Bone-bonding Ability Research Articles

243 HA/β-TCP複合材料の力学的特性に及ぼす擬似体液浸漬の影響(生体・環境適合型材料の創製と特性評価(3),ものづくりにおける基礎研究と先端技術の融合)

Bioactive ceramics attracts attentions as materials of the bone implant, because their high biocompatibility. For example, hydroxyapatite (HA) has bone-bonding ability, and β-ricalcium phosphate (β-TCP) has a high bioresorbability. In this study, HA/P-TCP composites with different content of β-TCP (5,10,20wt%) were prepared by wet mixing of HA and β-TCP powder, compaction of the powders and sintering. Bending strength of HA/β-TCP composites were measured before and after soaking in the simulated body fluid (SBF) up to 4weeks. The bioactivity of HA/β-TCP composites was also evaluated by soaking in SBF up to 4weeks. It was found that the relative density decreased as content percentage of β-TCP increased. It was also found that the bending strength decreased rapidly after 1 week soaking, whereas it doesn't decrease from 2weeks to 4weeks soaking. This result suggested that the apatite layer formed on the surface in SBF reinforced the specimen in spite of the dissolution of the surface constituents.

Preliminary in vitro Study on Enhancement of Bone-like Hydroxyapatite Formation on Bio-active Titanium Alloy by Low-intensity Pulsed Ultrasound Waving for Early Bone Bonding

In this study, we investigated whether ultrasound wave stimulation could accelerate the bone-bonding ability of bio-active titanium alloy in vitro. Titanium alloy (α+β-Ti-6Al-4V) processed in chemical and heat treatments was used as a specimen, and soaked in simulated body fluid (SBF) under pulsed ultrasound wave for the planned time periods. The surface of samples was observed using scanning electron microscopy (SEM), energy dispersive spectroscopy, X-ray diffraction to assess the state of bone-like hydroxyapatite formation. SEM images showed that a richer and finer layer of bone-like hydroxyapatite covered the titanium surface in the ultrasound wave group as compared with the non-ultrasound group. The measurements of mass of specimens also indicated the efficiency of ultrasound waves for hydroxyapatite formation. These findings suggest that the nucleation and crystallization of apatite on bio-active material surfaces might be promoted by micro-moving and cavitation of low-intensity pulsed ultrasound waves. We propose that pulsed ultrasound stimulation has a great potential for further improvement of osseointegration and osteoconductivity for medical bio-active implants.

PREPARATION OF BIOACTIVE FILM ON Ti6Al4V

Titanium oxide films were prepared using an anodic oxidation method in sulfuric acid solution on the surface of Ti6Al4V alloy at room temperature. The surface energy was obtained by the measurement of contact angles and the calculation with Owens–Wendt–Kaeble's equation. Ti6Al4V with anodic film after chemical treatment with NaOH aqueous solution showed excellent apatite-forming ability and produced a compact apatite layer covering all the surface of titanium after soaking in three times concentration (SBF × 3) for three days. A bioactive titania-CaP film was obtained on Ti6Al4V . Scanning electron microscopy, X-ray diffraction and Fourier Transform Infra-Red were used to analyze composition changes of the bioactive film. It is concluded that the acceleration of the apatite nucleation on the anodized Ti6Al4V with chemical treatment in a modified simulated body fluid was attributed to the novel surface characteristics and the formation of sodium titanate hydrogel layer during chemical pretreatment. The treatment of Ti6Al4V by anodic oxidation and subsequently in NaOH is a suitable method for providing the metal implant with bone-bonding ability.

Histological and Mechanical Evaluation of the in vivo Bone-bonding Ability on the K2TinO2n+1/β-Ti Alloy as a Novel Bioactive Material

