Strontium substitution of gelatin modified calcium hydrogen phosphates as porous hard tissue substitutes.

Aiming at the generation of a high strontium-containing degradable bone substitute, the exchange of calcium with strontium in gelatin-modified brushite was investigated. The ion substitution showed two mineral groups, the high-calcium containing minerals with a maximum measured molar Ca/Sr ratio of 80%/20% (mass ratio 63%/37%) and the high-strontium containing ones with a maximum measured molar Ca/Sr ratio of 21%/79% (mass ratio 10%/90%). In contrast to the high-strontium mineral phases, a high mass loss was observed for the calcium-based minerals during incubation in cell culture medium (alpha-MEM), but also an increase in strength owing to dissolution and re-precipitation. This resulted for the former in a decrease of cation concentration (Ca + Sr) in the medium, while the pH value decreased and the phosphate ion concentration rose significantly. The latter group of materials, the high-strontium containing ones, showed only a moderate change in mass and a decrease in strength, but the Ca + Sr concentration remained permanently above the initial calcium concentration in the medium. This might be advantageous for a future planned application by supporting bone regeneration on the cellular level.

UV-Pre-Treated and Protein-Adsorbed Titanium Implants Exhibit Enhanced Osteoconductivity.

Titanium materials are essential treatment modalities in the medical field and serve as a tissue engineering scaffold and coating material for medical devices. Thus, there is a significant demand to improve the bioactivity of titanium for therapeutic and experimental purposes. We showed that ultraviolet light (UV)-pre-treatment changed the protein-adsorption ability and subsequent osteoconductivity of titanium. Fibronectin (FN) adsorption on UV-treated titanium was 20% and 30% greater after 1-min and 1-h incubation, respectively, than that of control titanium. After 3-h incubation, FN adsorption on UV-treated titanium remained 30% higher than that on the control. Osteoblasts were cultured on titanium disks after 1-h FN adsorption with or without UV-pre-treatment and on titanium disks without FN adsorption. The number of attached osteoblasts during the early stage of culture was 80% greater on UV-treated and FN-adsorbed (UV/FN) titanium than on FN-adsorbed (FN) titanium; osteoblasts attachment on UV/FN titanium was 2.6- and 2.1-fold greater than that on control- and UV-treated titanium, respectively. The alkaline phosphatase activity of osteoblasts on UV/FN titanium was increased 1.8-, 1.8-, and 2.4-fold compared with that on FN-adsorbed, UV-treated, and control titanium, respectively. The UV/FN implants exhibited 25% and 150% greater in vivo biomechanical strength of bone integration than the FN- and control implants, respectively. Bone morphogenetic protein-2 (BMP-2) adsorption on UV-treated titanium was 4.5-fold greater than that on control titanium after 1-min incubation, resulting in a 4-fold increase in osteoblast attachment. Thus, UV-pre-treatment of titanium accelerated its protein adsorptivity and osteoconductivity, providing a novel strategy for enhancing its bioactivity.

Bioglass/PLGA associated to photobiomodulation: effects on the healing process in an experimental model of calvarial bone defect.

Bioactive glasses (BG) are known for their ability to bond to bone tissue. However, in critical situations, even the osteogenic properties of BG may be not enough to induce bone consolidation. Thus, the enrichment of BG with polymers such as Poly (D, L-lactic-co-glycolic) acid (PLGA) and associated to photobiomodulation (PBM) may be a promising strategy to promote bone tissue healing. The aim of the present study was to investigate the in vivo performance of PLGA supplemented BG, associated to PBM therapy, using an experimental model of cranial bone defect in rats. Rats were distributed in 4 different groups (Bioglass, Bioglass/PBM, Bioglas/PLGA and BG/PLGA/PBM). After the surgical procedure to induce cranial bone defects, the pre-set samples were implanted and PBM treatment (low-level laser therapy) started (808 nm, 100 mW, 30 J/cm2). After 2 and 6 weeks, animals were euthanized, and the samples were retrieved for the histopathological, histomorphometric, picrosirius red staining and immunohistochemistry analysis. At 2 weeks post-surgery, it was observed granulation tissue and areas of newly formed bone in all experimental groups. At 6 weeks post-surgery, BG/PLGA (with or without PBM) more mature tissue around the biomaterial particles. Furthermore, there was a higher deposition of collagen for BG/PLGA in comparison with BG/PLGA/PBM, at second time-point. Histomorphometric analysis demonstrated higher values of BM.V/TV for BG compared to BG/PLGA (2 weeks post-surgery) and N.Ob/T.Ar for BG/PLGA compared to BG and BG/PBM (6 weeks post-surgery). This current study concluded that the use of BG/PLGA composites, associated or not to PBM, is a promising strategy for bone tissue engineering.

