Bone-like Apatite Research Articles

Corrosion resistance and bioactivity of SiO2-Y2O3 coatings deposited on 316L steel

Ceramic coatings consisting of SiO2-Y2O3 layers were deposited on 316L steel using the sol-gel technique. The Y2O3 layer was included to increase the build-up of apatite ceramic, and to improve the corrosion resistance of the steel to bodily fluids. Raman spectra and EDS analysis confirmed the increased presence of Ca and P on the surface of the samples after 220 days of exposure to simulated body fluid (SBF) when compared to three-layer SiO2 coatings. The nucleation of bone-like apatites on the coating surface is indicative of the bioactive effect of the Y2O3 layer. The high corrosion resistance of steel coated with Y2O3 and SiO2-Y2O3 layers was confirmed by the corrosion current densities and ICP-OES analysis of the SBF composition after exposure of the samples.

Improving Hydrophilicity and Inducing Bone-Like Apatite Formation on PPBES by Polydopamine Coating for Biomedical Application.

Copoly(phthalazinone biphenyl ether sulfone) (PPBES) as a commercially available polyarylether is a promising orthopaedic implant material because its mechanical properties are similar to bone. However, the bioinert surface of polyarylether causes some clinical problems after implantation, which limits its application as an implant material. In this study, the surface of PPBES was modified by a biomineralization method of polydopamine-assisted hydroxyapatite formation (pHAF) to enhance its cytocompatibility. Polydopamine (PDA) coating, inspired by the adhesion mechanism of mussels, can readily endow PPBES with high hydrophilicity and the ability to integrate via the bone-like apatite coating. PPBES and PDA-coated PPBES were evaluated by scanning electronic microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and contact angle measurement. The water contact angles were reduced significantly after coating with PDA. PDA was successfully synthesized on PPBES and more PDA was obtained by increasing the temperature. Bone-like apatite on PPBES (apatite-coated PPBES) was confirmed by SEM and transmission electron microscopy (TEM). The cytotoxicity of pristine PPBES and apatite-coated PPBES were characterized by culturing of NIH-3T3 cells. Bone-like apatite synthesized by pHAF could further enhance cytocompatibility in vitro. This study provides a promising alternative for biofunctionalized PPBES with improved cytocompatibility for bone implant application.

Synthesis, Corrosion and Bioactivity Evaluation of Gelatin/Silicon and Magnesium Co-Doped Fluorapatite Nanocomposite Coating Applied on AZ31 Mg Alloy

In this study, a nano-composite composed of gelatin as the matrix and Si-Mg-FA nano-particles as an additive was deposited on the AZ31 Mg alloy via dip coating method. In addition, a coating composed of MgO, MgSiO3 and Mg2SiO4 phases was applied on the AZ31 Mg alloy by anodizing process. It was found that the Nano-composite coating with a uniform distribution of nano-particles within the gelatin matrix with the thickness of about 9 µm was dense, crack-free and uniform whereas the surface of anodized layer was relatively coarse due to the presence of flaws and micro-cracks. The surface morphology, EDS analysis and FTIR results revealed the ability of nano-composite coated specimen to form the bone-like apatite. Due to the presence of aforementioned phases and special surface features, the anodized specimen possessed higher and lower corrosion resistance than uncoated and nano-composite coated specimens, respectively. The passive coating resistances (RCT) of nano-composite, anodized specimen and uncoated samples were 2164, 1449 and 1024 Ω cm2, respectively.

