Applications In Hard Tissue Replacements Research Articles

Microstructure and Elastic Properties of Hydroxyapatite/Alumina Nanocomposites Prepared by Mechanical Alloying Technique for Biomedical Applications

Although hydroxyapatite (HA) has exceptional biological qualities that inspire researchers to employ it as an appealing biomaterial for various purposes, its usage in hard tissue replacement applications is severely restricted because of its fragility. In order to create nanocomposites with the necessary mechanical properties for biomedical applications, HA was produced, and various amounts of alumina (Al2O3) were added to it. Additionally, the phase composition of the powdered nanocomposites was examined using the X-ray diffraction (XRD) technique. Crystal sizes, lattice strain, and dislocation density were all estimated as well. In order to measure the produced nanocomposite powders’ physical and elastic characteristics using the Archimedes method and ultrasonic non-destructive technique, they were then pressed and sintered at 1000 °C. The resulting information made it clear that further increases in the weight percentages of Al2O3 resulted in a 10.25, 25.64, and 33.33% reduction in crystal size. As a result of adding more Al2O3-up to 20 weight, percent-the results also showed that this properties-microhardness, compressive strength, Young’s modulus, elastic modulus, bulk modulus, shear modulus, and Poisson’s ratio-were improved by 109, 36.29, 95.5, 100.59, 104.97, 92.84 and 9.5%, respectively. Unfortunately, it increased its porosity by considerable amounts. It might be argued that the generated nanocomposites are favorable for biomedical applications.

A novel multi-structural reinforced treatment on Ti implant utilizing a combination of alkali solution and bioactive glass sol

ObjectiveAlkali treatment and bioactive glass (BG) sol dip-coating are well-known individual methods for titanium (Ti) surface modification. In this study, a unique combination of alkali treatment and bioactive glass sol dip coating was applied to the Ti substrate, then the mechanical properties and cell responses were investigated. MethodsBased on the methods introduced above, the Ti substrate was treated by 6 mL of an NaOH 5 M aqueous solution for 24 h at 60 ̊C; this was followed by adding 1.2 mL of a BG 58S sol to form a novel combined nanostructure network covered by a thin BG layer. For the assessment of the formed coating layer, the morphology, elemental analysis, phase structure, adhesion property and the cell response of the untreated and treated surfaces were investigated. ResultsThe BG coating layer was reinforced by the nanostructure, fabricated through the alkali treatment. The results obtained by applying the combined modification method confirmed that the mechanical and biological properties of the fabricated surface demonstrated the highest performance compared to that of the unmodified and individually modified surfaces. SignificanceThe achieved upgrades for this method could be gained from the demanded porous nanostructure and the apatite transformation ability of the alkali treatment. Therefore, the hybridized application of the alkali-BG treatment could be introduced as a promising surface modification strategy for hard-tissue replacement applications.

Comparison of template mediated ultrasonic and microwave irradiation method on the synthesis of hydroxyapatite nanoparticles for biomedical applications

We have reported a template directed synthesis of hydroxyapatite nanoparticles from CaCl2·2H2O and (NH4)2HPO4 as calcium and phosphate precursors respectively, by ultrasonic irradiation method. The effect of template tryptophan addition, the influence of microwave irradiation and ultrasonic irradiation on the purity, structural and morphological properties of hydroxyapatite nanoparticles were investigated during its synthesis. FT-IR and XRD analysis were carried out to identify the phase and the purity of the as-synthesized nanoparticles and the results eventually claimed that the formation of hydroxyapatite in all synthesis conditions. Moreover, it is evident that microwave as well as the ultrasonic irradiation method is rapid synthesis routes for HAP when compared to conventional heating method with and without template addition. But the morphological evaluation using SEM and TEM analysis clearly emphasized that the combination of template tryptophan with the Ca/P precursors and the assistance of microwave /ultrasound irradiation can effectively regulate and reduce the size of the hydroxyapatite nanoparticles. Particularly, the application of an ultrasound irradiation during the synthesis of HAP facilitates the size of the nanoparticles below 30 nm with uniform cylindrical morphology. Hence, the HAP nanoparticles synthesized by template directed ultrasonic irradiation method can act as a better biomaterial for hard tissue replacement applications.

