Key Engineering Materials Vol. 631

Abstract: Amorphous calcium phosphate (ACP) is known as one of the precursors of bone hydroxyapatite (HAp). The ACP transforms into low crystalline HAp around 40°C. Zinc (Zn) is an essential trace element for the human body and has an important role in bone formation. Osteoporosis has been linked to Zn deficiency. Biomaterials that release Zn at site of bone resorption can potentially inhibit the progression of osteoporosis. In this study, we successfully prepared Zn-releasing injectable materials that consisting of ACP and alginate gel. We investigated the Zn dissolution behavior from these composite samples in environment that imitate bone metabolism. The Zn containing gel released Zn into an acetic acid buffer, which mimics the environment of osteoclast activity. In contrast, the gel sample did not released Zn when soaked in a simulated body fluid (Kokubo’s solution), a solution that mimics the environment of osteoblast activity and cell quiescence. Therefore, the ACP/alginate gel composite that is cross-linked with Zn²⁺ could control the rate of release in Zn. These gels are expected to be a Zn controlled-release intelligent material.

Abstract: The development of suitable strategies to treat ageing-related pathologies has attracted the interest of researchers in view of the increasing life expectancy in the next decades. Osteoporosis is a worldwide disease with high prevalence in humans older than 50 that dramatically increases the risk of bone fractures with associated disabilities. The innovative use of new biomaterials as models of the healthy and osteoporotic bone matrix would be a new strategy to study the physiological conditions associated with osteoporosis and the connection between microenvironment changes and the bone ageing process. In this work, experimental bioactive glass substrates were coated with various polymer formulations in order to impart tunable surface features to the whole systems, which will act as models of the healthy and aged bone tissue once they have been colonized by cells.

Abstract: Powders of Mg_0.4Ca_0.6Fe₂O₄ were prepared by sol-gel using ethylene glycol and Mg, Ca and Fe nitrates as starting materials. Those powders were heat treated at different temperatures (300, 400, 500 and 600 °C) for 30 min. The materials obtained were characterized by X-ray diffraction (XRD) and vibrating sample magnetometry (VSM). The Ca-Mg ferrite with the most appropriate magnetic properties was further analyzed by transmission electron microscopy (TEM). The heating capability of the nanoferrites was also tested via magnetic induction. The XRD patterns of these Ca-Mg ferrites showed a cubic inverse spinel structure. Furthermore, neither traces of hematite nor orthorhombic Ca ferrite phases were detected. Moreover, all the Ca-Mg ferrites are superparamagnetic and the particle size distribution of these Ca-Mg magnetic nanoparticles exhibits an average diameter within the range of 10-14 nm. The needed temperature for hyperthermia treatment was achieved at around 12 min.

Abstract: Titania (TiO₂) nanotube gaining predominance as a bioceramic due to its excellent features such as high specific surface area and exhibiting appropriate cellular response. At present, we showed a conversion from titania nanoparticle to nanotube by hydrothermal treatment with 10M soduim hydroxide and 1M HCl solutions at 150°C over 48h. Then the sample annealed at various temperatures. Results indicate the reaction temperature is a main factor in determining the aspect ratio of the tubes. FESEM image conformed the synthesis of nanotube. In vitro study by using 150 °C-synthesized nanotube calcined at different temperatures are also presented establishing the potential of nanotubes in biomedical applications

Abstract: In an In vivo study the full synthetic bone substitute NanoBone^® S (NBS) was analyzed using a standardized bone defect (6 x 12 x 24mm) model in the ovine tibial metaphysis. The defect on the left side was filled with NBS granules and on the right side, autologous bone, harvested from the hip of the same animal, was inserted. After six, 12 and 26 weeks sheep were sacrificed and the tibiae analyzed. Quantitative histomorphological analysis after six weeks showed a resorption of biomaterial from over 60 to 24 percent. In contrast the bone formation after 6, and 12 weeks revealed an osteoneogenesis of 19%, and 34%, respectively. Hematoxylin and eosin sections demonstrated multinucleated giant cells on the surface of the biomaterial and resorption lacunae, indicating osteoclastic resorptive activity.

Abstract: The synthesis of nanoparticles appropriate for the preparation of nanostructured hydroxyapatite ceramics intended for bone repairs and regeneration is an interesting field of biomaterials research today. In this work nanoparticles of hydroxyapatite were obtained by the precipitation method using conventional magnetic stirring (A) and ultra turrex homogenizer (T1) accompanied with surfactant (T2) and dispersant agents (T3). In all cases, powders with nanometric dimensions were obtained and the unique calcium phosphate phase detected was hydroxyapatite (HAp). The powders sintering behaviour was studied. The ceramics obtained from powders prepared by magnetic stirring (A) showed the best values of final density (96.7 %) which it was in agreement with the lowest temperature of the beginning of shrinking (648.6 °C) during sintering determined by dilatometry. Nanostructured nature of these ceramics was confirmed by Scanning Electron Microscopy (SEM).