Ultraviolet-assisted biomimetic coating of bone-like apatite on anodised titanium for biomedical applications

Photocatalytic TiO2 layers were deposited by anodic oxidation on high purity titanium substrates followed by ultraviolet light A (UVA) irradiation in solutions of varying pH (1, 4, 7, and 11) for 12 h. Afterwards, the UVA-treated anodised titanium foils were soaked in simulated body fluid (SBF) for 7 days. The morphological, mineralogical, surface wettability, and in vitro synthesis of the anodised samples were determined. The work showed that the surface morphology and crystallinity of the anodised coating was unchanged after UVA treatment in solutions of varying pH. However, the water contact angle decreased remarkably after UVA treatment, with the sample irradiated in a solution of pH 1 showing the lowest angle (31.8°). After soaking in SBF and with UVA irradiation for 7 days, highly crystallised bone-like apatite layer fully covered the surfaces of the anodised samples. Cross-sectional images revealed that the optimal condition for UVA treatment was at pH 1 (acidic) since it resulted in the thickest layer (2.8 μm) of bone-like apatite formation after soaking in SBF. The results clearly showed that UVA irradiation assisted the growth of bone-like apatite layer on anodised surfaces.

Preparation and characterization of implanted Fe catalyst in hydroxyapatite layer for uniformly dispersion carbon nanotube growth

An effective distribution of CNT within the HA can significantly improve the reinforcing efficiency. This paper describes a pulsed electrodeposition aided injection chemical vapor deposition (ICVD) for the preparation of a carbon nanotube (CNT) reinforced hydroxyapatite (HA) composite coating. The process involved the pulsed electrodeposition of HA and Fe catalyst, followed by the in situ ICVD synthesis of CNT. The CNT formed uniform distribution within the resulting CNT reinforced HA (CNT/HA) composite coating and bonded tightly with the HA. The CNT/HA composite coating exhibited a 1.73 times higher shear bonding strength than that of the pure HA coating. Simulated body fluid (SBF) experiment results have shown that the CNT/HA composite coating induced bone-like apatite and confirmed the bioactivity of the coating. Further electro-polarization tests have shown that the catalyst Fe reduced the equilibrium potential of the CNT/HA composite coating in the SBF solution, compared with the pure HA coating.

Comparison of osteointegration property between PEKK and PEEK: Effects of surface structure and chemistry

Weak osteointegration affects the long-term stability of polyaryletherketone (PAEK) implants. Surface modification provides a potential solution to improve the osteointegration property of PAEKs. Polyetheretherketone (PEEK) and polyetherketoneketone (PEKK) are two representative PAEK materials, but the latter has more ketone groups and better potential for surface chemical modification than the former. In this work, porous PEKK (PEKK-P) and PEEK (PEEK-P) were fabricated by a porogen leaching method. The samples were treated with 80% sulfuric acid (PEKK-SP and PEEK-SP) and then simulated body fluid (SBF) incubation (PEKK-BSP and PEEK-BSP). More micropores and higher hydrophilic SO3H groups were found on PEKK-SP than PEEK-SP. Likely, more bone-like apatite crystals deposited on PEKK-BSP than PEEK-BSP. To evaluate their osteointegration properties, the samples were implanted in femoral condyle defects (Φ3 × 4 mm3) of rat models, and micro-computed tomography (μ-CT), histology and mechanical analyzes were performed on the retrieved specimens. For control groups, i.e. the dense samples (PEKK-D and PEEK-D), only a handful of bone creeping growth on the implant surface was seen on them. However, with the interconnected macropores, surface micro/nano topography and bone-like apatite, notable bone growth into the inner pores was observed on PEKK-BSP and PEEK-BSP. Furthermore, quantitative analyses confirmed that the newly formed bone in PEKK-BSP was nearly more than doubled than that in PEEK-BSP. The push-out force testing results (PEKK-D ≈ PEEK-D < PEKK-P ≈ PEEK-P < PEEK-BSP < PEKK-BSP) suggested that the surface chemical modification (sulfonation treatment followed by SBF incubation) along with build-in porous structure played more important role in enhancing the mechanical stability of both PAEK materials than just the physical structure change. Our results revealed that PEKK with more ketone groups allowed easier sulfonation and better bone-like apatite deposition than PEEK, thus endowing PEKK-BSP with better osteointegration and mechanical stability than PEEK-BSP. Therefore, surface modified PEKK could be potential candidate for spinal and orthopedic applications requiring good osteointegration property.

