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Top-down tissue engineering aims to produce functional tissues using biomaterials as scaffolds, thus providing cues for cell proliferation and differentiation. Conversely, the bottom-up approach aims to precondition cells to form modular tissues units (building-blocks) represented by spheroids. In spheroid culture, adult stem cells are responsible for their extracellular matrix synthesis, re-creating structures at the tissue level. Spheroids from adult stem cells can be considered as organoids, since stem cells recapitulate differentiation pathways and also represent a promising approach for identifying new molecular targets (biomarkers) for diagnosis and therapy. Currently, spheroids can be used for scaffold-free (developmental engineering) or scaffold-based approaches. The scaffold promotes better spatial organization of individual spheroids and provides a defined geometry for their 3D assembly in larger and complex tissues. Furthermore, spheroids exhibit potent angiogenic and vasculogenic capacity and serve as efficient vascularization units in porous scaffolds for bone tissue engineering. An automated combinatorial approach that integrates spheroids into scaffolds is starting to be investigated for macro-scale tissue biofabrication.

A new study about corrosion behavior of CoCrMo alloy used as implant material exposed to the physiological serum and Hank's solution in different temperatures, electrolyte compositions and immersion time were simulated, using open circuit potential (OCP), potentiodynamic polarization curves (PPC) and electrochemical impedance spectroscopy (EIS.) From the results, it can be concluded that CoCrMo biomaterial is influenced by electrolyte composition and temperature, and the passive films were more protective when formed in presence of physiological serum. Comparing the Ecorr for both solutions, it is possible to verify that the Hank's solution presented values more negative for the two studied temperatures (25 and 37 °C), indicating a greater susceptibility to the corrosion process. Regarding the results of potentiodynamic polarization, the ipass, decreased as function of time, indicating a more protective passive film at 25 °C. In regards to the physiological serum, the highest ipass values at 37 ºC evidenced the formation of a less stable passive film. The different behavior of ipass in Hank's solution may be related to the competitiveness between a possible film of D-glucose and oxides of the alloy metals. EIS studies suggest that the film formed in presence of physiological serum is nobler than that with Hank's solution.

In the present work, we investigated the nanostructure of calcium phosphate films formed during the initial stages of deposition (between 30 and 240 s; deposition rate of 3.7 nm/min) by radio-frequency magnetron sputtering. The sputtering deposition parameters and the plasma energy were previously adjusted to produce nearly stoichiometric nanocrystalline hydroxyapatite films after 180 min. Grazing-incidence X-ray diffraction and X-ray photoelectron spectroscopy analyses revealed that the films formed in the initial stages were composed of an amorphous calcium phosphate phase with a Ca/P ratio Ca/P = 1.60 ± 0.12, which is close to that of hydroxyapatite. Using high-resolution transmission electron microscopy, we demonstrated that the films were not a unique amorphous phase. An additional phase composed of dense calcium phosphate nanospheres was found in all periods and investigated. The nanospheres grew in size as the deposition time increased, and small nanospheres were always observed. This observation suggests the continuous formation of nanospheres at the surface of the film. Nanocrystalline regions were revealed by electron diffraction and high-resolution electron microscopy after a deposition of 60 s with a corresponding film thickness of 3.7 nm. Electron energy-loss spectroscopy analysis comparing individual nanospheres to the amorphous calcium phosphate layer showed differences in the oxygen K edge, suggesting a difference in the chemical bonding of the oxygen species. Nanospheres were observed in association with isolated crystals, suggesting that the nanospheres may participate in the crystallization of hydroxyapatite according to a heterogeneous nucleation process.

Various synthetic bone substitutes have been developed to reconstruct bone defects. One of the most prevalent ceramics in bone treatment is hydroxyapatite (HA) that is a useful material as bone substitute, however, with a low rate of biodegradation. Its structure allows isomorphic cationic and anionic substitutions to be easily introduced, which can alter the crystallinity, morphology, biocompatibility, and osteoconductivity. The objective of this study was to investigate the in vitro and in vivo biological responses to strontium-containing nanostructured carbonated HA/sodium alginate (SrCHA) spheres (425

The use of nanotechnology - especially in the area of human health - is increasing every day, with the application of various materials such as hydroxyapatite being amongst the most studied. Consequently, the affinity of hydroxyapatite compatible with so many applications in the human body is evolving cutting edge technology - the result of which is nanoparticles. However, despite these important