Abstract: Many people worldwide assess themselves as having halitosis, often caused by bio-film and microbial putrefaction of the debris in the mouth, leading to the production of mal-odorous compounds, volatile sulfur compounds (VSC) such as hydrogen sulfide (H₂S), methyl mercaptan and dimethyl sulfide. Some desulfurizing agents such as CaO and Na₂CO₃ in the industry are widely used, but there are few dental desulfurizing agents or adsorbents for removal of VSC. Ag ion exchanged zeolite material showed a high adsorptive property of H₂S in aqueous solution (H₂S water), however Ag sulfides were formed in aqueous solution. The VSC adsorption capabilities of layered double hydroxides, of which composition is A_1-xAl_x(OH)₂B_x/n·mH₂O, where A is Mg and/or Zn and B is CO₃^2-, in aqueous medium was studied by FPD/GC. The concentration of H₂S fell to 0% in 2 h when the Zn hydrotalcite was used, while that decreased to 20% in 18 h when the Mg hydrotalcite heated at 500 °C was used. The zinc ion was not detected in the H₂S water after soaking for 18 hours.The Zn hydtotalcite is expected to be likely adsorbent for the fast removal of VSC from the mouth.

Abstract: The use of bone substitutes for recovery of lost function is a constant search within the medical field. So biomaterials have received a very large attention from the scientific community, including the materials the basis of calcium phosphate. Hydroxyapatite (HA) has been studied as apart from representing the natural constitution of the mass of bones and teeth in 30 to 70 %, has properties of bioactivity and osteoconductivity, encouraging and assisting the growth of bone tissue. In contrast, bacterial infections can arise after implantation causing the loss of functionality in the short and medium term. Several alternatives are being tested, usually associated with the use of conventional antibiotics incorporated into biomaterials. An alternative to antibiotics would be use such metals that possess antibacterial properties. Silver (Ag) is known as a bactericidal metal and so gained a prominent place among the studies as an important ally in the control of post-surgical infections. This work aimed to synthesize, characterize and evaluate the antimicrobial effect of the addition of silver ions into hydroxyapatite. The hydroxyapatites containing silver were obtained by the precipitation method in aqueous solution containing AgNO₃ and by immersing the powder after the precipitation process in aqueous solutions containing AgNO₃. At this stage of the work, were analyzed and characterized the crystalline phases and the ionic groups present in HA, HA precipitates with Ag and immersed in a solution of Ag. X-ray diffraction (XRD) spectra showed that regardless of the method used, precipitation (room temperature or 90°C) or by immersion, the metallic Ag was present in the structure of HA. Additionally, it was observed that the peaks indicated in the XRD pattern for HA corresponding to the diffraction pattern of plugs JPCDS 09-0432 (Joint Committee on Powder Diffraction Standards). No peaks related to the phases being observed β-TCP and CaO, respectively, indicating that the conditions adopted for obtaining HA Ag, only HA phase is present and that methods, precipitation and immersion are efficient to occur doping of HA with Ag

Abstract: Pedicle screw (PS) system using Ti-6Al-4V PSs became popular in spinal instrumentation system. However, they sometimes case loosening and back-out from bone because of their poor bone-bonding ability. In the present study, Ti-6Al-4V alloy was subjected to the acid-heat or calcium-heat treatments that are effective for inducing high capacities of apatite formation and bone bonding on pure Ti. When the alloy was subjected to the acid-heat treatment, a surface layer composed of rutile and anatase TiO₂ enriched with Al and V was produced. Thus the treated alloy was neutrally charged and did not form apatite in a simulated body fluid (SBF) even after 3 day. In contrast, when the alloy was subjected to the Ca-heat treatment, a surface layer composed of calcium titanate, anatase and rutile free from Al and V was produced. The treated alloy formed apatite in SBF within 3 days. When the Ti-6Al-4V PSs subjected to the Ca-heat treatment was implanted into vertebra of beagle dogs, they showed higher bone-bonding ability as well as bone contact area than those without the treatment. This kind of bioactive Ti-6Al-4V PSs might be useful for spinal instrumentation since they could prevent loosening and back-out from bone.

Abstract: Micropores were formed on the surface of Ti-15Mo-5Zr-3Al alloy plate by doubled sandblasting process using silicon carbide particles with 14.0 μm and/or 3.0 µm average particle size by changing the combination of the size of particles. Apatite Nucleus (AN) was precipitated in the pores. By these treatments, bioactive AN precipitated Ti alloys were fabricated. Bioactivity of the Ti alloys was examined by soaking in SBF. Formed hydroxyapatite showed highest adhesive strength in the case of sandblasting using 14.0 μm particles then using 3.0 μm particles.