The effect of acoustic radiation force on osteoblasts in cell/hydrogel constructs for bone repair.

Ultrasound, or the application of acoustic energy, is a minimally invasive technique that has been used in diagnostic, surgical, imaging, and therapeutic applications. Low-intensity pulsed ultrasound (LIPUS) has been used to accelerate bone fracture repair and to heal non-union defects. While shown to be effective the precise mechanism behind its utility is still poorly understood. In this study, we considered the possibility that LIPUS may be providing a physical stimulus to cells within bony defects. We have also evaluated ultrasound as a means of producing a transdermal physical force that could stimulate osteoblasts that had been encapsulated within collagen hydrogels and delivered to bony defects. Here we show that ultrasound does indeed produce a measurable physical force and when applied to hydrogels causes their deformation, more so as ultrasound intensity was increased or hydrogel stiffness decreased. MC3T3 mouse osteoblast cells were then encapsulated within hydrogels to measure the response to this force. Statistically significant elevated gene expression for alkaline phosphatase and osteocalcin, both well-established markers of osteoblast differentiation, was noted in encapsulated osteoblasts (p < 0.05), suggesting that the physical force provided by ultrasound may induce bone formation in part through physically stimulating cells. We have also shown that this osteoblastic response is dependent in part on the stiffness of the encapsulating hydrogel, as stiffer hydrogels resulted in reducing or reversing this response. Taken together this approach, encapsulating cells for implantation into a bony defect that can potentially be transdermally loaded using ultrasound presents a novel regenerative engineering approach to enhanced fracture repair.

On the interactions of human bone cells with Ti6Al4V thermally oxidized by means of laser shock processing.

We investigated a Ti6Al4V alloy modified by means of laser peening in the absence of sacrificial coatings. As a consequence of the temperature rise during laser focusing, melting and ablation generated an undulated surface that exhibits an important increase in the content of titanium oxides and OH- ions. Human mesenchymal stem cells and osteoblasts cultured on the oxidized alloy develop noticeable filopodia and lamellipodia. Their paxillin-stained focal adhesions are smaller than in cells attached to the untreated alloy and exhibit a marked loss of colocalization with the ends of actin stress fibers. An important imbalance of phosphorylation and/or dephosphorylation of the focal adhesion kinase is detected in cells grown on the oxidized alloy. Although these mechanisms of adhesion are deeply altered, the surface treatment does not affect cell attachment or proliferation rates on the alloy. Human mesenchymal stem cells cultured on the treated alloy in media containing osteogenic inducers differentiate towards the osteoblastic phenotype to a higher extent than those on the untreated surface. Also, the specific functions of human osteoblasts cultured on these media are enhanced on the treated alloy. In summary, laser peening tailors the Ti6Al4V surface to yield an oxidized layer with increased roughness that allows the colonization and activities of bone-lineage cells.

Enhancement of bioactivity on medical polymer surface using high power impulse magnetron sputtered titanium dioxide film.

This study utilizes a novel technique, high power impulse magnetron sputtering (HIPIMS), which provides a higher ionization rate and ion bombardment energy than direct current magnetron sputtering (DCMS), to deposit high osteoblast compatible titanium dioxide (TiO2) coatings with anatase (A-TiO2) and rutile (R-TiO2) phases onto the biomedical polyetheretherketone (PEEK) polymer substrates at low temperature. The adhesions of TiO2 coatings that were fabricated using HIPIMS and DCMS were compared. The in vitro biocompatibility of these coatings was confirmed. The results reveal that HIPIMS can be used to prepare crystallinic columnar A-TiO2 and R-TiO2 coatings on PEEK substrate if the ratio of oxygen to argon is properly controlled. According to a tape adhesion test, the HIPIMS-TiO2 coatings had an adhesion grade of 5B even after they were immersed in simulated body fluid (SBF) environments for 28days. Scratch tests proved that HIPIMS-TiO2 coatings undergo cohesive failure. These results demonstrate that the adhesive force between HIPIMS-TiO2 coating/PEEK is stronger than that between DCMS-TiO2 coating/PEEK. After a long period (28days) of immersion in SBF, a bone-like crystallinic hydroxyapatite layer with a corresponding Ca/P stoichiometry was formed on both HIPIMS-TiO2. The osteoblast compatibility of HIPIMS-TiO2 exceeded that of the bare PEEK substrate. It is also noticeable that the R-TiO2 performed better in vitro than the A-TiO2 due to the formation of many negatively charged hydroxyl groups (-OH(-)) groups on R-TiO2 (110) surface. In summary, the HIPIMS-TiO2 coatings satisfied the requirements for osseointegration, suggesting the possibility of using HIPIMS to modify the PEEK surface with TiO2 for spinal implants.