A radio-frequency magnetron sputtering technique operating in right-angle geometry (RAMS) with high plasma confinement was revised to produce thin films (15–570 nm) of fluorine-substituted hydroxyapatite, FHA, adapted to be used as nano-coatings for biomedical implants. An electron temperature of T eff ≈ 9.0 eV and a plasma electron density of 1.2 × 10 15 m − 3 assured the nucleation of an amorphous fluorine-substituted hydroxyapatite phase on Si and Ti surfaces. With the aid of a Langmuir probe, the RAMS plasma energy was tuned to control the coating stoichiometry and the ratio between the crystalline and amorphous phases. The energy delivered over time from the bombardment of ions and electrons transformed the amorphous calcium phosphate phase into crystalline fluorine-substituted hydroxyapatite. The crystalline films were obtained at room temperature. The partial substitution of OH − for F − in the HA structure was confirmed by X-ray diffraction using synchrotron radiation in grazing-incidence mode, X-ray photoelectron spectroscopy and attenuated total reflection Fourier transform infrared spectroscopy. High-resolution transmission electron microscopy carried out on cross-section film samples prepared by a focused ion beam (FIB) technique revealed that the film ultrastructure was composed of columnar crystals oriented perpendicularly to the substrate surface. The crystals were connected to the substrate surface by ordered nanolayers, indicating the existence of a continuous binding between the two materials. This work demonstrates that the RAMS technique is able to produce FHA nano-coatings with controlled chemical compositions and structures on metallic implants for clinical applications.

Synthetic hydroxyapatite (HA) is a widely used ceramic biomaterial due to its well described biocompatibility. Some modifications in HA surface can be made to increase surface porosity. Likewise, HA can be modified by the coating with proteins, which may impact on biocompatibility. In this work, we aimed to evaluate the impact of two surface modifications – coating with albumin, a major serum protein, and augmented porosity - over osteoblast adhesion on stoichiometric HA discs. Dense HA discs were obtained by pressing HA powder at 30 KN and sinterization at 1000°C, while porous HA was molded after the addition of alginate (15:1), followed by thermal treatment. Protein adsorption was attained by incubation on 0.5mg/mL bovine serum albumin (BSA) for 24 h at 37°C. MC3T3 mouse preosteoblasts were seeded over both protein-coated and uncoated dense or porous tablets, and cell viability after 24 h was estimated by XTT and Neutral Red assays. Cell density was quantified by fluorescence microscopy. While both dense and porous discs presented altered surfaces after protein treatment, as observed by scanning electron microscopy, porous HA tablets presented significantly higher levels of adsorbed protein. There was a decrease in the concentration of calcium ions in all samples analyzed. Porous HA treated with protein presented significant higher mitochondrial dehydrogenase activity (XTT) than non treated tablets (p

Hydroxyapatite is the main ceramic material that has being used in bone repair, although its physico-chemical and in vivo behavior should be better understood. A method to improve the biocompatibility of HA is the substitution of calcium with divalent cations which enhance mechanic resistance and can modulate inflammatory response against implanted material. In this study we analyzed the biocompatibility of HA doped with one per cent of Zn2+ or Pb2+. The first one has being described as an inflammation modulator and the second would be a model for chronic toxicity assay. Biocompatibility of the both materials was studied in vivo following the ISO 10993-6 standard. HA cylinders (ZnHA, PbHA and stoichiometric HA as positive control) were implanted into subcutaneous tissue of 45 Balb-c mice and after 1, 3 and 9 weeks the animals were euthanized (5 for each experimental condition). Necropsies of the skin containing reactional tissue were removed, fixed in 10% formaldehyde and followed the histological processing for paraffin embedding and staining with Hematoxylin-Eosine and Picrosirius red. Microscopic analysis showed for all groups moderate inflammatory response, decreasing throughout the experimental periods, with ZnHA group showing more intense response. Similar presence of macrophages, fibrosis and angiogenesis were observed among the groups. Thereby, we can conclude that ZnHA and PbHA are biocompatible and not bioresorbable, being the ZnHA potentially indicated as bone graft. Detailed studies are required to better understand the role of PbHA as chronic model for lead toxicity.

Bone tissue in ideal conditions morphofunctional remodeling properly. The bone can be affected by fractures, tumors, hormonal dysfunction, senescence, genetic modifications, among others. In such circumstances, the proper diet, drug use, exercise and other factors are important to the prevention of bone mineral loss. The effect of kinesiotherapy obtained through the application of vibratory waves administered through the vibrating platform, Juvent1000 ® already been established in the prevention of bone mineral density, muscular trophism, among other systems in humans. The response by analyzing bone tissue of bone repair in critical defect is not known in experimental animals and in human clinical. This research evaluated the osteogenic potential critical defect in the calvaria of rats subjected to the application of vibratory waves obtained by vibrating platform and implant in the critical defect of rat calvaria. The bone tissue response was evaluated showed satisfactory results obtained in biological points 15, 45 and 120 days.

The properties of the biodegradation of bone substitutes in the dental socket after extraction is one of the goals of regenerative medicine. This double-blind, randomized, controlled clinical trial aimed to compare the effects of a new bioabsorbable nanostructured carbonated hydroxyapatite (CHA) with a commercially available bovine xenograft (Bio-Oss&reg, ) and clot (control group) in alveolar preservation. Thirty participants who required tooth extraction and implant placement were enrolled in this study. After 90 days, a sample of the grafted area was obtained for histological and histomorphometric evaluation and an implant was installed at the site. All surgical procedures were successfully carried out without complications and none of the patients were excluded. The samples revealed a statistically significant increase of new bone formation (NFB) in the CHA group compared with Bio-Oss&reg, after 90 days from surgery (p &lt, 0.05). However, the clot group presented no differences of NFB compared to CHA and Bio-Oss&reg, The CHA group presented less amount of reminiscent biomaterial compared to Bio-Oss&reg, Both biomaterials were considered osteoconductors, easy to handle, biocompatible, and suitable for alveolar filling. Nanostructured carbonated hydroxyapatite spheres promoted a higher biodegradation rate and is a promising biomaterial for alveolar socket preservation before implant treatment.