AbstractThe purpose of this study was to histologically and mechanically appraise the in vivo bone-bonding abilities of K2TinO2n+1 coated and uncoated Ti-15Mo-3Nb (TMN) implants. According to GB/T16886.6－1997 biological evaluation of medical devices Part 6:Tests for local effects after implantation, the two types of implants were implanted into the proximal metaphyses of Chinese white rabbits’ femurs for 12, 26 and 52 weeks and investigated by pushing out test, scanning electron microscopy (SEM) attached to an energy-dispersive X-ray micro-analyzer (EDX) and light microscopy. The bone-bonding abilities of the K2TinO2n+1 biocoating /Ti-15Mo-3Nb (KBT) gradient biomaterial implants were higher than those of T implants at different periods of implantation. The K2TinO2n+1 biocoating (KB) could stimulate new bone rapid formation at the early stages of implantation. And the implants with the biocoating eventually bonded to bone directly, with no intervening soft tissue layer, that was an osseocoalescence. However, the type of bone-bonding between TMN titanium alloy implants and bone was a simple osseocoaptation. The more excellent bone-bonding ability of the KBT implants should be attributed to the superficial characteristics, the bioactivity of low potassium titanate and biostability of high potassium titanate.

Effect of CeO2 addition on crystallization behavior, bioactivity and biocompatibility of potassium mica and fluorapatite based glass ceramics

The bone-bonding ability of a glass ceramic can be evaluated by using simulated body fluid (SBF). Furthermore, rat primary osteoblast cell culture is effective in collecting preliminary information for potential application of any material of organic or inorganic origin. In this study, the effect of CeO2 addition on crystallization behavior and bioactivity of potassium mica and fluorapatite based glass ceramics was investigated. Also an osteoblast cell culture model was utilized to investigate the effect of CeO2 addition on biocompatibility of potassium mica and fluorapatite based glass ceramics by using biological criteria such as cell viability, metabolic activity and nitric oxide production.

Effect of metal-ion-to-fuel ratio on the phase formation of bioceramic phosphates synthesized by self-propagating combustion

Synthetic calcium hydroxyapatite (HAP, Ca10 (PO4)6 (OH)2) is a well-known bioceramic material used in orthopedic and dental applications because of its excellent biocompatibility and bone-bonding ability due to its structural and compositional similarity to human bone. Here we report, for the first time, the synthesis of HAP by combustion employing tartaric acid as a fuel. Calcium nitrate is used as the source of calcium and diammonium hydrogen phosphate serves as the source of phosphate ions. Reaction processing parameters such as the pH, fuel-oxidant ratio and autoignition temperature are controlled and monitored. The products were characterized by powder x-ray diffraction, which revealed the formation of a hexagonal hydroxyapatite phase. Fourier transform infrared spectroscopy (FT-IR) spectra showed that the substitution of a carbonate ion occurs at the phosphate site. The morphology of the particles was imaged by scanning electron microscopy, which also revealed that the particles are of submicron size. Thermal analysis showed that the phase formation takes place at the time of combustion. Surface area and porosity analysis showed that the surface area is high and that the pores are of nanometer size. The mean grain size of the HAP powder, determined by the Debye–Scherrer formula, is in the range 20–30 nm. Chemical analyses to determine the Ca : P atomic ratio in synthesized ceramics were performed, and it was found to be 1 : 1.66.

Osteoblast response to biomimetically altered titanium surfaces

Bioinert titanium (Ti) materials are generally encapsulated by fibrous tissue after implantation into the living body. To improve the bone-bonding ability of Ti implants, we activated commercially pure titanium (cpTi) by a simple chemical pre-treatment in HCl and NaOH. Subsequently, we exposed the treated samples to simulated body fluid (SBF) for 2 (TiCT) and 14 days (TiHCA), respectively, to mimic the early stages of bone bonding and to investigate the in vitro response of osteoblasts on thus altered biomimetic surfaces. Sample surfaces were characterized by scanning electron microscopy, energy-dispersive X-ray analysis, cross-sectional transmission electron microscopy analyses, Fourier transform infrared and Raman spectroscopy. It was shown that the efflorescence consisting of sodium titanate that is present on pre-treated cpTi surfaces transformed to calcium titanate after 2 days in SBF. After 14 days in SBF a homogeneous biomimetic apatite layer precipitated. Human osteoblasts (MG-63) revealed a well spread morphology on both functionalized Ti surfaces. On TiCT, the gene expression of the differentiation proteins alkaline phosphatase (ALP) and bone sialo protein was increased after 2 days. On both TiCT and TiHCA, the collagen I and ALP expression on the protein level was enhanced at 7 and 14 days. The TiCT and the TiHCA surfaces reveal the tendency to increase the differentiated cell function of MG-63 osteoblasts. Thus, chemical pre-treatment of titanium seems to be a promising method to generate osteoconductive surfaces.