Preparation and characterization of laser cladding wollastonite derived bioceramic coating on titanium alloy.

The bioceramic coating is fabricated on titanium alloy (Ti6Al4V) by laser cladding the preplaced wollastonite (CaSiO3) powders. The coating on Ti6Al4V is characterized by x-ray diffraction, scanning electron microscopy coupled with energy dispersive spectroscopy, and attenuated total reflection Fourier-transform infrared. The interface bonding strength is measured using the stretching method using an RGD-5-type electronic tensile machine. The microhardness distribution of the cross-section is determined using an indentation test. The in vitro bioactivity of the coating on Ti6Al4V is evaluated using the in vitro simulated body fluid (SBF) immersion test. The microstructure of the laser cladding sample is affected by the process parameters. The coating surface is coarse, accidented, and microporous. The cross-section microstructure of the ceramic layer from the bottom to the top gradually changes from cellular crystal, fine cellular-dendrite structure to underdeveloped dendrite crystal. The coating on Ti6Al4V is composed of CaTiO3, CaO, α-Ca2SiO4, SiO2, and TiO2. After soaking in the SBF solution, the calcium phosphate layer is formed on the coating surface.

Comparative study of membranes induced by PMMA or silicone in rats, and influence of external radiotherapy.

The induced membrane technique has been used for long bone defect reconstruction after traumatism. One of the major drawbacks of this method is the difficult removal of the polymethyl methacrylate spacer after membrane formation. We therefore replaced the stiff PMMA spacer with a semi-flexible medical grade silicone spacer. This study aimed to compare subcutaneously formed membranes, induced by PMMA and silicone, in the irradiated or not irradiated areas within 28 rats that received the spacers. Histological analysis was performed to evaluate the composition of the membrane and to quantify the amount of vessels. Histomorphometric measurements were used to evaluate membranes' thickness, while fibrosis and inflammation were scored. The expression of VEGF and BMP-2 in lysates of the crushed membranes was determined by Western blotting. ALP expression was analyzed in HBMSC cultures in contact with the same lysates. Non-irradiated membranes induced by the two spacer types were non-inflammatory, fibrous and organized in layers. Irradiation did not change the macroscopic properties of membranes that were induced by silicone, while PMMA induced membranes were sensitive to the radiotherapy, resulting in thicker, strongly inflammatory membranes. Irradiated membranes showed an overall reduced osteogenic potential. Medical grade silicone is safe for the use in radiotherapy and might therefore be of great advantage for patients in need of cancer treatment.

Thermal effect on thermoluminescence response of hydroxyapatite.

This paper presents the experimental results of the thermoluminescence (TL) induced by gamma radiation in synthetic hydroxyapatite (HAp) obtained by the precipitation method, using Ca(NO3)2·4H2O and (NH4)2HPO4 and calcined at different temperatures. The structural and morphological characterization was carried out by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. TL response as a function of gamma radiation dose was in a wide range, where intensity was enhanced in the sample annealed at 900°C, which tricalcium diphosphate (TCP) phase appear. Fading of the TL was also studied.

