Immersion Tests In Simulated Body Fluid Research Articles

Duplex Fluorinated and Atomic Layer Deposition-Derived ZrO2 Coatings Improve the Corrosion Resistance and Mechanical Properties of Mg-2Zn-0.46Y-0.5Nd (wt.%) Alloy Plates and Screws.

This study investigated the corrosion resistance and mechanical properties of Mg-2Zn-0.46Y-0.5Nd (wt.%) alloy plates and screws with fluorinated coatings and atomic layer deposition (ALD)-derived zirconia (ZrO2) coatings in vitro under physiological stress conditions. Synthetic polyurethane hemimandible replicas were split and fixed as the following three groups of magnesium alloy plates and screws: no additional surface coating treatment (Group A), with fluorinated coatings (Group B), and with duplex fluorinated and ALD-derived 100 nm ZrO2 coatings (Group C). A circulating stress of 1-10 N was applied to the distal bone segment, and a 4-week simulated body fluid immersion test was employed to study the remaining material volume and the mechanical properties of the different groups. Compared with Group A and Group B, the degradation rate of magnesium alloy plates and screws' head regions was significantly slowed down under the protection of duplex MgF2/ZrO2 coatings (p < 0.01). There was no significant difference in the degradation rate of the screw shaft region between groups (p = 0.077). In contrast to fluoride coatings, duplex MgF2/ZrO2 coatings maintained the mechanical strength of magnesium alloy plates and screws after a 14 day in vitro SBF immersion test. We conclude that duplex MgF2/ZrO2 coatings exhibited a certain protective effect on the Mg alloy plates and screws under physiological stress conditions.

Studying the electrical, mechanical, and biological properties of BCZT-HA composites.

The piezoelectric properties of natural bone and their influence on bone growth have inspired researchers to study a range of bio-piezoelectric composite materials. By exploring these materials, researchers aim to understand better, how piezoelectricity can be controlled to promote bone growth and tissue regeneration. In this work, the prominent piezoelectric material, (Ba, Zr) TiO3 -x(Ba,Ca)TiO3 , abbreviated as BCZT, was selected as a possible bone growth enhancer in hydroxyapatite (HA) scaffolds. Initially, BCZT and hydroxyapatite (HA) powders were synthesized using the sol-gel method. Subsequently, various composite samples of BCZT-xHA were prepared using the conventional solid-state method. After sintering the samples at 1300°C, the phase structure, microstructure, density, and electrical properties were characterized. The samples' compressive strength was determined by analyzing the outcomes of basic compression tests. The biological behavior of the samples in terms of in vitro simulated body fluid immersion and MTT tests were evaluated. Our results revealed that among the BCZT-xHA samples, the BCZT-20HA sample had the best composition, considering its electrical, mechanical, and biological properties. A d33 value of 10 pC/N, dielectric permittivity of 110, and the g33 equal to 10.27 mV m/N resulted in the output voltage of 1.03 V. The results of the MTT assay test confirmed the noncytotoxic nature of the samples with the highest optical density in the BCZT-20HA sample.

Structural and biological analysis of Zn–Cu based biodegradable alloys for orthopedic application

This study focuses on the structural and biological analysis of Zn–Cu based biodegradable alloys for orthopedic applications. Five samples of Zn–Cu based alloys were prepared using a solid-state method at a temperature of 750 °C. X-ray diffraction (XRD) analysis revealed that all samples predominantly exhibited the single phase of Cu5Zn8 with minor peaks of Zn,Fe and Mg.SEM/EDX results shows the coral-like structure with grain size of 160 nm in all samples. The electrical conductivity of the alloys was evaluated through a four-probe analysis, and ZnCu0.5Fe0.4 exhibited the highest electric stimulation (1.5 × 108 S/m) can promote bone growth and aid in the healing process. Optical studies of the Zn–Cu based alloys showed absorption peaks in the range of (335–525) nm, with ZnCu0.5Fe0.4 exhibiting the lowest band gap energy (5.25 eV). The biocompatibility of the alloys was assessed through a simulated body fluid (SBF) immersion test, which indicated that all samples demonstrated biocompatible behavior. ZnCu0.5Mg0.4 exhibited the lowest corrosion rate (0.09 mm/year). Fourier-transform infrared spectroscopy (FTIR) confirmed the presence of the Cu5Zn8 phase and the formation of hydroxyapatite after in vivo testing in all samples. The electrochemical analysis demonstrated the degradation behavior of all samples, with ZnCu0.5Mg0.4 exhibiting the highest corrosion potential (−0.28 V) and improved corrosion resistance compared to the other alloys.