It was recently shown that the crystallinity of extracted bone mineral samples from the fin bones of zebrafish could increase over storage time. This would have implications in many studies in which the samples need to be stored until analysis. The aim of this study was to further evaluate if the crystallinity of extracted bone mineral increases over storage time. The extracted mineral was a biological bone-like apatite produced in osteoblast cell cultures. The overall characterization of the mineral was done by energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and high-resolution transmission electron microscopy. In order to evaluate possible changes in crystallinity over storage time, the same sample was analyzed by X-ray diffraction immediately after mineral extraction and after 18 months of storage. In conclusion, no statistically relevant changes were observed over storage time, although the occurrence of a slight increase in crystallinity could be discussed in the stored mineral sample.

This study investigates the long-term biocompatibility of 0.5 % zinc-containing hydroxyapatite compared with hydroxyapatite. Spheres (425 < ∅ < 550) of both materials were produced by extrusion of ceramic slurry in calcium chloride and characterized by FTIR, XRD, XRF and SEM. Fifteen White New Zealand rabbits were submitted to general anesthesia, and an perforation (2 mm), was made in each tibia, one for zinc-containing hydroxyapatite sphere implantation and one for hydroxyapatite sphere implantation. After 26, 52 and 78 weeks, the animals were euthanized, and the fragment containing the biomaterial was harvested. A 30–50 μm section was obtained for histological analysis in bright field and polarized light. SEM images revealed similar morphologies between the tested biomaterials. Histological analysis showed that there was no difference between the test groups. The morphometric analysis, however, indicates that there was a greater absorption. The materials are biocompatible, promote osteogenesis and that the zinc-containing hydroxyapatite microspheres were absorbed more quickly.

In this work, the synthetic hydroxyapatite (HAP) was studied using different preparation routes to decrease the crystal size and to study the temperature effect on the HAP nano-sized hydroxyapatite crystallization. X-ray diffraction (XRD) analysis indicated that all samples were composed by crystalline and amorphous phases . The sample with greater quantity of amorphous phase (40% of total mass) was studied. The nano-sized hydroxyapatite powder was heated and studied at 300, 500, 700, 900 and 1150 °C. All samples were characterized by XRD and their XRD patterns refined using the Rietveld method. The crystallites presented an anisotropic form, being larger in the (001) direction. It was observed that the crystallite size increased continuously with the heating temperature and the eccentricity of the ellipsoidal shape changed from 2.75 at 300 °C to 1.94, 1.43, 1.04 and 1.00 respectively at 500, 700, 900 and 1150 °C. In order to better characterize the morphology of the HAP the samples were also examined using atomic force microscopy (AFM), infrared spectrometry (IR) and thermogravimetric analysis (TGA).

We report the ultrastructure of regenerated bone surrounding two types of biomaterials: hydroxyapatite–alginate composite and sintered hydroxyapatite. Critical defects in the calvaria of Wistar rats were filled with micrometer-sized spherical biomaterials and analyzed after 90 and 120 days of implantation by high-resolution transmission electron microscopy and Fourier transform infrared attenuated total reflectance microscopy, respectively. Infrared spectroscopy showed that hydroxyapatite of both biomaterials became more disordered after implantation in the rat calvaria, indicating that the biological environment induced modifications in biomaterials structure. We observed that the regenerated bone surrounding both biomaterials had a lamellar structure with type I collagen fibers alternating in adjacent lamella with angles of approximately 90°. In each lamella, plate-like apatite crystals were aligned in the c-axis direction, although a rotation around the c-axis could be present. Bone plate-like crystal dimensions were similar in regenerated bone around biomaterials and pre-existing bone in the rat calvaria. No epitaxial growth was observed around any of the biomaterials. A distinct mineralized layer was observed between new bone and hydroxyapatite–alginate biomaterial. This region presented a particular ultrastructure with crystallites smaller than those of the bulk of the biomaterial, and was possibly formed during the synthesis of alginate-containing composite or in the biological environment after implantation. Round nanoparticles were observed in regions of newly formed bone. The findings of this work contribute to a better understanding of the role of hydroxyapatite based biomaterials in bone regeneration processes at the nanoscale.

High-resolution transmission electron microscopy (HRTEM) and ab initio quantum-mechanical calculations of electronic structure were combined to investigate the structure of the hydroxyapatite (HA) (0 1 0) surface, which plays an important role in HA interactions with biological media. HA was synthesized by in vitro precipitation at 37 °C. HRTEM images revealed thin elongated rod nanoparticles with preferential growth along the [0 0 1] direction and terminations parallel to the (0 1 0) plane. The focal series reconstruction (FSR) technique was applied to develop an atomic-scale structural model of the high-resolution images. The HRTEM simulations identified the coexistence of two structurally distinct terminations for (0 1 0) surfaces: a rather flat Ca(II)-terminated surface and a zig-zag structure with open OH channels. Density functional theory (DFT) was applied in a periodic slab plane-wave pseudopotential approach to refine details of atomic coordination and bond lengths of Ca(I) and Ca(II) sites in hydrated HA (0 1 0) surfaces, starting from the HRTEM model.