Nano-tribological behavior of graphene nanoplatelet–reinforced magnesium matrix nanocomposites

Abstract The corrosion resistance and wear resistance of metallic biomaterials are critically important for orthopedic hard-tissue replacement applications because the lack of such properties not only adversely affects their mechanical integrity but also allows the release of wear debris into the human body. In this study, the potential of zirconium (Zr) as an alloying element and graphene nanoplatelets (GNPs) as a nano-reinforcement material were investigated in relation to improving the tribological performance of pure magnesium (Mg). The GNPs–reinforced Mg matrix nanocomposites (MNCs) were fabricated using powder metallurgy. Results indicate that additions of 0.5 wt.% Zr and 0.1 wt.% GNPs to Mg matrices significantly improved the wear resistance by 89% and 92% at 200 µN load, 60% and 80% at 100 µN load, and 94% and 93% at 50 µN load, respectively, as compared to the wear resistance of pure Mg. The wear depth and coefficient of friction of the MNC containing 0.5 wt.% Zr and 0.1 wt.% GNPs (Mg0.5Zr0.1GNPs MNC) were considerably reduced as compared to pure Mg and Mg0.5Zr. Our results demonstrate that the Mg0.5Zr0.1GNPs MNC is promising for orthopedic applications in relation to its excellent tribological performance.

Surface modification of Ti-6Al-4V alloy for osseointegration by alkaline treatment and chitosan-matrix glass-reinforced nanocomposite coating

Individual and combined treatments of alkaline (NaOH) and chitosan/bioactive glass (SiO2-CaO-MgO) nanocomposite coating were applied on Ti-6Al-4V alloy surfaces with the objective of investigating and improving i) wettability, ii) apatite-formation ability, iii) corrosion resistance, and iv) biocompatibility. Individual applications of each surface treatment were found to enhance hydrophilicity, apatite-forming ability, corrosion resistance, and cytocompatibility (MG-63 cells). The most improved properties, except apatite-formation ability, were obtained using the combined treatment yielding a reduction of 64 and 93% in sessile contact angle and corrosion rate, respectively, than the untreated substrate. These improvements originate from the desired roughness and apatite-formation ability of the alkaline treatment and the appropriate biocompatibility and corrosion protection of the nanocomposite coating. That is, the combined application of alkaline treatment and chitosan nanocomposite coating is demonstrated as a promising surface-engineering strategy for hard-tissue replacement applications.

Structural Perceptions and Mechanical Evaluation of β-Ca3(PO4)2/c-CeO2 Composites with Preferential Occupancy of Ce3+ and Ce4.

The role of cerium in the formation of stable β-Ca3(PO4)2/c-CeO2 composites and their structural analysis with varied compositional ratios were investigated. The composite formation was attempted through an in situ precipitation technique, and the gradual structural changes during heat treatments to yield the pure form of β-Ca3(PO4)2/c-CeO2 composites was presented. The cerium was found in Ce3+ and Ce4+ oxidation states in composites. Ce3+ prefers to occupy the Ca2+(1), Ca2+(2), and Ca2+(3) sites of β-Ca3(PO4)2, whereas, beyond the saturation occupancy limit, excess cerium prefers to crystallize in the form of thermodynamically stable cubic ceria (c-CeO2). A uniform expansion of the β-Ca3(PO4)2 unit cell and the delayed allotropic conversion of β-Ca3(PO4)2 → α-Ca3(PO4)2 have been detected due to the Ce3+ occupancy at the β-Ca3(PO4)2 lattice. β-Ca3(PO4)2/c-CeO2 composites exhibited a steady upsurge in the mechanical properties with consistent enhancement of c-CeO2 content in the composites. The overall results from the investigation imply the appropriateness of the β-Ca3(PO4)2/c-CeO2 composites for applications in hard tissue replacements.