Effect of poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/gelatin ratios on the characteristics of biomimetic composite nanofibrous scaffolds

Biomimetic composite nanofibrous scaffolds were fabricated via the growth of calcium phosphate (CaP) crystals on electrospun poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)/gelatin (PHGE) nanofibers with different polymer ratio to mimic the composite nature of bone tissue as well as the nanoscale features of extracellular matrix (ECM). The resulting composite scaffolds exhibited three-dimensionally interconnected microporous structures. The CaP crystals were successfully formed on not only the external surface but also the interior of the scaffolds. The amount of CaP crystals fabricated and the surface roughness of the scaffolds increased with increasing the PHBV content because of the formation of bead-typed CaP aggregates. Higher amount of CaP crystals significantly accelerated the deposit rate of bone-like apatite on the surface of composite membrane. The results of cytocompatibility tests demonstrated that PHGE41 scaffold, composed of PHBV/gelatin (4:1), promoted more rapid MC3T3-E1 proliferation and differentiation compared with other scaffolds. These results suggest that the PHGE composite scaffolds are ideal biomaterials for bone tissue engineering.

Chitosan/CaCO3-silane nanocomposites: Synthesis, characterization, in vitro bioactivity and Cu(II) adsorption properties

Chitosan nanocomposites containing 2, 5, 8wt% of calcium carbonate-γ-aminopropyl triethoxy silane (CS/CC-ATS NCs) were prepared by ultrasonic irradiation. After characterizing of physicochemical properties of the obtained CS/CC-ATS NCs, their performance was evaluated for both the bone-like apatite mineralization and the removal of Cu(II). The field emission-scanning electron microscopy images from the in vitro bioactivity of the CS and the CS/CC-ATS NC 5wt% displayed that the hydroxyapatite was produced on the samples surface. However, the distribution of it on the surface of CS/CC-ATS NC 5wt% was better than the pure CS. The uptake of Cu(II) on the CS/CC-ATS NC 5wt% was studied under different adsorption conditions such as contact time, the initial concentration of metal ion and adsorbent amount. The results of isothermal adsorption of the pure CS and the CS/CC-ATS NC 5wt% were well fitted by Langmuir model for Cu(II) with adsorption capacity of 33.33 and 33.90mg·g−1, respectively. As a result, the CS/CC-ATS NC has great potencies in both the bone tissue engineering and the uptake of toxic metal from solution.

Bionanocomposite scaffolds based on chitosan-gelatin and nanodimensional bioactive glass particles: In vitro properties and in vivo bone regeneration.

Bone repair bionanocomposite scaffolds were produced by incorporating dense bioactive glass nanoparticles or mesoporous bioactive glass nanospheres into a chitosan-gelatin polymer blend. The in vitro bioactivity of the scaffolds was assessed in simulated body fluid, and cell viability and osteogenic differentiation assays were performed with dental pulp stem cells. Bone regeneration properties of the scaffold materials were in vivo assessed by using a critical-sized femoral defect model in rat. The scaffold nanocomposites showed excellent cytocompatibility and ability to accelerate the crystallization of bone-like apatite in vitro. Bionanocomposites prepared with bioactive glass nanoparticles were particularly more active to promote the osteogenic differentiation of dental pulp stem cells as judged by the higher activity of alkaline phosphatase. This result is attributed to the faster dissolution of bioactive glass nanoparticles into osteogenic ionic products compared to mesoporous bioactive glass nanospheres. In vivo experiments demonstrated that bioactive glass nanoparticles (5%)/chitosan-gelatin bionanocomposite significantly produces the highest amount of new bone (∼80%) in the defect area after eight weeks of implantation. The bone regeneration capacity exhibited by the scaffolds formulated with nanodimensional bioactive glass particles make them attractive for bone reconstruction applications.

Deposition of novel bioactive nanoflower-like sodium titanate on TiO2 coating via anodic oxidation for biomedical applications

Bioactive coatings were prepared on titanium foils using anodic oxidation at applied voltage of 350 V and current density of 70 mA·cm−2 for 10 min. New formulation of electrolyte was introduced which consist of 0.04 M β-glycerophosphate (β-GP), 0.4 M calcium acetate (CA), and 1.0 M sodium hydroxide (NaOH) with different volume fractions. The results showed that the nanoflower sodium titanate was deposited on the titanium which anodically oxidised in electrolyte containing 50 vol% of β-GP + CA and 50 vol% NaOH. After soaking in SBF for 7 days, highly crystalline bone-like apatite was fully covered on surface of that particular sample.