This work evaluates the suitability of biphasic calcium phosphate (BCP) granules (β-TCP/HA 70:30) as potential carriers for cell-guided bone therapy. The BCP granules were obtained by synthesis in the presence of wax, thermal treatment, crushing and sieving and characterized by scanning electron microscopy (SEM), X-ray diffraction and Fourier transform infrared spectroscopy. The cytocompatibility of the BCP granules was confirmed by a multiparametric cytotoxicity assay. SEM analysis showed human bone cell adhesion and migration after seeding onto the material. Rat subcutaneous xenogeneic grafting of granules associated to human bone cells revealed a more accentuated moderate chronic inflammatory infiltrate, without signs of a strong xenoreactivity. Histomorphometrical analysis of bone repair of defects in rat skulls (∅ = 5 mm) has shown that bone cell associated-BCP and autograft promoted a two- and threefold increase, respectively, on new bone formation after 45 days, as compared to BCP alone and blood clot. The increase in bone repair supports the suitability the biocompatible (70:30) BCP granules as injectable and mouldable scaffolds for human cells in bone bioengineering.

Hydroxyapatite (HA) is largely used as bone graft; it seems to be the most promising synthetic implant material, mainly because of its excellent biocompatibility. The crystallinity, particle and pore size of HA are important characteristics and can be modified by decreasing basic structural form below 100 nm and have evoked a great amount of attention for improving prevention, diagnosis, and disease treatment, besides improving bone repair through the biodegradation of the material. The aim of this study was to investigate bone mineral content in bone samples with nanohydroxyapatite and HA spheres, specially its spatial distribution on bone microarchitecture. Circular bone defects were made in both tibiae of 12 White New Zeland adult rabbits (Oryctolagus cuniculus) and were divided randomly into five groups – blood clot (control group), sintered HA, non-sintered HA, sintered nanoHA and non-sintered nanoHA – all materials in spherical shape, to smooth handling and accommodation of the surgical bed, and to minimize inflammatory response. The rabbits were euthanatized according to the experimental period of 1 and 4 weeks after surgery. The samples were evaluated by polarized microscopy as well as X-ray microfluorescence in order to account the bone mineral content bone-implant interfaces, through synchrotron radiation. Our results revealed greater newly formed bone area in the non-sintered materials and control groups, and the used technique showed that the amount of calcium of new bone was consistent with both mature bone and HA spheres. In conclusion, the present findings suggest that HA-based biomaterials are biocompatible, promote osteoconduction and favored bone repair. Copyright © 2011 John Wiley & Sons, Ltd.

Carbonated apatite (CHA) is commonly considered a promising synthetic material for biomedical applications in orthopedic and dental surgery due to its biocompatibility, bioresorption and bioactivity. CHA5, CHA37 and CHA90 powders were synthesized from wet method and the DRX patterns showed that the crystallinity and particle size of CHA samples increased proportionally with the synthesis temperature. Powder extracts medium were obtained from each sample to interact with MC3T3-E1 osteoblastics cells. It was evaluated morphology, citotoxicity, pH and Ca2+ concentration. Citotoxicity assays showed high metabolic activity on all samples when compared to control. The polygonal shaped and the confluent monolayer observed in control cells progressively changed according to the crystallinity increase of samples. Cells under mitosis and spindle-like shaped where the main alterations observed. In addition the cell viability could be sensitive to the acid reactivity and crystallinity of carbonated apatite samples.

Cell adhesion, proliferation and differentiation are important specific parameters to be evaluated on biocompatibility studies of candidate biomaterials for clinical applications. Several different methodologies have been employed to study, both qualitative and quantitatively, the direct interactions of ceramic materials with cultured mammal and human cells. However, while quantitatively evaluating cell density, viability and metabolic responses to test materials, several methodological challenges may arise, either by impairing the use of some widely applied techniques, or by generating false or conflicting results. In this work, we tested the inherent interference of different representative calcium phosphate ceramic surfaces (stoichiometric dense and porous hydroxyapatite (HA) and cation-substituted apatite tablets) on different tests for quantitative evaluation of osteoblast adhesion and metabolism, either based on direct cell counting after trypsinization, colorimetric assays (XTT, Neutral Red and Crystal Violet) and fluorescence microscopy. Cell adhesion estimation after trypsinization was highly dependent on the time of treatment, and the group with the highest level of estimated adhesion was inverted from 5 to 20 minutes of exposition to trypsin. Both dense and porous HA samples presented high levels of background adsorption of the Crystal Violet dye, impairing cell detection. HA surfaces also were able to adsorb high levels of fluorescent dyes (DAPI and phalloidin-TRITC), generating backgrounds which, in the case of porous HA, impaired cell detection and counting by image processing software (Image Pro Plus 6.0). We conclude that the choice for the most suitable method for cell detection and estimation is highly dependent on very specific characteristics of the studied material, and methodological adaptations on well established protocols must always be carefully taken on consideration.