Preparation and mechanical and biological performance of the Sr-containing microarc oxidation layer on titanium implants

A Strontium-doped titanium oxide coating was successfully prepared on a TA4 substrate with one-step microarc oxidation (MAO) technology. Then bioactivity of the coating was performed with the inducation test of bone-like apatite formation immersed in simulated body fluid (SBF). The biological activity of the coating was evaluated with cell culture experiments, and its corrosion resistance was characterized with electrochemical tests in the SBF. The composition and morphology of the coatings before and after SBF immersion were characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The results showed that the coating had a rough porous structure, which was mainly composed of anatase, rutile and Ti phases. The SBF immersion test showed that abundant 3D micro nanopore structures were formed on the surface of the porous titanium oxide coatings, which enabled the coatings to exhibit good apatite nucleation ability. Faster precipitation of bone-like apatite by MAO-Sr coatings in SBF. Finally, in the biological compatibility test, compared with TA4, the contact angle between the MAO-Sr coating and SBF solution was lower, and the proliferation ability of bone marrow stromal cells (BMSCs) in the biological coating was stronger, indicating the good biocompatibility of the coating.

Novel Bioactive Magnesium-Hopeite composite by friction stir processing for orthopedic implant applications

Magnesium (Mg) shows excellent potential for orthopedic implant applications owing to its equivalent mechanical properties compared to cortical bone and its biocompatibility. However, the rapid degradation rate of magnesium and its alloys in the physiological environment results in losing their mechanical integrity before complete bone healing. In light of this, friction stir processing (FSP), a solid-state process, is used to fabricate Hopeite (Zn(PO4)2.4H2O) reinforced novel magnesium composite. As a result of the novel composite fabricated by FSP, grain refinement of the matrix phase occurs significantly. The samples were immersed in simulated body fluid (SBF) for in-vitro bioactivity and biodegradability tests. The corrosion behavior of pure Mg, FSP Mg, and FSP Mg-Hopeite composite samples was compared using electrochemical and immersion tests in SBF. It found that Mg-Hopeite composite has better corrosion resistance than FSP Mg and pure Mg. Because of grain refinement and the presence of secondary phase Hopeite in the composite, the mechanical properties and corrosion resistance improved. The bioactivity test was performed in the SBF environment, and a rapid apatite layer was formed on the surface of Mg-Hopeite composite samples during the test. Osteoblast-like MG63 cells were exposed to samples, and the MTT assay confirmed the non-toxicity of the FSP Mg-Hopeite composite. The wettability of the Mg-Hopeite composite was improved than pure Mg. The present research findings showed that the novel Mg-Hopeite composite fabricated by FSP is a promising candidate for orthopedic implant applications, unreported in the literature.

Microstructural evolution and biological properties of PEO coating on SLM-prepared NiTi alloy

Selective laser melting (SLM)-prepared NiTi alloy is considered to have great application potential in the fabrication of complex-structured metal implant materials. However, the SLM-NiTi alloy still suffers from some disadvantages, such as poor bio-corrosion resistance, bio-compatibility, and health hazards caused by the release of nickel ions. In order to improve the surface biological properties of SLM-NiTi alloys, bio-active coatings rich in Ca and P elements were prepared on SLM-NiTi alloys by PEO process in this work. Confocal laser scanning microscopy, SEM, EDX, XRD, and XPS were utilized to feature the micro-structure, thickness, element information, and composition of SLM/PEO coatings at different oxidation times. The adhesion strength was determined using scratch testing. A potential polarization test and a simulated body fluid (SBF) immersion test were applied to assess the corrosion resistance and detect the biological activity of SLM/PEO coatings at varied oxidation periods, respectively. The results showed that the growth of SLM/PEO coatings was hindered due to the overflow of Ni elements at the spark discharge stage (stage II). However, with the PEO process, the inhibition effect of Ni element was gradually eliminated. The pore size, thickness and the TiO2 rutile phase content of the SLM/PEO coatings gradually increased over time. However, the coating density, roughness and adhesion strength increased first and then decreased, and the SLM/PEO coatings were maximized at 15 min. The main composition of SLM/PEO coatings was TiO2, CaO, CaHPO4 and Ca3(PO4)2, and hydroxyapatite (HA) was gradually formed in the coating with time. The SLM/PEO-15 min coating with high thicknesses and rutile phase content, as well as optimum density provided optimum corrosion resistance (1.615 × 10−6 A cm−2). Meanwhile, the SLM/PEO-15 min coating possessed the best surface roughness and higher active element content, providing an excellent nucleation point and growth environment for the deposition of apatite. And the Ni element on the SLM-NiTi alloy substrate surface (oxidation time from 0 to 20 min) was significantly reduced from 12.49 % to 0.52 % after immersing in SBF solution for 24 h. Therefore, the PEO process can effectively improve the corrosion resistance and biological activity of SLM-NiTi alloy and inhibit the release of Ni elements.