Nanostructured amorphous magnesium phosphate/poly (lactic acid) composite coating for enhanced corrosion resistance and bioactivity of biodegradable AZ31 magnesium alloy

Due to the combination many interesting properties, magnesium alloys have attracted considerable interest as suitable metallic biomaterials for bioresorbable orthopedic implants. Nevertheless, their fast degradation in physiological environments pose challenge for their practical applications. Here, we report that spin coating of composites of nano amorphous magnesium phosphate (nAMP) and poly (lactic acid) (PLA) on AZ31 magnesium alloy. The idea is to use the nAMP/PLA composite film while tailoring the degradation and enhancing the bioactivity of magnesium alloys. SEM examinations show that as-deposited nAMP/PLA film is smooth, crack-free and the nAMP particles are well distributed in PLA matrix. The electrochemical test including potentiodynamic polarization and EIS associated with immersion test results reveal that the corrosion activities of nAMP/PLA coated AZ31 magnesium alloy in SBF are markedly suppressed. Furthermore, it is seen that massive bone-like apatite precipitates formed on surface of nAMP/PLA coated sample, which is indicative for the superior biomineralization capability achieved by nAMP/PLA nanocomposite coating. Thus, the nAMP/PLA composite coating has great potential to be employed as the protective and bioactive coating on biodegradable magnesium alloys for orthopedic applications.

Bone-Like Apatite Formation on the Plasma Electrolytic Oxidation-Treated Ti-6Al-4V Alloy in Solution Containing Si and Mg Ions.

The bon-like apatite formation on the plasma electrolytic oxidation (PEO)-treated Ti-6Al-4V alloy in solution containing Si and Mg ions was studied using various experimental techniques. A Ti-6Al-4V ELI disk and implant was used as a substrate for PEO. A pulsed DC power supply was used to apply a potential of 280 V in the electrolyte for 3 min. To examine the bioactivity, the PEO films formed implant specimens were immersed in a simulated body fluid (SBF) for 12 h. PEO-treated surface has large micro-pores and small micro-pores, and 5 Mg/Si and 20 Mg/Si coated surfaces showed the more small micro-pores than that of CaP coated surface. The peaks of the anatase and the hydroxyapatite phases after SBF immersion shifted to the left as compared to before SBF immersion. Numbers of cells increased, as Mg content increased on the PEO treated surface. Bone-like apatite is well formed on the Mg and Si contained surface.

Pore Shape Changes and Apatite Formation on Zn and Si Ion-Doped HA Films of Ti-6Al-4V After Plasma Electrolytic Oxidation Treatment.

In this study, pore shape changes and apatite formation on zinc (Zn) and silicon (Si) ion-doped hydroxyapatite (HA) films of Ti-6Al-4V by plasma electrolytic oxidation (PEO) treatment has been investigated by several techniques. The PEO films and the Ti-6Al-4V surface after immersion in SBF were observed by X-ray spectroscopy, field-emission scanning electron microscopy, and energy dispersive X-ray spectroscopy. The number of pores decreased as Zn ion concentration increased from 5Zn to 10Zn. The maximum size of pores were increased from 5Zn to 20Zn concentration, whereas, the minimum size of pores decreased. The amount of bone-like apatite formation for the 5Zn/5Si sample was higher than those of other samples immersed in SBF.