The kinetic of chlorhexidine digluconate (CHXDG) uptake from aqueous solution by hydroxyapatite (HA) was investigated by ultraviolet (UV) analysis performed in HA powder (UV-solid) after the CHX adsorption. Adsorption isotherm of chlorhexidine (CHX) uptake was modeled by a combination of Languimir and Langmuir–Freundlich mechanisms. Strong molecule–molecule interactions and positive cooperativity predominated in the surface when CHX concentration was above 8.6 μg CHX /mg HA . UV-solid spectra (shape, intensity and band position) of CHX bound to HA revealed that long-range molecular structures, such as aggregates or micelles, started to be formed at low CHX concentrations (1.52 μg CHX /mg HA ) and predominated at high concentrations. Grazing-incidence X-ray diffraction (GIXRD) analysis from synchrotron radiation discarded the formation of crystalline structures on HA surface or precipitation of CHX crystalline salts, as suggested in previous works. The effect of the HA/CHX association on HA in vitro bioactivity, cytotoxicity and CHX antimicrobial activity was evaluated. It was shown that CHX did not inhibit the precipitation of a poorly crystalline apatite at HA/CHX surface after soaking in simulating body fluid (SBF). Cell viability studies after exposure to extracts of HA and HA/CHX showed that both biomaterials did not present significant in vitro toxicity. Moreover, HA/CHX inhibited Enterococcus faecalis growth for up to 6 days, revealing that binding to HA did not affect antimicrobial activity of CHX and reduced bacterial adhesion. These results suggested that HA/CHX association could result in a potential adjuvant antimicrobial system for clinical use.

In this work myoglobin (Mb) adsorption was carried out in a batch system using hydroxyapatite (HA) powder during 24 hours at 37°C. The HA samples were analyzed after protein adsorption by Fourier Transformed Infrared (FTIR) and UV-Vis Spectroscopy in reflectance mode. UV-Vis analyses showed that Soret and Q bands shifted to lower wavelengths when Mb is associated with HA surface. This result suggests that Mb Heme group is sensitive to the protein adsorption onto HA surface. HA disks coated with myoglobin and cultured with human osteoblastic cells during 7 days showed that cell adhesion and proliferation were not inhibited by the protein coating after 7 days in cell culture.

Bovine serum albumin (BSA) may have an inhibitory or promoter effect on hydroxyapatite (HA) nucleation when apatite is precipitated in a medium containing the protein. In this study we evaluated the influence of BSA on the precipitation of calcium phosphate phases (CP) from simulated body fluid (SBF) when the protein was previously bounded to HA surface. The kinetics of BSA immobilization onto hydroxyapatite surface was performed in different buffers and protein concentrations in order to adjust experimental conditions in which BSA was tightly linked to HA surface for long periods in SBF solution. It was shown that for BSA concentration higher than 0.1mg/mL the adsorption to HA surface followed Langmuir–Freundlich mechanisms, which confirmed the existence of cooperative protein–protein interactions on HA surface. Fourier Transformed Infrared Attenuated Total Reflectance Microscopy (FTIRM-ATR) evidenced changes in BSA conformational state in favor of less-ordered structure. Analyses from high resolution grazing incident X-ray diffraction using synchrotron radiation (GIXRD), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) showed that a poorly crystalline calcium phosphate was precipitated on the surface of HA discs coated with BSA, after the immersion in SBF for 4 days. The new bioactive layer had morphological characteristics similar to the one formed on the HA surface without protein. It was identified as a carbonated apatite with preferential crystal growth along apatite 002 direction. The GIXRD results also revealed that BSA layer bound to the surface inhibited the HA dissolution leading to a reduction on the formation of new calcium phosphate phase.

Well characterized kaolin samples from different deposits of Brazil were studied by electron paramagnetic resonance. Three paramagnetic species attributed to iron in different chemical environments were identified in raw samples. A very intense and broad line with 0.2 mT linewidth was typical of large particles of iron oxides/hydroxides. A species at g = 2.0 with 0.04 mT line width was associated with superparamagnetic particles adsorbed to kaolinite surfaces or trapped between its lamellae. An isotropic and/or orthorhombic species in the g = 4.2 region belongs to structural Fe 3+ replacing Al 3+ in sites with different crystal-field symmetries. It was verified that large iron oxide particles were responsible for keeping the kaolin whiteness at levels below 50%. Superparamagnetic iron particles mainly affect whiteness in the range of 50% 86%) were determined by Fe 3+ iron content in the kaolinite structure. However, only a small part of this species can be removed from the kaolinite structure by traditional industrial processing techniques. These results showed that EPR is a powerful technique to assist in controlling kaolin quality in industrial processes.