Avaliação de diferentes protocolos de aplicação do laser de baixa intensidade associado ou não ao osso bovino inorgânico (Bio-Oss®) na cicatrização de defeitos ósseos criados cirurgicamente em calvárias de ratos: estudo histológico e histométrico / Evaluation of different protocols of low-level laser (LLL) application combined or not with inorganic bovine bone (Bio-Oss®) in the healing of surgically created bone defects in rat calvaria: histological and histometric study

O propósito deste estudo foi avaliar diferentes protocolos de aplicação do laser de baixa intensidade (LBI) associados ou não ao osso bovino inorgânico (Bio-Oss®) na cicatrização de defeitos ósseos de tamanho crítico (DTC) em calvárias de ratos. Foram utilizados 90 ratos machos adultos (Rattus norvegicus, albinus, Wistar). Um defeito de tamanho crítico (DTC) de 5 mm de diâmetro foi criado cirurgicamente na calvária de cada animal. Os animais foram divididos igualmente (n=10) e aleatoriamente em 9 gruposexperimentais: 1) grupo C (controle), 2) grupo LBI (4J) (laser de baixa intensidade GaAlAs, 730 nm, 100 mW, 4J, 140 J/cm2), 3) Grupo LBI (6J) (laser de baixa intensidade GaAlAs, 730 nm, 100 mW, 6J, 210 J/cm2), 4) Grupo BO (osso bovino inorgânico), 5) Grupo BO + LBI (4J) (osso bovino inorgânico + laser de baixa intensidade 4J), 6) Grupo BO + LBI (6J) (osso bovino inorgânico + laser de baixa intensidade 6J), 7) Grupo OA (osso autógeno), 8) Grupo OA + LBI (4J) (osso autógeno + laser de baixa intensidade 4J), 9) Grupo OA + LBI (6J) (osso autógeno + laser de baixa intensidade 6J). Os animais foram submetidos à eutanásia aos 30 dias pós-operatórios. Foram avaliadas a área de osso neoformado (AON), extensão linear de osso (ELO) e área de partículas remanescentes (APR). Os dados foram submetidos ao teste paramétrico ANOVA, seguido pelo teste de Tukey (p<0,05). O grupo BO+LBI (6J) demonstrou maior média (48,57 ± 28,22%) de AON e o grupo C a menor média (9,96 ± 4,49%) de AON. Os grupos LBI (6J), OA+LBI (6J) e BO+LBI (6J) demonstraram diferenças estatisticamente significativas de AON em relação ao grupo C. Em relação a ELO, apenas os grupos BO e BO+LBI (4J) não demonstraram diferenças estatisticamente significativas quando comparados ao grupo C, e a maior diferença entre as médias de ELO foram nas comparações do grupo LBI (6J) (76,55 ± 15,54%) com o grupo C (16,00 ± 9,86%. Maior APR foi observada nos grupos em que BO não foi irradiado pelo LBI. Porém, quando...

The purpose of this study was to evaluate different protocols of low-level laser (LLL) application combined or not with inorganic bovine bone (Bio-Oss®) in the healing process of bone defects of critical size (CSD) in rat calvaria. 90 male adult rats (Rattusnorvegicus, albinus, Wistar) were used. A critical size defect (CSD) of 5 mm in diameter was surgically created in the calvaria of each rat. The rats were then divided equally (n=10) and randomly into 9 experimental groups: 1) Group C (control) 2) Group LBI (4J) (low-level laser - GaAlAs, 730 nm, 100 mW, 4J, 140 J/cm2), 3) Group LBI (6) (low- level laser - GaAlAs, 730 nm, 100 mW, 6J, 210 J/cm2), 4) Group BO (inorganic bovine bone), 5) Group BO + LBI (4J) (inorganic bovine bone + low-level laser 4J), 6) Group BO LBI (6J) (inorganic bovine bone + low-level laser 6J), 7) Group OA (autogenous bone), 8) Group OA + LBI (4J) (autogenous bone + low-level laser 4J), 9 Group OA + LBI (6J) (autogenous bone + low-level laser 6J). The rats utilized were euthanized 30 days post-operation. The areas of new bone formation (ANB), linear extension bone (LEB), and areas of remaining particles (ARP) were evaluated. The data underwent the parametric ANOVA test, followed by the Tukey test (p<0,05). Group BO+LBI (6J) presented the greatest average (48,57 ± 28,22%) of ANB and Group C presented the lowest average (9,96 ± 4,49%) of ANB. The groups LBI (6J), OA+LBI (6J), and BO+LBI (6J) presented statistically significant differences of ANB in comparison to Group C. Regarding the LEB, only the groups BO and BO+LBI (4J) did not present differences statistically significant in comparison to Group C. The largest difference between the averages of LEB were in the comparison of Group LBI (6J) (76,55 ± 15,54%) with Group C (16,00 ± 9,86%). The largest ARP was observed in the groups where the inorganic bovine bone was not irradiated by the LLL. However, when comparing Group BO+LBI (6J) to Group OA+LBI (4J) and...