Deposition, structure, physical and invitro characteristics of Ag-doped β-Ca3(PO4)2/chitosan hybrid composite coatings on Titanium metal

Pure and five silver-doped (0-5Ag) β-tricalcium phosphate [β-TCP, β-Ca3(PO4)2]/chitosan composite coatings were deposited on Titanium (Ti) substrates and their properties that are relevant for applications in hard tissue replacements were assessed. Silver, β-TCP and chitosan were combined to profit from their salient and complementary antibacterial and biocompatible features.The β-Ca3(PO4)2 powders were synthesized by co-precipitation. The characterization results confirmed the Ag+ occupancy at the crystal lattice of β-Ca3(PO4)2. The Ag-dopedβ-Ca3(PO4)2/chitosan composite coatings deposited by electrophoresis showed good antibacterial activity and exhibited negative cytotoxic effects towards the human osteosarcoma cell line MG-63. The morphology of the coatings was observed by SEM and their efficiency against corrosion of metallic substrates was determined through potentiodynamic polarization tests.

Multifunctional ceramic-metal biocomposites with Zinc containing antimicrobial glass coatings

A biocompatible glassy coating with a high antimicrobial activity (>3log of reduction) versus the gram-bacterium Escherichia coli has been obtained. The substrates are based on new zirconia ceramic matrix composites reinforced with biological tolerant metals (3Y-TZP/Ta and 3Y-TZP/Nb biocermets). Biocompatibility was studied using NIH-3T3-cells (mouse embryonic fibroblast) and >70% viability was found. These results open up the possibility of using these materials in large panoply in orthopaedics, dentistry and other hard tissue replacement applications where biofunctional, structural and antimicrobial properties are required.

In vitro and in vivo evaluation of a new zirconia/niobium biocermet for hard tissue replacement

Metals and ceramics are commonly used in orthopaedics, dentistry and other load bearing applications. However, the use of ceramic matrix composites reinforced with biocompatible metals for heavy load-bearing hard tissue replacement applications has not previously been reported. In order to improve the reliability and the mechanical properties of biomedical implants, new zirconia–Nb composites have been recently developed. The aim of this study was to investigate the biological tolerance of these new zirconia/Nb biocermets implants with both in vitro and in vivo approaches. At first, human bone marrow derived mesenchymal stem cells were cultured on sintered biocermet discs with polished surfaces and were compared with responses to niobium metal. In vitro, the biocermets showed no deleterious effect on cell proliferation, extra-cellular matrix production or on cell morphology. Furthermore, the biocermet showed a higher percentage of cell proliferation than Nb metal. On the other hand, the bone response to these new zirconia/Nb biocermets was studied. Cylinders of biocermets, as well as commercially Nb rod were implanted in the tibiae of New Zealand white rabbits. All the animals were euthanatized after 6 months. The specimens were processed to obtain thin ground sections. The slides were observed in normal transmitted light microscope. A newly formed bone was observed in close contact with material surfaces. No inflamed or multinucleated cells were present. This study concluded that zirconia/Nb composites are biocompatible and osteoconductive. The ceramic-metal composite has even better osteointegration ability than pure Nb. In conclusion, zirconia–Nb biocermet is suitable for heavy load-bearing hard tissue replacement from the point of view of both mechanical properties and biocompatibility.