The corrosion resistance of Ti and Ti–6Al–4V was investigated through electrochemical impedance spectroscopy, EIS, potentiodynamic polarisation curves and UV–Vis spectrophotometry. The tests were done in Hank solution at 25 °C and 37 °C. The EIS measurements were done at the open circuit potential at specific immersion times. An increase of the resistance as a function of the immersion time was observed, for Ti (at 25 °C and 37 °C), and for Ti–6Al–4V (at 25 °C), which was interpreted as the formation and growth of a passive film on the metallic surfaces.

Polycrystalline solid solution of phosphate and vanadate lead calcium apatites Pb 10 -x Ca x( VO 4)1( PO 4)5( OH )2 apatites [x = 0.0, 2.0, 4.0, 6.0, 8.0, and 10.0] was reduced with hydrogen gas at the temperature of 300 and 400°C for 1 h. All these compounds were investigated by XRD and ESR spectroscopy. Only one reduced oxidation state V +4 was detected. Two types of species like isolated vanadium (+4) and clusters of V 4+ had been observed. The stability of the apatites increases and the particle size of the crystal decreases with calcium doping concentrations. As the concentrations of Ca increase the intensity of ESR lines deviates due to the spin–lattice relaxation interactions. The deviation in the intensity of ESR spectra can be attributed as the coexistence of paramagnetic and antiferromagnetic phases in the apatites.

Tissue engineering is a multidisciplinary research area that aims to develop new techniques and/or biomaterials for medical applications. The objective of the present study was to evaluate the osteogenic potential of a composite of hydroxyapatite and alginate in bone defects with critical sizes, surgically made in the calvaria region of rats. The rats (48 adult males), Rattus norvegicus Wistar, were divided into two groups: control (without composite implantation) and experimental (with composite implantation) and analyzed by optical microscopy at the biological time points 15, 45, 90 and 120 d, and transmission electron microscopy 120 d after the implantation of the biomaterial. It was observed that the biomaterial presented a high degree of fragmentation since the first experimental points studied, and that the fragments were surrounded by new bone after the duration of the project. These areas were studied by analytical transmission electron microscopy using an energy dispersive X-ray spectrometer. Three regions could be distinguished: (1) the biomaterial rich in hydroxyapatite; (2) a thin contiguous region containing phosphorus but without calcium; (3) a region of initial ossification containing mineralizing collagen fibrils with a calcium/phosphorus ratio smaller than the particles of the composite. The intermediate region (without calcium or containing very low amounts of calcium), which just surrounded the composite had not been described in the literature yet, and is probably associated specifically to the biocomposite used. The high performance of the biomaterial observed may be related to the fact that alginate molecules form highly anionic complexes and are capable of adsorbing important factors recognized by integrins from osteoblasts. Regions of fibrotic tissue were also observed mainly in the initial experimental points analyzed. However, it did not significantly influence the final result. In conclusion, the biomaterial presents a great potential for application as bone grafts in the clinical area.

First-principles modeling combined with experimental methods were used to study hydroxyapatite in which Sr2+ is substituted for Ca2+. Detailed analyses of cation-oxygen bond distributions, cation-cation distances, and site 1-oxygen polyhedron twist angles were made in order to provide an atomic-scale interpretation of the observed structural modifications. Density functional theory periodic band-structure calculations indicate that the Ca2+ to Sr2+ substitution induces strong local distortion on the hydroxyapatite lattice: the nearest neighbor Sr-O bond structures in both cationic sites are comparable to pure SrHA, while Sr induces more distortion at site 2 than site 1. Infrared vibrational spectroscopy (FTIR) and extended X-ray absorption fine structure (EXAFS) analysis suggest increasing lattice disorder and loss of OH with increasing Sr content. Rietveld refinement of synchrotron X-ray diffraction patterns shows a preference for the Ca1 site at Sr concentrations below 1 at.%. The ideal statistical occupancy ratio Sr2/Sr1=1.5 is achieved for approximately 5 at.%; for higher Sr concentrations occupation of the Ca2 site is progressively preferred.

Biomaterials for treatment of bone defects have been studied for a long time. Alloplastic materials, mainly hydroxyapatite (HA), are under intense investigation due to its biocompatibility and osteoconductive properties. The HA can be modified by the incorporation of bivalent cations as Zn2+ known as a positive effectors for bone repair. The purpose of this study was to evaluate comparatively the effectiveness of 5% zinc-containing hydroxyapatite (ZnHA) in the treatment of critical size defect (CSD) in rat’s calvaria. CSD (8mm diameter) created in the skull of forty-five Wistar rats were filled with autogenous bone, HA and ZnHA. Skulls harvested after 30, 90 and 180 days were submitted to histological processing for paraffin embedding. Sections of 5 µm-thick stained with hematoxylin and eosin (HE) allowed histomorphometric analysis. The area of neoformed bone increased (p

In this work we applied a new route to synthesize magnetic iron oxide nanoparticles into alginate polymer for future application as drug delivery system activated by magnetic external stimuli. Calcium-alginate was used to encapsulate iron oxide nanoparticles, and as scaffold for particle nucleation and its influence on particles size and magnetic properties were studied. The iron oxide mean sizes were between 4.3 and 9.5 nm. Iron is dispersed throughout the polymer matrix mainly as iron oxide particles, and a small fraction as iron (III) occupying calcium sites in the polymer network. The temperature dependence of the Mossbauer spectra is typical of superparamagnetic particles in agreement with the magnetic susceptibility data.