Microporous Organic-Inorganic Nanocomposite Coatings on Stainless Steel via Electrophoretic Deposition for Biomedical Applications

Microporous organic-inorganic nanocomposite coatings (chitosan/gelatin/halloysite) were deposited on stainless steel for improving the surface biocompatibility providing enhanced functionality for biomedical applications. For fabricating the coating, chitosan and gelatin-based suspensions were prepared and then dissolved in hydrochloric acid (HCl) solution; to this, varying amounts of halloysite nanotubes were added. The electrophoretic deposition (EPD) method was used at room temperature with low applied voltages (5 and 10 V) and short deposition times (1-5 minutes). Microporous coatings were characterised using optical microscopy, field emission scanning electron microscopy and energy-dispersive X-ray spectrometry. In vitro studies were performed in simulated body fluid (SBF) for 3 days to evaluate the formation of bone-like apatite on the coating surface. The extent of porosity increased with increase in the applied voltage owing to the occurrence of bubbles at the interface between the suspension and substrate.

Incorporation of Calcium Sulfate Dihydrate into Hydroxyapatite Microspheres To Improve the Release of Bone Morphogenetic Protein-2 and Accelerate Bone Regeneration.

In this study, hydroxyapatite (HA)-based microspheres with the ability to deliver bone morphogenetic protein-2 (BMP-2) were developed for accelerating bone regeneration. The incorporation of calcium sulfate dihydrate (CSD) in the HA matrix improved the rate of BMP-2 release from the microspheres. Under physiological conditions, the CSD fully degraded within 7 days and generated pore channels in the microspheres. The porosity and pore size of the HA-CSD microspheres after CSD degradation were 34.3% ± 4.2% and 11.5 ± 2.4 μm, respectively, significantly larger than those of the HA microspheres (23.9% ± 3.1% and 8.7 ± 0.9 μm, respectively). The increased porosity directly affected the rate of BMP-2 release from the microspheres. An in vitro experiment showed that both the BMP-2 release rate and the total amount of BMP-2 released increased considerably when incorporating the HA microspheres with CSD. BMP-2 was released slowly from the HA microspheres for up to 6 weeks. BMP-2 release was notably improved in the HA-CSD biphasic microspheres compared to the microspheres without CSD; the rate of release was 2.4-times faster due to the pores created by CSD dissolution after 7 days. Prior to animal testing, in vitro cell tests were performed to evaluate the biocompatibility of the HA-CSD microspheres. During CSD dissolution, biocompatible bone-like apatite precipitated on the cell surfaces, and preosteoblasts grew on the microspheres. In vivo experiments using a rabbit lateral femoral condyle defect model demonstrated that the level of bone regeneration was significantly enhanced by mineralization on the surface, generated additional pores as well as improved BMP-2 release behavior. The HA-CSD microspheres accelerated new bone growth to fill the entire defect in 6 weeks, corresponding to a 170% improvement in performance compared to the HA microspheres.

Zinc-doped Calcium Phosphate Coating on Titanium Surface Using Ostrich Eggshell as a Ca2+ Ions Source

Natural calcium source materials can be thermochemically processed and directly transformed into hydroxyapatite. In this work, ostrich eggshell was used as Ca2+ ions source in the preparation of zinc-calcium phosphate coatings on Ti substrates promoted by a two-step deposition method. The obtained coatings were characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy with field emission gun (FEG-SEM), bioactivity using McCoy medium and toxicity with chicken embryo chorioallantoic membrane (CAM). The results showed the presence of Znbrushite and Zn-hydroxyapatite as coating phases. Bioactivity was observed in all samples showing bone-like apatite on their surface. The toxicity test showed inflammatory response between mild to moderate confirming the material’s biocompatibility. The use of ostrich eggshells was shown to be effective as a Ca2+ ions source to obtain zinc-containing hydroxyapatite coatings on Ti substrates.

Bioactivity Assessment of Ag-HA

Cell culture medium has been used as an alternative to Kokubo’s solution in order to approach in vitro to in vivo bioactivity assessment. Moreover, the production of biomaterials with silver ions (Ag) has shown an antimicrobial effect and these are potential graft materials to prevent or reduce bacterial infection. In the present study, synthesis of hydroxyapatite (HA) and silverdoped hydroxyapatite (Ag-HA) with 0.13 mol% Ag (mol Ca:Ag) were performed and the bioactivity assessment was analyzed by scanning electron microscopy with field emission gun (FEG-SEM). The Ag-HA samples showed discrete bone-like apatite formation, indicating bioactivity behavior after in vitro incubation in McCoy cell culture medium after 7 days. Silver introduction into hydroxyapatite structure showed to be effective to produce a bioceramic with potential antibacterial effect and bioactivity.