In vivoevaluation of bone-bonding ability of RGD-coated porous implant using layer-by-layer electrostatic self-assembly

RGD has been demonstrated to improve implant osseointegration. However, few studies are known about an effect of RGD coating on a bone-bonding ability of screw-shaped porous implant. The aim of this study was to investigate the effect of RGD coating using the layer-by-layer self-assembly technique on the bone-bonding ability of porous implant. 60 implants of 10 mm in length (30 control and 30 RGD-coated) were inserted into femurs of 30 rabbits and 30 implants of 8 mm in length (15 control and 15 RGD-coated) were inserted into tibias of 15 rabbits. At 4, 8, and 12 weeks post-implantation, femurs and tibias were retrieved and prepared for removal torque tests (RTQ) and histomorphometric evaluation, respectively. No differences were found in the RTQ values between two implants at 4 weeks (p = 0.932). There were statistical significances in the RTQ values at 8 and 12 weeks (p = 0.002, 0.001, respectively). New bone was formed on both implant surfaces. The bone-implant contact pattern appeared to produce a broad-based direct contact in both implants. The RGD-coated implants showed a significantly greater BIC in the threads inside the cortical bone compared with the control implants at 4, 8, and 12 weeks (p = 0.024, 0.041, 0.022, respectively). No differences were found in the bone area within the same threads between two implants at 4 weeks (p = 0.806) whereas differences were found at 8 and 12 weeks (p = 0.009, 0.031, respectively). It was concluded that RGD coating using the layer-by-layer self-assembly technique has a positive effect on the bone-bonding ability of porous implant.

Effect of surface structure on biomechanical properties and osseointegration

The purpose of this study is to improve the bone-bonding ability between titanium implants and living bone through the control of geometric design and chemical compositions of an implant surface. We compared the tissue healing response and resulting implant stability for three surface designs by characterizing the histological and mechanical properties of the healing tissue around smooth-surfaced Ti–6Al–4V (SS), CP-Ti plasma-spray-coated (PSC), alkali- and heat-treated (AHT) implants. The implants were transversely inserted into a dog thighbone and evaluated at 4, 8, and 12 weeks. Histological examination indicated that initial matrix mineralization leading to osseointegration occurred more rapidly with the AHT implant. During the 4, 8, and 12 week healing periods, new bone on the surface of AHT implant showed denser growth than that on the SS and PSC implants. The more extensive tissue integration and more rapid matrix mineralization with the AHT implant were reflected in the mechanical test data, which demonstrated superior attachment strength and interfacial stiffness for the AHT implant after healing for 4, 8 and 12 weeks of healing because of the mechanical interlocking in the micrometer sized rough surface and the large bonding area between bone and implant caused by the nanosized porous surface structure. Histological and mechanical data demonstrate that with the appropriate surface design selection, bone bone-bonding ability can be improved and can induce acceleration of the healing response, thereby improving the potential for implant osseointegration.

Bone-Bonding Ability of Anodized Titanium Plate Loaded With Hydroxyapatite Particles

ABSTRACTSubmicron-sized hydroxyapatite (HAp) particles were loaded on the titanium plate by anodic oxidation over spark discharge voltage in HAp-containing bath. The biocompatibility and bioactivity were drastically improved by HAp deposition on the anodic oxide films. The affinity with living bone was the following order: anodized titanium plate with HAp > anodized titanium plate ≫ titanium. Bone-bonding strength between HAp-loaded titanium plate and living bone after 4 weeks' implant was much higher than that of anodized titanium plate.