Avaliação de diferentes protocolos de aplicação do laser de baixa intensidade associado ou não ao osso bovino inorgânico (Bio-Oss®) na cicatrização de defeitos ósseos criados cirurgicamente em calvárias de ratos: estudo histológico e histométrico / Evaluation of different protocols of low-level laser (LLL) application combined or not with inorganic bovine bone (Bio-Oss®) in the healing of surgically created bone defects in rat calvaria: histological and histometric study

O propósito deste estudo foi avaliar diferentes protocolos de aplicação do laser de baixa intensidade (LBI) associados ou não ao osso bovino inorgânico (Bio-Oss®) na cicatrização de defeitos ósseos de tamanho crítico (DTC) em calvárias de ratos. Foram utilizados 90 ratos machos adultos (Rattus norvegicus, albinus, Wistar). Um defeito de tamanho crítico (DTC) de 5 mm de diâmetro foi criado cirurgicamente na calvária de cada animal. Os animais foram divididos igualmente (n=10) e aleatoriamente em 9 gruposexperimentais: 1) grupo C (controle), 2) grupo LBI (4J) (laser de baixa intensidade GaAlAs, 730 nm, 100 mW, 4J, 140 J/cm2), 3) Grupo LBI (6J) (laser de baixa intensidade GaAlAs, 730 nm, 100 mW, 6J, 210 J/cm2), 4) Grupo BO (osso bovino inorgânico), 5) Grupo BO + LBI (4J) (osso bovino inorgânico + laser de baixa intensidade 4J), 6) Grupo BO + LBI (6J) (osso bovino inorgânico + laser de baixa intensidade 6J), 7) Grupo OA (osso autógeno), 8) Grupo OA + LBI (4J) (osso autógeno + laser de baixa intensidade 4J), 9) Grupo OA + LBI (6J) (osso autógeno + laser de baixa intensidade 6J). Os animais foram submetidos à eutanásia aos 30 dias pós-operatórios. Foram avaliadas a área de osso neoformado (AON), extensão linear de osso (ELO) e área de partículas remanescentes (APR). Os dados foram submetidos ao teste paramétrico ANOVA, seguido pelo teste de Tukey (p<0,05). O grupo BO+LBI (6J) demonstrou maior média (48,57 ± 28,22%) de AON e o grupo C a menor média (9,96 ± 4,49%) de AON. Os grupos LBI (6J), OA+LBI (6J) e BO+LBI (6J) demonstraram diferenças estatisticamente significativas de AON em relação ao grupo C. Em relação a ELO, apenas os grupos BO e BO+LBI (4J) não demonstraram diferenças estatisticamente significativas quando comparados ao grupo C, e a maior diferença entre as médias de ELO foram nas comparações do grupo LBI (6J) (76,55 ± 15,54%) com o grupo C (16,00 ± 9,86%. Maior APR foi observada nos grupos em que BO não foi irradiado pelo LBI. Porém, quando...

The purpose of this study was to evaluate different protocols of low-level laser (LLL) application combined or not with inorganic bovine bone (Bio-Oss®) in the healing process of bone defects of critical size (CSD) in rat calvaria. 90 male adult rats (Rattusnorvegicus, albinus, Wistar) were used. A critical size defect (CSD) of 5 mm in diameter was surgically created in the calvaria of each rat. The rats were then divided equally (n=10) and randomly into 9 experimental groups: 1) Group C (control) 2) Group LBI (4J) (low-level laser - GaAlAs, 730 nm, 100 mW, 4J, 140 J/cm2), 3) Group LBI (6) (low- level laser - GaAlAs, 730 nm, 100 mW, 6J, 210 J/cm2), 4) Group BO (inorganic bovine bone), 5) Group BO + LBI (4J) (inorganic bovine bone + low-level laser 4J), 6) Group BO LBI (6J) (inorganic bovine bone + low-level laser 6J), 7) Group OA (autogenous bone), 8) Group OA + LBI (4J) (autogenous bone + low-level laser 4J), 9 Group OA + LBI (6J) (autogenous bone + low-level laser 6J). The rats utilized were euthanized 30 days post-operation. The areas of new bone formation (ANB), linear extension bone (LEB), and areas of remaining particles (ARP) were evaluated. The data underwent the parametric ANOVA test, followed by the Tukey test (p<0,05). Group BO+LBI (6J) presented the greatest average (48,57 ± 28,22%) of ANB and Group C presented the lowest average (9,96 ± 4,49%) of ANB. The groups LBI (6J), OA+LBI (6J), and BO+LBI (6J) presented statistically significant differences of ANB in comparison to Group C. Regarding the LEB, only the groups BO and BO+LBI (4J) did not present differences statistically significant in comparison to Group C. The largest difference between the averages of LEB were in the comparison of Group LBI (6J) (76,55 ± 15,54%) with Group C (16,00 ± 9,86%). The largest ARP was observed in the groups where the inorganic bovine bone was not irradiated by the LLL. However, when comparing Group BO+LBI (6J) to Group OA+LBI (4J) and...