Biomechanics and Surface Activity in Simulated Body Fluid of Antibiotic Intramedullary Nail

Intramedullary nail continues to evolve with the introduction of new technologies as it is considered a gold standard in treating bone defects caused by disease, trauma and accidents which are evidently higher in developing countries like the Philippines. Recently, Philippine Orthopedic Center introduced the usage of Antibiotic Intramedullary Nails (ABIMN), a threaded stainless rod coated with antibiotic cement to treat infections that commonly occurs in bone defects. The product has been widely used, however, no biomechanical study was made to demonstrate and test the coronal bending, cyclic axial loading and chemical properties of the ABIMN. The researchers compared the biomechanical properties and surface activity when immersed in Simulated Body Fluid (SBF) of the Antibiotic Intramedullary Nail (ABIMN), Küntscher Intramedullary Nail (KIMN), and Intramedullary Nail with Interlocking screws (IMNIS). A total of 37 Intramedullary Nail (IMN) models were used for the biomechanical study, while the 4 remaining nails were used for the SBF immersion test. A very high positive correlation between bending rigidity and radius to the 4th power in ABIMN was found. Median Young’s modulus of elasticity on the other hand, significantly differs across the three groups. Further analysis showed that the median value was significantly lower in ABIMN compared to KIMN (p=0.0027) and IMNIS (p=0.0025) concluding that the ABIMN can be left for 6 weeks, with the patient on partial weight bearing up to 25% of an average 75kg man. The chemical properties of the ABIMN however, revealed that it is safe to use and has qualitatively comparable corrosion properties of KIMN when immersed in SBF. For easier removal of the ABIMN and after completion of both oral and IV antibiotics at 6 weeks post op; it still advisable to remove the ABIMN and perform exchange nailing at the said timeframe.

Improved Osseointegration of Selective Laser Melting Titanium Implants with Unique Dual Micro/Nano-Scale Surface Topography.

Selective laser melting manufacture of patient specific Ti implants is serving as a promising approach for bone tissue engineering. The success of implantation is governed by effective osseointegration, which depends on the surface properties of implants. To improve the bioactivity and osteogenesis, the universal surface treatment for SLM-Ti implants is to remove the primitive roughness and then reengineer new roughness by various methods. In this study, the micro-sized partially melted Ti particles on the SLM-Ti surface were preserved for assembling mesoporous bioactive glass nanospheres to obtain a unique micro/nano- topography through combination of SLM manufacture and sol-gel processes. The results of simulated body fluid immersion test showed that bioactive ions (Ca, Si) can be continuously and stably released from the MBG nanospheres. The osseointegration properties of SLM-Ti samples, examined using pre-osteoblast cells, showed enhanced adhesion and osteogenic differentiation compared with commercial pure titanium commonly used as orthopedic implants. Overall, the developed approach of construction of the dual micro/nano topography generated on the SLM-Ti native surface could be critical to enhance musculoskeletal implant performance.

Characterization of Physical and Biological Properties of a Caries-Arresting Liquid Containing Copper Doped Bioglass Nanoparticles.