Improved antimicrobial activity and bioactivity of porous CaP–TiO2 coating through surface nanofunctionalisation

Titanium based implant materials are confronting poor osteointergtation and bacterial infection issues when giving full play its desirable mechanical properties to hard tissue replacement applications. On the basis of plasma electrolytic oxidation (PEO) synthesised porous CaP–TiO2 coatings, which possess favourable biological performance but poor antimicrobial potential, in this work, surface nanofunctionalisation was performed using hydrothermal treatment in order to endow these coatings with antimicrobial ability. After surface nanofunctionalisation, the coatings were decorated with numerous nanoscale petal-like topography without obviously changing the original PEO synthesised porous structure and anatase titania predominant phase composition. The effects of antibacterial evaluation suggest that the nanofuntionalised CaP–TiO2 coating possessed excellent antimicrobial activity against both Escherichia coli and Staphylococcus aureus species. The antimicrobial efficacies were all close to 100% compared to untreated PEO coating. After immersion in simulated body fluid for 7 days, the hydrothermal treated coatings were fully covered by dense hydroxylapatite layers, while untreated PEO coating was not, indicating their enhanced bioactivity.

β-type Ti-10Mo-1.25Si-xZr biomaterials for applications in hard tissue replacements

In order to develop new β-type Ti-based biochemical materials, a series of Ti-10Mo-1.25Si-xZr (x=4–13) alloys were designed and prepared using vacuum arc melting method. Phase analysis and microstructural observation showed that all the as cast samples consisted of equiaxed β-Ti phase. With the increase of Zr content, the structure of grain boundary changed from semi-continuous network to denser granular, and the microstructure was refined. The solid solution effect of the β-phase stabilization elements (i.e. Mo, Zr and Si) predominantly determined the mechanical properties. These β-type Ti-10Mo-1.25Si-xZr biomaterials exhibited a good combination of high compressive strength, high yield stress, good plasticity, as well as rather low Young's modulus (in the range of 23.086GPa–32.623GPa), which may offer potential advantages in the applications in hard tissue replacements (HTRs).

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.

Tribological investigation of novel HDPE‐HAp‐Al2O3 hybrid biocomposites against steel under dry and simulated body fluid condition

Among various biocompatible polymers, polyethylene based materials have received wider attention because of its excellent stability in body fluid, inertness, and easy formability. Attempts have been made to improve their physical properties (modulus/strength) to enable them to be used as load bearing hard tissue replacement applications. Among such attempts, high density polyethylene (HDPE)-hydroxyapatite (HAp) composite (HAPEX), has already been developed for total hip replacement (THR) acetabular cup and low load bearing bone tissue replacement. In the present work, alumina has been added as a partial replacement of HAp phase to improve the mechanical and tribological properties of the HAPEX composite. In an attempt to assess the suitability of the developed composite in THR application, the tribological properties against steel counterbody under both in air and simulated body fluid (SBF), have been investigated and efforts have been made to understand the wear mechanisms. The fretting wear study indicates the possibility of achieving extremely low COF (Coefficient of Friction approximately 0.09) as well as higher wear resistance (order of 10(-6) mm(3)/N m) with the newly developed composites in SBF. A low wear depth of approximately 4.6-5.3 microm is recorded, irrespective of fretting environment. The implication of the work is that optimal and combined addition of bioactive and bioinert ceramic filler to HDPE can provide a good opportunity to obtain hybrid biocomposites with better combination of physical properties (modulus, hardness) as well as low friction and high wear resistance.

Studies on crosslinked hydroxyapatite-polyethylene composite as a bone-analogue material

The paper examines the use of different types of polymeric matrix composites in hard-tissue replacement applications. The composite samples were prepared with hydroxyapatite (HA) powder and polyethylenes of different densities. The raw material was first compounded in the extruder and the resulting composite pre-forms were compression molded into desired plates and irradiated with different doses. Modulus of elasticity in tension, tensile strength, tensile fracture strain, elongation at break and gel content were obtained for all composites. Ceramic filler distribution was investigated under scanning electron microscopy (SEM). With HA incorporated in the samples an increase in the values of Young's Modulus, (stiffness) was observed, while elongation at break decreased with the amount of filler, showing increase of brittleness. Tensile strengths at yield and at break decreased with the filler content for LD and MDPE and stayed constant for HDPE.