Evaluation of apatite-forming ability and mechanical property of pectin hydrogels

Apatite-polymer hybrids are expected as novel bone substitutes exhibiting bone-bonding ability, i.e. bioactivity, and mechanical performances analogous to those of natural bone. To fabricate such hybrids, biomimetic process has been paid much attention where bone-like apatite is deposited on organic polymers that have specific functional groups in simulated body fluid (SBF) or more concentrated solutions. Previous studies showed that carboxyl groups (-COOH) have a catalytic effect for heterogeneous apatite nucleation in SBF. In this study, we chose pectin as an organic polymer. Pectin is a natural polysaccharide containing carboxyl groups. Hydrogels were prepared from various pectins including pectic acid, apple-derived pectin and citrus-derived pectin by treatment with CaCl2 solution. Ability of apatite formation in SBF and mechanical properties of the gels were examined. The apatite-forming ability increased in the order (pectic acid)<(apple-derived pectin)<(citrus-derived pectin). It was suggested that the apatite-forming ability of the pectin gels is governed by not only the amount of carboxyl groups but also changes in Ca2+ concentration and pH in surrounding solutions. Young's modulus of the pectin gels was similar to natural bone, although tensile strength is a little lower.

Functionally graded bioactive glass coating on magnesia partially stabilized zirconia (Mg-PSZ) for enhanced biocompatibility

The coating of magnesia partially stabilized zirconia (Mg-PSZ) with a bioactive glass was investigated for enhancing the bioactivity and bone-bonding ability of Mg-PSZ orthopedic implants. Individual coatings of three different bioactive glasses were prepared by depositing a concentrated suspension of the glass particles on Mg-PSZ substrates, followed by sintering at temperatures between 750 degrees C and 850 degrees C. Two silicate-based glass compositions (designated 13-93 and 6P68), and a borosilicate glass composition (H12) were investigated. The microstructure and adhesive strength of the coatings were characterized, and the in vitro bioactivity of the glasses was compared by measuring their conversion kinetics to hydroxyapatite in an aqueous phosphate solution at 37 degrees C. The 6P68 glass provided the highest adhesive strength (40 +/- 2 MPa) but showed very limited bioactivity, whereas the H12 glass had lower adhesive strength (18 +/- 2 MPa) but the highest bioactivity. A functionally graded coating, consisting of a 6P68 interfacial layer and an H12 surface layer, was developed to provide a coating with high adhesive strength coupled with rapid in vitro bioactivity.

Apatite-forming ability of polyglutamic acid hydrogels in a body-simulating environment

Artificial joints can replace damaged joints provided the surrounding bone is sufficiently dense. However, elderly patients generally have reduced osteoporosis-associated bone density. Therefore, restitution of bone density is essential to ensure implantation. Injectable and resorbable bioactive fillers with bone-bonding ability (osteoconductivity) are promising, as osteoporosis can be reversed with minimal invasion. Osteoconduction occurs through the surface formation of biologically active hydroxyapatite via reactions with body fluids. Heterogeneous nucleation of the hydroxyapatite is catalysed by specific surface functional groups. In addition, release of Ca2+ ions into the surrounding fluids enhances apatite nucleation by increasing its degree of supersaturation. We tested injectable bioactive filler made from cross-linked polyglutamic acid (PGA). This has many carboxyl groups that facilitate apatite nucleation. An insoluble hydrogel can be formed by cross-linkage. We exposed PGA gels to a simulated body fluid for 7 days. Trace amounts of calcium phosphate were formed, but were not identified as bone-like apatite by X-ray diffraction. However, formation of a bone-like apatite layer was detected using pre-treatment with CaCl2 solutions (>0.01 mol dm(-3)) dose dependently. Thus, this chemically cross-linked PGA gel could induce the heterogeneous nucleation of hydroxyapatite in a body environment, and this was enhanced by pre-treatment with CaCl2.

Enhancement of bone-bonding ability of bioactive titanium by prostaglandin E2 receptor selective agonist

Systemic administration of prostaglandin E2 receptor (EP4) selective agonist increases both bone formation and resorption, and consequently leads to an increase in bone mass. Although previous studies have reported that EP4 agonist enhanced bone remodeling and fracture healing, it was not known if EP4 agonist activates the bone–biomaterial interface. Bioactive titanium prepared by chemical and thermal treatment can bond to living bone and is suitable for use in clinical applications in cementless fixation devices. Therefore, we examined whether the administration of EP4 agonist enhances the bonding strength between bone and bioactive titanium. Bioactive titanium plates were inserted into the tibia bone of rabbits and examined histologically and biomechanically at 4, 8, and 16 weeks. EP4 agonist was administrated systemically every 2 weeks after surgery. A non-administrated control group, a low-dose group (10 μg/kg body weight (BW)), and a high-dose group (100 μg/kg BW) were compared. The bonding strength of bioactive titanium in the EP4 agonist groups was significantly higher than that in the control group at both 4 and 8 weeks, and enhanced bone remodeling and direct bonding around the bioactive titanium plates was observed only in the EP4 agonist groups at 4 weeks. EP4 agonist enhanced bone formation around the bioactive titanium plate, and achieved early direct bone bonding.