Phosphates have been used for lead immobilization in soils but the influence of soil type is not fully understood. In this work, lead chemical behaviour in two Brazilian latosoils (LA and LV) was studied via treatment with phosphates. The Pb concentration in Toxicity Characteristic Leaching Procedure (TCLP) solutions was decreased in all treatments. After treatment with H3PO4 the Pb concentration in the LA remained within the regulatory limit established by EPA. The ecotoxicological results with Daphnia pulex showed that this treatment reduced the lead bioavailability. Sequential extraction analyses showed that the lead was transferred from the most available to the residual fraction. Relevant decrease of soluble lead was observed in all phosphate treatments. Made available in DSpace on 2016-10-06T22:35:54Z (GMT). No. of bitstreams: 1 a22v31n3.pdf: 551611 bytes, checksum: 262644b27af3b01a0950fe4cbfce3d81 (MD5) Previous issue date: 2008-12-03

Millimetric spherical beads of a biocompatible composite were produced from sodium alginate, a natural polysaccharide, and nanostructured hydroxyapatite (HA). It was shown that the composite was effective in the removal of lead ions and lead phosphate nanoparticles from high-contaminated simulated gastric fluid. X-ray diffraction spectroscopy and scanning electron microscopy analyses performed on HA–alginate beads after the Pb2+ uptake showed that nanocrystals of a lead phosphate, [Pb10–xCax(PO4)6Cl2], were precipitated on the bead surface. The cross-linked polymer chain had a double role: (i) keep Pb2+ ions and lead phosphate nanoparticles bounded to the bead surface, preventing their bioavailability in stomach fluid; and (ii) delay HA dissolution in the acidic conditions of the stomach, assuring that an excess of Ca2+ will not be released to simulated gastric fluid. Desorption experiments in simulated enteric fluid revealed that lead remained immobilized in the calcium phosphate phase in the intestinal tract. These results indicate HA–alginate composite as a potential system for heavy metals removal from contaminated gastric and enteric human fluids, minimizing its adsorption by the human body.

Hydroxyapatite (HA), widely used as bone graft, can be modified by the incorporation of bivalent cations (Mg2+ and Zn2+) and its gradual release could favor the bone repair. The purpose of this research was to evaluate the effect of the HA and zinc-containing hydroxyapatite (Zn-HA) in the bone repair in rat calvaria in comparison to autogenous bone. Critical size defect in the calvaria was filled with the graft material and the samples were harvested at the 30, 90 and 180 days. The light microcopy observations showed the biocompatibility of the graft materials. In the Zn-HA group the area of neoformed bone was larger than in the HA group, but smaller than in the autograft. A fibrous connective tissue was more evident around HA granules. It could be conclude that the presence of zinc ions in HA crystal accelerated the osteogenesis and increased the area of newly formed bone in relation to HA.

Crystalline hydroxyapatite thin coatings have been prepared using a novel opposing RF magnetron sputtering approach at room temperature. X-ray diffraction (XRD) analysis shows that all the principal peaks are attributable to HA, and the as-deposited HA coatings are made up of crystallites in the size range of 50-100nm. Fourier transform infrared spectroscopy (FTIR) studies reveal the existence of phosphate, carbonate and hydroxyl groups, suggesting that HA coatings are highly crystalline. To study the biocompatibility of these coatings, murine osteoblast cells were seeded onto various substrates. Cell density counts using fluorescence microscopy show that the best osteoblast proliferation is achieved on an HA RAMS-coated titanium substrate. These experiments demonstrate that RAMS is a promising coating technique for biomedical applications.

A solid solution of phosphate and vanadate lead apatites Pb 10( PO 4)6-x( VO 4)x( OH )2 (x = 0.5, 1.0, 2.0, 3.0, and 6.0) were reduced with hydrogen gas at temperature 300°C for one hour. All these compounds were investigated by XRD and ESR spectroscopy. Only one reduced oxidation state, V 4+, was detected. Two types of species-like isolated vanadium (+ 4) and clusters of V 4+ were observed. The EPR powder spectrum computer simulations were performed using the program Simfonia from Bruker. Spin Hamiltonian parameters were also calculated. As the concentrations of vanadium ions increase to 2.0, the intensity of the ESR lines increases, and x = 3.0 the intensity of the ESR line decreases sharply. After this concentration, i.e. x > 3.0, there is again an increase in the intensity. The variation of the line shape and intensity of the ESR spectra can be attributed to increases in the hopping rate of the charge carriers (polarons) in different apatite compositions.

