high potential for use as surface modification of biomedical implants. The interactions of nanotopography with water, proteins and cells are also discussed, as they largely determine the final success of the implants. Due to the well-documented effects of surface chemistry and microtopography on the bioactivity of the implant, we here elaborate on the ability of the nanofabrication techniques to combine the dual (multi) modification of surface chemistry and/or microtopography.

Refining nanotopographical features on bone implant surfaces by altering surface chemical compositions

Nb₂O₅/TiO₂ composite coatings with controllable nanostructures were achieved by adjusting the amount of Nb₂O₅ in one simple and single plasma spraying process and Nb₂O₅ doping showed its potential use in enhancing the biological properties of biomedical TiO₂ coatings.

Delicate refinement of surface nanotopography by adjusting TiO2 coating chemical composition for enhanced interfacial biocompatibility

Surface topography and chemistry have significant influences on the biological performance of biomedical implants. Our aim is to produce an implant surface with favorable biological properties by dual modification of surface chemistry and topography in one single simple process. In this study, because of its chemical stability, excellent corrosion resistance, and biocompatibility, titanium oxide (TiO2) was chosen to coat the biomedical Ti alloy implants. Biocompatible elements (niobium (Nb) and silicon (Si)) were introduced into TiO2 matrix to change the surface chemical composition and tailor the thermophysical properties, which in turn leads to the generation of topographical features under specific thermal history of plasma spraying. Results demonstrated that introduction of Nb2O5 resulted in the formation of Ti0.95Nb0.95O4 solid solution and led to the generation of nanoplate network structures on the composite coating surface. By contrast, the addition of SiO2 resulted in a hairy nanostructure and coexistence of rutile and quartz phases in the coating. Additionally, the introduction of Nb2O5 enhanced the corrosion resistance of TiO2 coating, whereas SiO2 did not exert much effect on the corrosion behaviors. Compared to the TiO2 coating, TiO2 coating doped with Nb2O5 enhanced primary human osteoblast adhesion and promoted cell proliferation, whereas TiO2 coatings with SiO2 were inferior in their bioactivity, compared to TiO2 coatings. Our results suggest that the incorporation of Nb2O5 can enhance the biological performance of TiO2 coatings by changing the surface chemical composition and nanotopgraphy, suggesting its potential use in modification of biomedical TiO2 coatings in orthopedic applications.

Nanostructured glass-ceramic coatings for orthopaedic applications

Glass-ceramics have attracted much attention in the biomedical field, as they provide great possibilities to manipulate their properties by post-treatments, including strength, degradation rate and coefficient of thermal expansion. In this work, hardystonite (HT; Ca2ZnSi2O7) and sphene (SP; CaTiSiO5) glass-ceramic coatings with nanostructures were prepared by a plasma spray technique using conventional powders. The bonding strength and Vickers hardness for HT and SP coatings are higher than the reported values for plasma-sprayed hydroxyapatite coatings. Both types of coatings release bioactive calcium (Ca) and silicon (Si) ions into the surrounding environment. Mineralization test in cell-free culture medium showed that many mushroom-like Ca and phosphorus compounds formed on the HT coatings after 5 h, suggesting its high acellular mineralization ability. Primary human osteoblasts attach, spread and proliferate well on both types of coatings. Higher proliferation rate was observed on the HT coatings compared with the SP coatings and uncoated Ti-6Al-4V alloy, probably due to the zinc ions released from the HT coatings. Higher expression levels of Runx2, osteopontin and type I collagen were observed on both types of coatings compared with Ti-6Al-4V alloy, possibly due to the Ca and Si released from the coatings. Results of this study point to the potential use of HT and SP coatings for orthopaedic applications.

Silver nanoparticles-modified films versus biomedical device-associated infections

A serious issue related to biomedical devices (BDs) is that of bacterial infections. BDs colonized by bacteria may cause infection or mortality. To prevent such infections, an effective strategy is to develop novel BDs with antibacterial abilities via various surface modification processes. Thus, plenty of silver nanoparticles (Ag NPs)-modified films were brought forward to because of their potential applications in improving the antibacterial properties of BDs. This article reviews the difficulties in diagnosing and treating biomedical device-associated infections as well as the state of arts in fabricating the Ag NPs-modified films for antibacterial applications. In addition, the nanoeffect of silver particles and the cytotoxicity of Ag NPs are also discussed. It is clear that safe and durable Ag NPs-modified films are more desirable for the BDs prone to bacteria. To further extend the investigations on controlling the toxicity path of Ag NPs to both bacteria and mammalian cells, developing novel green fabrication processes with more 'cleaner' (without accompaniment of ligands or reduction agents) Ag NPs should be the first mission for the material scientists to complete.

Osteoblastic cell response on fluoridated hydroxyapatite coatings: the effect of magnesium incorporation

Magnesium (Mg) ions were incorporated into fluoridated hydroxyapatite (HA) coating by the sol-gel dip-coating method. Mg in the coating was measured by x-ray photoelectron spectroscopy (XPS). The changes of calcium and magnesium concentrations were recorded to monitor the dissolution behavior of the coatings. In vitro cell responses were evaluated using MG63 cells in terms of cell morphology, proliferation and differentiation. The substitution of Mg and F ions into the HA crystal structure was confirmed by XPS. Only a limited amount of Mg can be incorporated into HA lattice. The dissolution test revealed that Mg incorporation increased the solubility of the coating in the tris-buffered saline solution. The highest solubility was achieved at x = 1.5 (Ca((10-x))Mg(x)(PO(4))(6) F(OH). In the cell culture test, well-spread cells were observed on all the coatings. Also, a significantly positive effect of Mg ions on cell proliferation and late differentiation was found at x = 1.5. Mg incorporation stimulates osteoblastic cell responses on fluoridated hydroxyapatite coatings.

Microstructure, bioactivity and osteoblast behavior of monoclinic zirconia coating with nanostructured surface

A monoclinic zirconia coating with a nanostructural surface was prepared on the Ti-6Al-4V substrate by an atmospheric plasma-spraying technique, and its microstructure and composition, as well as mechanical and biological properties, were investigated to explore potential application as a bioactive coating on bone implants. X-ray diffraction, transmission electron microscopy, scanning electron microscopy and Raman spectroscopy revealed that the zirconia coating was composed of monoclinic zirconia which was stable at low temperature, and its surface consists of nano-size grains 30-50 nm in size. The bond strength between the coating and the Ti-6Al-4V substrate was 48.4 + or - 6.1 MPa, which is higher than that of plasma-sprayed HA coatings. Hydrothermal experiments indicated that the coating was stable in a water environment and the phase composition and Vickers hardness were independent of the hydrothermal treatment time. Bone-like apatite is observed to precipitate on the surface of the coating after soaking in simulated body fluid for 6 days, indicating excellent bioactivity in vitro. The nanostructured surface composed of monoclinic zirconia is believed to be crucial to its bioactivity. Morphological observation and the cell proliferation test demonstrated that osteoblast-like MG63 cells could attach to, adhere to and proliferate well on the surface of the monoclinic zirconia coating, suggesting possible applications in hard tissue replacements.