Silver diamine fluoride (SDF) is an outstanding dental material for arresting and preventing caries, but some drawbacks, such as high flowability due to low viscosity and cytotoxicity to the pulp, have been reported. To overcome these problems, copper-doped bioactive glass nanoparticles (CuBGns) were combined with SDF. After synthesis, CuBGns were examined by physical analysis and added in SDF at different weight/volume% (SDF@CuBGn). After assessing physical properties (viscosity and flowability) of SDF@CuBGn, physicochemical properties (morphology before and after simulated body fluid (SBF) immersion and ion release) of SDF@CuBGn-applied hydroxyapatite (HA) discs were evaluated. Biological properties were further evaluated by cytotoxicity test to pulp stem cells and antibacterial effect on cariogenic organisms (Streptococcus mutans and Staphylococcus aureus). Combining CuBGns in SDF increased the viscosity up to 3 times while lowering the flowability. More CuBGns and functional elements in SDF (Ag and F) were deposited on the HA substrate, even after SBF immersion test for 14 days, and they showed higher Cu, Ca, and Si release without changing F and Ag release. Cell viability test suggested lower cytotoxicity in SDF@CuBGn-applied HA, while CuBGns in SDF boosted antibacterial effect against S. aureus, ~27% in diameter of agar diffusion test. In conclusion, the addition of CuBGn to SDF enhances viscosity, Ag and F deposition, and antibacterial effects while reducing cell toxicity, highlighting the role of bioactive CuBGns for regulating physical and biological effects of dental materials.

A silicate-loaded MgAl LDH self-healing coating on biomedical Mg alloys for corrosion retardation and cytocompatibility enhancement

Clinical application of magnesium (Mg) alloys such as bone fracture fixation is hindered by the fast degradation rate under physiological conditions. In this work, a magnesium‑aluminum layered double hydroxide coating intercalated with silicate (LDH-SiO3) is fabricated on the anodized AZ31B Mg alloy by a hydrothermal technique and anion exchange process to tailor the corrosion rate and cytocompatibility. The LDH-SiO3 coating comprising a porous outer layer and compact inner layer adheres strongly to the anodized Mg alloy substrate. Electrochemical tests reveal that the LDH-SiO3 coating reduces the corrosion current density by 266 times to 0.8 ± 0.1 μA cm−2 in addition to yielding a large charge transfer resistance of 4.98 × 104 Ω cm2 in the simulated body fluid (SBF), revealing decreased corrosion because of inhibition of diffusion of aggressive ions through the compact and adherent inner LDH layer on the Mg alloy substrate. Immersion tests in SBF for 360 h reveal that the LDH-SiO3 coating mitigates corrosion propagation, Mg release, hydrogen evolution, and pH variation, indicating the notable long-term protection ability resulting from the self-healing LDH-SiO3 coating after localized corrosion occurs on the Mg alloy substrate. The self-healing mechanism mainly stems from SiO32− released from the LDH coating in conjunction with Mg leaching during natural degradation, resulting in the formation of Mg silicate precipitate that covers the corroded areas. Biologically, the LDH-SiO3 coating enhances attachment and proliferation of MC3T3-E1 pre-osteoblasts suggesting good cytocompatibility stemming from the favorable outcome including inhibited Mg leaching and alkalization as a result of the LDH-SiO3 coating. The self-healing LDH-SiO3 coating is very promising in expanding the clinical application of Mg-based implants by offering a viable approach to control corrosion and improve cytocompatibility.

Improvement of osseointegration of Ti\u20136Al\u20134V ELI alloy orthodontic mini-screws through anodization, cyclic pre-calcification, and heat treatments

BackgroundMini-screws are widely used as temporary anchorages in orthodontic treatment, but have the disadvantage of showing a high failure rate of about 10%. Therefore, orthodontic mini-screws should have high biocompatibility and retention. Previous studies have demonstrated that the retention of mini-screws can be improved by imparting bioactivity to the surface. The method for imparting bioactivity proposed in this paper is to sequentially perform anodization, periodic pre-calcification, and heat treatments with a Ti–6Al–4V ELI alloy mini-screw.Materials and methodsA TiO2 nanotube-structured layer was formed on the surface of the Ti–6Al–4V ELI alloy mini-screw through anodization in which a voltage of 20 V was applied to a glycerol solution containing 20 wt% H2O and 1.4 wt% NH4F for 60 min. Fine granular calcium phosphate precipitates of HA and octacalcium phosphate were generated as clusters on the surface through the cyclic pre-calcification and heat treatments. The cyclic pre-calcification treatment is a process of immersion in a 0.05 M NaH2PO4 solution and a saturated Ca(OH)2 solution at 90 °C for 1 min each.ResultsIt was confirmed that the densely structured protrusions were precipitated, and Ca and P concentrations, which bind and concentrate endogenous bone morphogenetic proteins, increased on the surface after simulated body fluid (SBF) immersion test. In addition, the removal torque of the mini-screw fixed into rabbit tibias for 4 weeks was measured to be 8.70 ± 2.60 N cm.ConclusionsA noteworthy point in this paper is that the Ca and P concentrations, which provide a scaffold suitable for endogenous bone formation, further increased over time after SBF immersion of the APH group specimens. The other point is that our mini-screws have a significantly higher removal torque compared to untreated mini-screws. These results represent that the mini-screw proposed in this paper can be used as a mini-screw for orthodontics.