Energy deposition of H and He ion beams in hydroxyapatite films: a study with implications for ion-beam cancer therapy.

Ion-beam cancer therapy is a promising technique to treat deep-seated tumors; however, for an accurate treatment planning, the energy deposition by the ions must be well known both in soft and hard human tissues. Although the energy loss of ions in water and other organic and biological materials is fairly well known, scarce information is available for the hard tissues (i.e., bone), for which the current stopping power information relies on the application of simple additivity rules to atomic data. Especially, more knowledge is needed for the main constituent of human bone, calcium hydroxyapatite (HAp), which constitutes 58% of its mass composition. In this work the energy loss of H and He ion beams in HAp films has been obtained experimentally. The experiments have been performed using the Rutherford backscattering technique in an energy range of 450-2000 keV for H and 400-5000 keV for He ions. These measurements are used as a benchmark for theoretical calculations (stopping power and mean excitation energy) based on the dielectric formalism together with the MELF-GOS (Mermin energy loss function-generalized oscillator strength) method to describe the electronic excitation spectrum of HAp. The stopping power calculations are in good agreement with the experiments. Even though these experimental data are obtained for low projectile energies compared with the ones used in hadron therapy, they validate the mean excitation energy obtained theoretically, which is the fundamental quantity to accurately assess energy deposition and depth-dose curves of ion beams at clinically relevant high energies. The effect of the mean excitation energy choice on the depth-dose profile is discussed on the basis of detailed simulations. Finally, implications of the present work on the energy loss of charged particles in human cortical bone are remarked.

The effect of magnetic field on electrochemically deposited calcium phosphate/collagen coatings.

Nanostructured calcium phosphate/collagen (CaP/COL) coatings were deposited on the carbon/carbon (C/C) composites through electrochemical deposition (ECD) under magnetic field. The effect of magnetic fields with different orientations on the morphology and composition was investigated. Both the morphology and composition of the coatings could be altered by superimposed magnetic field. Under zero magnetic field and magnetic field, three-dimensional network structure consisting of collagen fibers and CaP were formed on the C/C substrate. The applied magnetic field in the electric field helped to form nanostructured and plate-like CaP on collagen fibers. For the ECD under magnetic field, the Ca/P molar ratio of the coatings was lower than the one under B=0. This may be contributed to the decreased electrical resistance or the increased electrical conductivity of electrolyte solutions under magnetic field. The nanosized CaP/COL coatings exhibited the similar morphology to the human bone and could present excellent cell bioactivity and osteoblast functions.

Thermal, creep-recovery and viscoelastic behavior of high density polyethylene/hydroxyapatite nano particles for bone substitutes: effects of gamma radiation.

BACKGROUND: High Density Polyethylene (HDPE) is one of the most often used polymers in biomedical applications. The limitations of HDPE are its visco-elastic behavior, low modulus and poor bioactivity. To improve HDPE properties, HA nanoparticles can be added to form polymer composite that can be used as alternatives to metals for bone substitutes and orthopaedic implant applications. METHOD: In our previous work (BioMedical Engineering OnLine 2013), different ratios of HDPE/HA nanocomposites were prepared using melt blending in a co-rotating intermeshing twin screw extruder. The accelerated aging effects on the tensile properties and torsional viscoelastic behavior (storage modulus (G') and Loss modulus (G")) at 80°C of irradiated and non-irradiated HDPE/HA was investigated. Also the thermal behavior of HDPE/HA were studied. In this study, the effects of gamma irradiation on the tensile viscoelastic behavior (storage modulus (E') and Loss modulus (E")) at 25°C examined for HDPE/HA nanocomposites at different frequencies using Dynamic Mechanical Analysis (DMA). The DMA was also used to analyze creep-recovery and relaxation properties of the nanocomposites. To analyze the thermal behavior of the HDPE/HA nanocomposite, Differential Scanning Calorimetry (DSC) was used. RESULTS: The microscopic examination of the cryogenically fractured surface revealed a reasonable distribution of HA nanoparticles in the HDPE matrix. The DMA showed that the tensile storage and loss modulus increases with increasing the HA nanoparticles ratio and the test frequency. The creep-recovery behavior improves with increasing the HA nanoparticle content. Finally, the results indicated that the crystallinity, viscoelastic, creep recovery and relaxation behavior of HDPE nanocomposite improved due to gamma irradiation. CONCLUSION: Based on the experimental results, it is found that prepared HDPE nanocomposite properties improved due to the addition of HA nanoparticles and irradiation. So, the prepared HDPE/HA nanocomposite appears to have fairly good comprehensive properties that make it a good candidate as bone substitute.