Development of a Bioactive Surface on a Co-Cr-Mo Alloy during Investment Casting or Heat Treatment

Two different techniques were used to promote a bioactive surface on a cobalt base alloy: i) the cobalt alloy melt was cast into wollastonite-coated cavities of an investment mold, or ii) wollasonite-encapsulated as-cast samples were heat treated at 1220°C for 1 h, this is the typical treatment performed to this alloy for improving its mechanical behavior. In vitro bioactivity was assessed by immersing samples in a simulated body fluid for 21 days. Potentially bioactive layers were obtained in both of the cases. A thicker apatite layer was formed on the samples obtained by investment casting. However, since the heat treatment needs to be performed, the heat treatment method is also a promising technique for promoting the bone-bonding ability of this Co alloy.

Preparation of bioactive microspheres of organic modified calcium silicates through sol–gel processing

Bioactive ceramics show specific biological activity, a bone-bonding ability, and are used as bone-repairing materials. Particles of bioactive ceramics may be used as fillers for fabricating bioactive composites where bioactive fillers are dispersed in a polymer matrix. Chemical bonding between the filler and the organic matrix requires an effective organic modification of the bioactive filler. Previous studies have reported that inorganic glasses in the CaO–SiO2 system act as fundamental components showing bioactivity, as they show a high potential to form bone-like apatite after exposure to a body fluid. Therefore, organically modified microspheres composed of CaO–SiO2 gels can be useful as bioactive fillers to produce bioactive composites. In this study, the conditions for the preparation of organically modified gels composed of CaO–SiO2 were investigated using sol–gel processing of tetraethoxysilane, calcium nitrate tetrahydrate and silane coupling agents (SCAs), such as 3-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, and 3-glycidoxypropyltrimethoxysilane (GPS), along with polyethyleneglycol (PEG). Spherical particles with diameter of 2–3 μm were obtained when adding the SCAs, except for GPS with PEG. Incorporation of the SCAs was confirmed using Fourier transform infrared spectroscopy. All the samples prepared with the SCAs formed bone-like apatite on their surfaces in a simulated body fluid within a period of 1 day. These results indicate that bioactive microspheres of organically modified CaO–SiO2 gels can be obtained using sol–gel processing with SCAs.

Electrochemical galvanostatic intermittent titration technique study of biomimetic apatite formation on chemically treated titanium

Titanium metal development with bone-bonding ability has an increasing demand because of its good properties in clinical applications. Apatite formation on the surface of metal can easily form the bond contact to living bone. The apatite formation can be assessed in vitro using a simulated body fluid (SBF) that has almost equal compositions of inorganic ions to human blood plasma. Galvanostatic intermittent titration technique (GITT) is used to investigate the growth of apatite on chemically treated pure titanium pretreated in NaOH and in C 2O 4H 2 at different periods of time. Scanning electron microscopy (SEM), electron dispersive X-ray analysis (EDX) of titanium surface and solution analyses confirmed the apatite formation and its growth is dependant on time. From GITT, SEM, and calcium ion depletion in the SBF, both pretreatments of C 2O 4H 2 and NaOH were suitable methods for providing the metal implant with bone-bonding ability. However, X-ray diffraction showed that calcium phosphate could form only on the NaOH-pretreated titanium. The TiH 2 is one of the key factor responsible for the growth of apatite on titanium surface.