Laser cladding preparation of HA-Ag gradient bioactive ceramic coating: A feasibility study

Laser cladding is one of the most potential techniques to prepare hydroxyapatite (HA) bioactive ceramic coating on titanium (Ti) surface to enhance bioactivity of orthopedic implants. However, there exists a disadvantage that HA is easy to be decomposed due to laser overheating for melting Ti metal or converted into a non-bioactive substance due to chemical reaction with Ti metal. In this paper, a novel technique for preparing a higher bioactive ceramic coating with a three-layer gradient structure on medical Ti substrate surface by wide-band laser cladding process was proposed. Firstly, a silver (Ag) barrier layer was prepared on Ti substrate by using 100 wt% Ag powder, which was used to block the diffusion of Ti element to the coating, so as to avoid the chemical reaction between HA and Ti to generate non-bioactive calcium titanate (CaTiO 3 ). Secondly, a transition layer was prepared in the middle by using the powder mixture of HA and Ag in weight ratio of 3:1 as the cladding material on the barrier layer. Finally, a HA bioactive ceramic layer was prepared on the transition layer at lower laser power density by using 100 wt% HA powder, which could help to create osseointegration between the coating and the host bone tissue. The morphology, phase compositions of the three functional layers of the HA-Ag bioactive ceramic coating were investigated, and their formation mechanisms were analyzed. The bioactivity and biocompatibility of the coating were assessed respectively by simulated body fluid (SBF) immersion test and cell culture test in vitro . The results showed that the main phase of the bioactive layer of the gradient coating was HA, which exhibited excellent bioactivity and biocompatibility. The proposed method of bioactivity modification for Ti metal implant surface is feasible, which has a good prospect for bone tissue engineering applications. • A bioactive ceramic coating with three-layer gradient structure was prepared. • The Ag barrier layer prevented Ti element in substrate from diffusing to coating. • The coating had excellent bioactivity and potential ability of osseointegration. • The coating exhibited comparable biocompatibility to medical Ti metal.

Effect of titanium dioxide intermediate layer on scratch and corrosion resistance of sol-gel-derived HA coating applied on Ti-6Al-4V substrate.

Modification of dental and orthopedic implants' surface by coating themwith bioactive materials, such as hydroxyapatite (HA), diminishes the implants' fixation time. Appropriate adhesion to the substrate and stability in biological conditions are essential requirements for these coatings. In this study, sol-gel-derived HA coating was applied on the Ti-6Al-4V substrate, which is a high-performance alloy for manufacturing bone implants. Also, titanium dioxide (TiO2) which was prepared by the sol-gel method was used as an intermediate layer between HA coating and the substrate. The nano-scratch and potentiodynamic polarization tests were employed to evaluate the effectiveness of TiO2 intermediate layer on improving the scratch resistance, as an indicator of coating adhesion strength, and the corrosion resistance of the coated samples. The quality of the coating bonded to the substrate was studied by cross-sectional SEM images. The XRD tests indicated that HA and TiO2 coatings were formed with predetermined phase compositions. The biocompatibility of sol-gel-derived HA coating was established by simulated body fluid (SBF) immersion tests. The SEM images, along with the results of electrochemical and nano-scratch tests, proved the significant effect of a TiO2 intermediate layer on improving the scratch resistance and stability of HA coating on titanium alloy substrate.