Poly(ether-ether-ketone) orthopedic bearing surface modified by self-initiated surface grafting of poly(2-methacryloyloxyethyl phosphorylcholine).

We investigated the production of free radicals on a poly(ether-ether-ketone) (PEEK) substrate under ultraviolet (UV) irradiation. The amount of the ketyl radicals produced from the benzophenone (BP) units in the PEEK molecular structure initially increased rapidly and then became almost constant. Our observations revealed that the BP units in PEEK acted as photoinitiators, and that it was possible to use them to control the graft polymerization of poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC). This "self-initiated surface graft polymerization" method is very convenient in the absence of external photoinitiator. We also investigated the effects of the monomer concentration and UV irradiation time on the extent of the grafted PMPC layer. Furthermore, as an application to improving the durability of artificial hips, we demonstrated the nanometer-scale photoinduced grafting of PMPC onto PEEK and carbon fiber-reinforced PEEK (CFR-PEEK) orthopedic bearing surfaces and interfaces. A variety of test revealed significant improvements in the water wettability, frictional properties, and wear resistance of the surfaces and interfaces.

Carbon-centered radicals in γ-irradiated bone substituting biomaterials based on hydroxyapatite.

Gamma irradiated synthetic hydroxyapatite, bone substituting materials NanoBone(®) and HA Biocer were examined using EPR spectroscopy and compared with powdered human compact bone. In every case, radiation-induced carbon centered radicals were recorded, but their molecular structures and concentrations differed. In compact bone and synthetic hydroxyapatite the main signal assigned to the CO(2) (-) anion radical was stable, whereas the signal due to the CO(3) (3-) radical dominated in NanoBone(®) and HA Biocer just after irradiation. However, after a few days of storage of these samples, also a CO(2) (-) signal was recorded. The EPR study of irradiated compact bone and the synthetic graft materials suggest that their microscopic structures are different. In FT-IR spectra of NanoBone(®), HA Biocer and synthetic hydroxyapatite the HPO(4) (2-) and CO(3) (2-) in B-site groups are detected, whereas in compact bone signals due to collagen dominate.

Biological response of laser macrostructured and oxidized titanium alloy: an in vitro and in vivo study.

PURPOSE: To assess both the in vitro and in vivo biological response of a laser modified surface in an integrated manner. A combined innovative approach applies lasers to macrostructure as well as to oxidize the surface of titanium alloy implants. MATERIALS AND METHODS: A Nd:YAG marking and ArF excimer lasers were used for macrostructuring and UV-oxidizing the surface of Ti6Al4V discs, respectively. Human fetal osteoblastic cell culture and a sheep tibia model were used to assess the cell response and the osseogeneration capability of as-machined, laser macrostructured and laser macrostructured and oxidized surfaces. RESULTS: In vitro: Laser macrostructuration alone did not promote cell response. Cellular proliferation was enhanced by the additional UV laser oxidation. In vivo: A greater significant percentage of bone-implant contact was obtained for both laser treated surfaces compared to machine-turned control samples, three months after implantation, in spite of the low cellular response for macrostructured samples. The use of sheep model for six months appears to be less adequate for a comparison because of the high level of bone integration in all samples. In spite of the often reported positive effect of titanium oxidation on the triggering of faster osseointegration, in this experiment the additional UV laser oxidation did not lead to a significant in vivo improvement. CONCLUSIONS: Laser macrostructuration of titanium alloy surfaces appears to promote bone apposition and may therefore constitute a promising surface modification strategy. In animal models, the natural process of titanium surface oxidation, because of physiologic fluids, alters properties observed in vitro with cells.