In vitro apatite formation on chemically treated (P/M) Ti–13Nb–13Zr

Objectives Titanium alloys are considered the material of choice when used as endosteal part of implants. However, they are not able to bond directly to bone. The objective of this study was to suggest a chemical surface treatment for Ti–13Nb–13Zr to initiate the formation of hydroxy carbonated apatite (HCA) during in vitro bioactivity tests in simulated body fluid (SBF). Methods Titanium, niobium, and zirconium hydride powders were blended, compacted and sintered. Sintered Ti–13Nb–13Zr samples were etched in HCl, H 3PO 4, and in a mixture of HF + HNO 3, respectively, and subsequently pretreated in NaOH. The influence of acid etching conditions on the microstructure of the Ti–13Nb–13Zr alloys as well as on the rate of HCA formation was evaluated using SEM-EDS, FTIR, and gravimetric analyses. Results Sintered Ti–13Nb–13Zr alloys consist of a Widmannstätten (α + β) microstructure. Exposure of chemically etched and NaOH activated samples to SBF for 1 week leads to the formation of a HCA layer on the surface of HCl as well as H 3PO 4 treated samples. No HCA formation was found on HNO 3 treated samples. After 2 weeks in SBF the mass increase, that can be correlated to the HCA formation rate, was the highest for HCl pretreated samples (2.4 mg/cm 2) followed by H 3PO 4 (0.8 mg/cm 2) and HNO 3 pretreated ones (0.2 mg/cm 2). Significance Since the in vitro HCA formation from SBF is generally accepted as a typical feature for bioactive materials, it is supposed that HCl etching with subsequent NaOH treatment might enhance the in vivo bone-bonding ability of Ti–13Nb–13Zr.

Cytotoxicity of zinc-containing bioactive glasses in contact with human osteoblasts

Bioactive glasses such as Hench's 45S5 have applications to tissue engineering and bone repair: the insertion of zinc has been proposed to improve their bone-bonding ability and to slacken their dissolution in extracellular body fluids. In view of a potential clinical application, we have investigated whether zinc-containing 45S5 (HZ) glasses might be cytotoxic for human MG-63 osteoblasts. In our experimental conditions, after 24 h of incubation HZ glasses released significant amounts of Zn 2+ and induced in MG-63 cells release of lactate dehydrogenase (index of cytotoxicity) and the following indexes of oxidative stress: (i) accumulation of intracellular malonyldialdehyde, (ii) increased activity of pentose phosphate pathway, (iii) increased expression of heme oxygenase-1, (iv) increased activity of Cu,Zn-superoxide dismutase, (v) decreased level of intracellular thiols. These effects were inversely related to the zinc content of glass powders, were mimicked by ZnCl 2 solutions and were prevented by either metal chelators (EDTA, NTA) or the antioxidant ascorbate, suggesting that Zn 2+ released fastly from HZ glasses can cause MG-63 cell damage via an oxidative stress. This work highlights the importance of designing Zn-containing bioactive glasses without cytotoxic effects and gives supplementary information about the prooxidant role of zinc in living systems.

Acceleration of apatite nucleation on microrough bioactive titanium for bone‐replacing implants

The viability of a new two-step method for obtaining bioactive microrough titanium surfaces for bone replacing implants has been evaluated. The method consists of (1) Grit blasting on titanium surface to roughen it; and (2) Thermo-chemical treating to obtain a bioactive surface with bone-bonding ability by means of nucleating and growing an apatite layer on the treated surface of the metal. The aim of this work is to evaluate the effect of surface roughness and chemical composition of the grit-blasting particles on the ability of the surfaces of nucleating and growing a homogeneous apatite layer. The determination and kinetics of the nucleation and growing of the apatite layer on the surfaces has mainly been studied with environmental scanning electron microscopy (ESEM) and grazing-incidence X-ray diffractometry. The results show that Al(2)O(3)-blasted and thermochemically-treated titanium surfaces accelerates nucleation of the apatite, whereas SiC-blasted and thermochemically-treated titanium surfaces inhibits apatite nucleation, compared with the well studied polished and thermochemically-treated titanium surfaces. The acceleration of the apatite nucleation on the Al(2)O(3)-blasted microrough titanium surfaces is because concave parts of the microroughness that are obtained during grit blasting provides to the rough and bioactive surfaces with a chemical- and electrostatic-favored situation for apatite nucleation. This consists of a high density of surface negative charges (also assisted by the nanoroughness of the surface obtained after the thermochemical treatment) and an increased concentration of the Ca(2+)-ions of the fluid, which have a limited mobility at the bottom of the concave parts.