Effects of annealing on mechanical properties and degradation behavior of biodegradable JDBM magnesium alloy wires

Mg–Nd–Zn–Zr magnesium alloy (JDBM) has been studied widely as biodegradable medical material. To process high quality JDBM wires, effects of annealing on the mechanical properties and degradation behavior after drawing were studied by microscopic observations, tensile and immersion tests. The as-extruded wires with a diameter of 3 mm could be drawn up to 9 passes without annealing until 125% cumulative drawing deformation. Complete recrystallization occurred after annealing at 325 °C for 30 min, 350 °C for 5 min or 450 °C for 3 min, respectively. Room temperature tensile tests and simulated body fluid immersion tests showed that annealing at slightly elevated temperature for short time could obtain better properties due to the finer grain size and more dispersive distribution of precipitates. For this study, annealing at 350 °C for 5 min is the best parameters which can be utilized to further fabricate fine wires.

Improved in-vitro corrosion performance of titanium using a duplex system of plasma electrolytic oxidation and graphene oxide incorporated silane coatings

In this study, pure and 0.1 wt% graphene oxide (GO) incorporated silane layers were deposited on plasma electrolytic oxidation coated titanium as biocompatible sealants using the sol-gel method. Thereafter, their corrosion protection performance was investigated during 14-day in-vitro immersion. The characterization revealed that the silane layers with amorphous structure covered surficial inherent defects of plasma electrolytic oxidation coated titanium and decreased surface roughness as well as hydrophilicity. Further, the embedment of GO nanosheets improved the integrity of the silane layer and caused a reduction in work of adhesion and surface free energy. Accordingly, the chemical affinity and dissolution kinetics of plasma electrolytic oxidation coated titanium in simulated body fluid (SBF) weakened such that the polarization resistance rose to 956.33 and 2213.69 k Ω ·cm 2 after applying pure and GO incorporated silane layers, respectively. The electrochemical impedance spectroscopy demonstrated that the pure silane layer promoted the stability of the plasma electrolytic oxidation coated titanium from about 3 to 7 days. Also, the GO incorporated silane layer provided better stability to the end of 14 days and its protective performance was higher in the first 3 days. The SBF immersion test clarified that the bioactivity of the silane layers was higher than that of titanium due to the induction of particulate calcium-phosphate precipitations. • The surface roughness and hydrophilicity reduced by preparing PEO-Silane-GO. • The in-vitro corrosion stability of PEO-Silane-GO promoted upon 14 days. • The precipitated calcium-phosphate on the duplex coating system increased slightly.

3D-printed composite, calcium silicate ceramic doped with CaSO4·2H2O: Degradation performance and biocompatibility

Calcium silicate is a common implant material with excellent mechanical strength and good biological activity. In recent years, the addition of strengthening materials to calcium silicate has been proven to promote bone tissue regeneration, but its degradation properties require further improvements. In this paper, calcium silicate was used as the matrix, and 10 wt% hydroxyapatite and 10 wt% strontium phosphate were added to im prove the biological activity of the scaffold. The effect of adding different amounts of calcium sulfate dihydrate (CaSO4·2H2O) on the degradation of the scaffold was explored. A porous ceramic scaffold was prepared by digital light processing (DLP) technology, and its performance was evaluated. Cell experiments showed that the addition of calcium sulfate improved cell proliferation and differentiation. Simulated body fluid (SBF) immersion tests showed that small amounts of apatite deposits appeared on the fourth day, larger deposits appeared on the 14th day, and degradation occurred on the surface after 28 days of immersion. Mechanical tests showed that the addition of 5 wt% CaSO4·2H2O improved the compressibility of the composite. After soaking in SBF for 14 days, it retained its compressive strength (11.8 MPa), which meets the requirements of cancellous bone, demonstrating its potential application value for bone repair.

Preparation and Degradation Characteristics of MAO/APS Composite Bio-Coating in Simulated Body Fluid

In this work, ZK60 magnesium alloy was employed as a substrate material to produce ceramic coatings, containing Ca and P, by micro-arc oxidation (MAO). Atmospheric plasma spraying (APS) was used to prepare the hydroxyapatite layer (HA) on the MAO coating to obtain a composite coating for better biological activity. The coatings were examined by various means including an X-ray diffractometer, a scanning electron microscope and an energy spectrometer. Meanwhile, an electrochemical examination, immersion test and tensile test were used to evaluate the in vitro performance of the composite coatings. The results showed that the composite coating has a better corrosion resistance. In addition, this work proposed a degradation model of the composite coating in the simulated body fluid immersion test. This model explains the degradation process of the MAO/APS coating in SBF.