The use of light/chemically hardened polymethylmethacrylate, polyhydroxyethylmethacrylate, and calcium hydroxide graft material in combination with polyanhydride around implants in minipigs: part I: immediate stability and function.

BACKGROUND: The present study is designed as a proof-of-concept study to evaluate light/chemical hardening technology and a newly formulated polymethylmethacrylate, polyhydroxyethylmethacrylate, and calcium hydroxide (PPCH) plus polyanhydride (PA) (PPCH-PA) composite graft material as a bone substitute compared to positive and negative controls in a minipig model. METHODS: PPCH-PA (composite graft); PPCH alone (positive control), PA alone (positive control), and no graft (negative control) were compared. Four mandibular premolar teeth per quadrant were extracted; a total of 48 implants were placed into sockets in three minipigs. Abutments were placed protruding into the oral cavity 4 mm in height for immediate loading. Crestal areas and intrabony spaces were filled with PPCH-PA, PPCH, or PA using a three-phase delivery system in which all graft materials were hardened by a light cure. In the negative control group, implant sites were left untreated. At 12 weeks, block sections containing implants were obtained. Evaluations included periodontal probing, pullout-force load, and stability measurements to determine implant stability, radiographs to examine bone levels, and scanning electron microscopy (SEM)-energy-dispersed spectroscopy to determine bone-to-implant contact. RESULTS: Probing measurements did not reveal any pathologic pocket formation or bone loss. Radiographs revealed that immediate implant placement and loading resulted in bone at or slightly apical to the first thread of the implant in all groups at 12 weeks. Stability test values showed a relative clinical stability for all implants (range: -7 to +1); however, implants augmented with PPCH-PA exhibited a statistically significantly greater stability compared to all other groups (P <0.05). The newly formed bone in PPCH-PA-treated sites was well organized with less marrow spaces and well-distributed osteocytes. SEM revealed a tighter implant-socket interface in the PPCH-PA group compared to other groups with reduced microfissures and implant-bone interface fractures during pullout testing, whereas implants treated with PA or no graft showed ≈ 10-µm microfissures between the implant and bone with fractures of the intrathread bone. CONCLUSIONS: The newly formulated chemically hardened graft material PPCH-PA was useful in immediate implant placement after tooth extraction and resulted in greater stability and a well-organized implant-bone interface with immediate loading, especially in those areas where cancellous bone was present. The results of this proof-of-concept study warranted further research investigating different healing times and longer durations.

Nano-beta-tricalcium phosphates synthesis and biodegradation: 2. Biodegradation and apatite layer formation on nabo-ß-TCP synthesized via microwave treatment.

The degradation and/or apatite layer precipitation ability of porous ß-tricalcium phosphate(ß-TCP) samples treated and untreated with microwave radiation during synthesis is investigated. Microwave heating was used to accelerate the formation of CDHA with the Ca/P ratio 1.5 in a shorter processing time which later forms ß-TCP at around 650 ◦C. Soaking in simulated body fluid (SBF) for several periods (4, 8, 12, 24, 36, 48, 60 and 72 h) is performed in a cumulative manner. The deposition of an apatite layer is followed through diffuse reflected FT-IR, SEM and EDS. A microwave-treated sample having a smaller particle size than its parent induces the formation of a homogeneous carbonated apatite layer on its surface.On the other hand, the parent ß-TCP sample exhibited less ability to induce Ca­P formation after being soaked in SBF. The formation of an apatite layer is attributed to the increase in surface area consequent to reduced particle and grain sizes besides the presence of a minor amount of hydroxyapatite phase in the microwave-treated ß-TCP sample. The results prove that it is possible to control the biodegradation and apatite layer formation on sintered ß-TCP porous disks through controlling the particle size.

Microwave irradiation enhances kinetics of the biomimetic process of hydroxyapatite nanocomposites.

In situ synthesized hydroxyapatite-poly(vinyl) alcohol nanocomposite was subjected to microwave irradiation, post synthesis. Interestingly, the aging time of 1 week required for the normal biomimetic process was reduced to 1 h post microwave irradiation, as characterized by x-ray powder diffraction and transmission electron microscopy. The surface topography shows the tendency of tubules to cross-link with the help of microwave energy. The microwave energy seems to provide a directional pull to the polymer chains which could have led to an enhancement of the kinetics of phase formation.