Electrochemical Behavior in Simulated Physiological Solution of Ti-Nb-Zr-Calcium Pyrophosphate Composite with Enhanced Bioactivity by Spark Plasma Sintering

The potential biomedical application near β-type Ti-35Nb-7Zr alloy with different CPP ceramic additions were evaluated in vitro using electrochemical method and osteoblasts co-cultured. A small amount addition of calcium pyrophosphate (CPP) ceramic induced the formation of oxide film on the surface of the composites that can withstand passive layer breakdown and the onset of localized forms of corrosion. But localized breakdown of the oxide layer occurred on composites as the CPP exceeded 20 wt%. Ti-35Nb-7Zr-10CPP exhibits a wide passive range in the polarization curve and gets a higher potential for inducing growth of bone-like apatite and proliferation of osteoblasts on its surface compared to that of the Ti-35Nb-7Zr, CP Ti and Ti6Al4V (TC4) alloys. The favorable cell viability and growth inside the pores of the composites arise from the rough micro-porous surface and the release of bioactive metal-ceramic phase ions into the physiological environment.

Stabilization of Ca-deficient hydroxyapatite in biphasic calcium phosphate ceramics by adding alginate to enhance their biological performances.

It is of significance to further improve the bioactivity of existing calcium phosphate (Ca-P) biomaterials to satisfy the needs of regenerative medicine. Due to its compositional similarity to natural bone mineral, calcium-deficient hydroxyapatite (CDHA) is supposed to possess excellent bioactivity. However, it is difficult to fabricate Ca-P ceramics with a high amount of CDHA, as CDHA is easy to decompose during the sintering process. The present study introduced an effective approach to stabilize CDHA in biphasic calcium phosphate (BCP) ceramics by adding alginate, and investigated the roles of CDHA in their biological performances. The characterization of the phase composition, crystal structure, and functional group demonstrated that the addition of alginate could obviously inhibit CDHA decomposition to attain novel BCP ceramics with a high CDHA content (BCP-A), which could better mimic the inorganic composition of natural bones as compared with the conventional BCP ones (BCP-C). In vitro studies suggested BCP-A showed better bioactivity and osteoinductive capacity than BCP-C, as evidenced by the increased serum protein adsorption, better bone-like apatite formation and cell spreading, and promoted osteogenic differentiation. In vivo intramuscular implantation further confirmed that BCP-A could induce more ectopic bone formation than BCP-C, suggesting BCP-A had a stronger osteoinductivity. Altogether, this study demonstrates that the stabilization of CDHA in BCP ceramics by adding alginate offers a promising principle for designing regenerative biomaterials to process superior biological performances.

Preparation and cytological study of collagen/nano-hydroxyapatite/graphene oxide composites.

Biomimetic mineralized composite scaffolds are widely used as natural bone substitute materials in tissue engineering by inducing and assembling bonelike apatite. In this study, the single lamellar structure of graphene oxide (GO) powder was prepared via an improved Hummers' method. To better mimic natural bone, the collagen (COL)/Nano-hydroxyapatite (nHA)/graphene oxide (GO) composite material was prepared by simulated body fluid (SBF) method using COL/GO as a matrix template. Hydroxyapatite (HA) with calcium ion deficiency was achieved via biomimetic mineralization, and it had properties closer to those of natural bone than pure HA has. The mineralized COL/nHA/GO composites exhibited loose porous structures, and the connectivity of the holes was good and thus beneficial to the exchange of nutrients and excreted metabolites. Conculsions: Antibacterial and MTT experiment confirmed that the COL/nHA/GO composite material had excellent antibacterial property and biocompatibility. Hence, these results strongly suggested the mineralized COL/nHA/GO composite is a good candidate biomaterial to be applied in bone tissue engineering.