3D printed PEEK/HA composites for bone tissue engineering applications: Effect of material formulation on mechanical performance and bioactive potential

Polyetheretherketone (PEEK) is a biocompatible polymer widely used for biomedical applications. Because it is biologically inert, bioactive phases, such as nano-hydroxyapatite (HA), have been added to PEEK in order to improve its bioactivity. 3D printing (3DP) technologies are being increasingly used today to manufacture patient specific devices and implants. However, processing of PEEK is challenging due to its high melting point which is above 340 °C. In this study, PEEK-based filaments containing 10 wt% of pure nano-HA, strontium (Sr)- doped nano-HA and Zinc (Zn)-doped nano-HA were produced via hot-melt extrusion and subsequently 3D printed via fused deposition modelling (FDM), following an initial optimization process. The raw materials, extruded filaments and 3D printed samples were characterized in terms of physicochemical, thermal and morphological analysis. Moreover, the mechanical performance of 3D printed specimens was assessed via tensile tensing. Although an increase in the melting point and a reduction in crystallization temperature was observed with the addition of HA and doped HA to pure PEEK, there was no noticeable increase in the degree of crystallinity. Regarding the mechanical behavior, no significant differences were detected following the addition of the inorganic phases to the polymeric matrix, although a small reduction in the ultimate tensile strength (~14%) and Young's modulus (~5%) in PEEK/HA was observed in comparison to pure PEEK. Moreover, in vitro bioactivity of 3D printed samples was evaluated via a simulated body fluid immersion test for up to 28 days; the formation of apatite was observed on the surfaces of sample surfaces containing HA, SrHA and ZnHA. These results indicate the potential to produce bioactive, 3DP PEEK composites for challenging applications such as in craniofacial bone repair.

Physicochemical and Biological Properties of Mg-Doped Calcium Silicate Endodontic Cement.

Calcium silicate-based cement has been widely used for endodontic repair. However, it has a long setting time and needs to shorten setting time. This study investigated the effects of magnesium (Mg) ion on the setting reaction, mechanical properties, and biological properties of calcium silicate cement (CSC). Sol-gel route was used to synthesize Mg ion-doped calcium silicate cement. Synthesized cement was formulated with the addition of different contents of Mg ion, according to 0, 1, 3, 5 mol% of Mg ion-doped calcium silicate. The synthesized cements were characterized with X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM). We also evaluated the physicochemical and biological properties of cement, such as the setting time, compressive strength, micro-hardness, simulated body fluid (SBF) immersion, cytotoxicity, and cell differentiation tests. As a result, the Mg ion improves the hydration properties of calcium silicate cement, and the setting time is reduced by increasing the amounts of Mg ion. However, the mechanical properties deteriorated with increasing Mg ion, and 1 and 3 mol% Mg-doped calcium silicate had appropriate mechanical properties. Also, the results of biological properties such as cytotoxicity, ALP activity, and ARS staining improved with Mg ion. Consequently, the optimal condition is 3 mol% of Mg ion-doped calcium silicate (3%Mg-CSC).

Construction and Biological Performance of Surface Treated Porous Titanium Scaffold Using Nanotube Arrays of Anatase

TiO2 nanotube in diameter of ~ 100 nm array films were prepared on a porous titanium scaffold with a porosity of 70% via anodic oxidation. The morphology and phases of the films were characterized, and the thermal stability of the films were also studied. In-vitro, the bioactivity of the modified scaffolds was evaluated by simulated body fluid immersion test. In vivo, the scaffolds were implanted into the back muscles of the dog for 6 months. Results show that the anatase nanotubues give better bioactivity than the amorphous. The scaffold after anodic oxidation and annealing at 500 °C for 5 hours not only can induce the formation of hydroxyapatite, but also can induce blood vessel formation and promote the expressions of bone morphogenetic protein BMP-2. The BMP-2 concentrations is 5.57±0.20 μ/L for the scaffold been anodically oxidated and heat-preserved, the value is much higher than that of untreated scaffold(2.78±0.16 μg/L)or only been anodically oxidated(2.86±0.17 μg/L). It shows that the anatase TiO2 nanotubes can contribute to the potential osteoinductivity. This study will promote the development of novel functional porous supports.