Spin–lattice relaxation times, T 1 , for EPR signals created by irradiation of tooth enamel or carbonate-doped hydroxyapatite were studied by three-pulse inversion recovery and long-pulse saturation recovery. The recovery curves were modeled as the sum of two log-normal distributions of relaxation times. The dominant component in the EPR signal for tooth samples is assigned to CO 2 - replacing phosphate (B-sites) in the hydroxyapatite matrix. For this component the center of the T 1 distribution was 1.4 – 1.6 μ s at 294 K, and did not vary significantly with radiation dose or the source of the sample. The smaller, slower relaxing, component of the signals from the tooth samples had a T 1 distribution centered at 30 – 60 μ s and is assigned to an organic radical ( g ∼ 2.0045 ) . At 294 K the spin–spin relaxation time T 2 measured by two-pulse echo decay was dominated by motion of the CO 2 - and was independent of dose. The dose independence of T 1 and T 2 at ambient temperature provides the basis for using dose-independent microwave powers to record dosimetric tooth signals at microwave powers above the linear response regime.

Hydroxyapatite (HA) films have been widely recognized for their biocompatibility and utility in promoting biointegration of implants in both osseous and soft tissue. Conventional sputtering techniques have shown some advantages over the commercially available plasma spraying method; however, the as-sputtered films are usually amorphous which can cause some serious adhesion problems when post-deposition heat treatment is necessitated. In this paper we present an opposing radio frequency (RF) magnetron sputtering approach for the preparation of HA thin films on various substrates at low power levels. Using this alternative RF magnetron geometry, as-sputtered HA films are nearly stoichiometric, highly crystalline, and strongly bound to the substrate. Post-deposition heat treatment under 800 °C did not result in a marked improvement in the degree of crystallinity of the films. In addition, dissolution experiments show that as-sputtered films are more stable than annealed ones. As-sputtered films grown on amorphous silica substrates exhibit X-ray diffraction (XRD) patterns similar to those of randomly orientated HA powder. On the other hand, films deposited on oriented substrates such as Si(100) and Si(111) show a polycrystalline HA XRD pattern but with some strongly preferred orientations, indicating that HA crystallization is sensitive to the nature of the substrate. The results suggest that the opposing RF magnetron sputtering approach has some potential to produce high quality HA films on metallic implants.

The aim of this study is to evaluate the biocompatibility and osteoconductivity in surgical defects of sheep tibias filled with 1% strontium-containing nanostructured hydroxyapatite microspheres (SrHA), stoichiometric hydroxyapatite without strontium microspheres (HA), or blood clots. Santa Ines sheep were subjected to three perforations on the medial side of the left tibia. The biomaterials were characterized by X-ray Diffraction (XRD) and Fourier Transform Infrared (FTIR) before implantation and by X-Ray Microfluorescence (µFRX) and Scanning Electron Microscopy (SEM) after sheep tibias implantation. Surgical defects were filled with blood clots (control), SrHA (Group 1) or HA (Group 2). After 30 days, 5-µm bone blocks were obtained for histological evaluation, and the blocks obtained from 1 animal were embedded in methylmethacrylate for undecalcified sections. Mononuclear inflammatory infiltrate remained mild in all experimental groups. Giant cells were observed surrounding biomaterials particles of both groups and areas of bone formation were detected in close contact with biomaterials. All groups showed newly formed bone from the periphery to the center of the defects, which the control, HA and SrHA presented 36.4% (± 21.8), 31.2% (± 14.7) and 26.2% (± 12.9) of newly formed bone density, respectively, not presenting statistical differences. In addition, the connective tissue density did not show any significant between groups. The SrHA showing a higher volume density of biomaterial (51.2 ± 14.1) present in the defect compared to HA (32.6 ± 8.5) after 30 days (p = 0.03). Microspheres containing 1% SrHA or HA can be considered biocompatible, have osteoconductive properties and may be useful biomaterials for clinical applications.

Hydroxyapatite (HA) has been investigated as a delivery system for antimicrobial and antibacterial agents to simultaneously stimulate bone regeneration and prevent infection. Despite evidence supporting the bactericidal efficiency of these HA carriers, few studies have focused on the effect of this association on bone regeneration. In this work, we evaluated the physico-chemical properties of hydroxyapatite microspheres loaded with chlorhexidine (CHX) at two different concentrations, 0.9 and 9.1 $$\upmu {\text{g}}_{\text{CHX}} /{\text{cm}}^{ 2}_{\text{HA}}$$ , and characterized their effects on in vitro osteoblast viability and bone regeneration. Ultraviolet–visible spectroscopy, scanning and transmission electron microscopy associated with energy-dispersive X-ray spectroscopy and electron energy loss spectroscopy were used to characterize the association of CHX and HA nanoparticles. The high CHX loading dose induced formation of organic CHX plate-like aggregates on the HA surface, whereas a Langmuir film was formed at the low CHX surface concentration. Quantitative evaluation of murine osteoblast viability parameters, including adhesion, mitochondrial activity and membrane integrity of cells exposed to HA/CHX extracts, revealed a cytotoxic effect for both loading concentrations. Histomorphological analysis upon implantation into the dorsal connective tissues and calvaria of rats for 7 and 42 days showed that the high CHX concentration induced the infiltration of inflammatory cells, resulting in retarded bone growth. Despite a strong decrease in in vitro cell viability, the low CHX loading dose did not impair the biocompatibility and osteoconductivity of HA during bone repair. These results indicate that high antimicrobial doses may activate a strong local inflammatory response and disrupt the long-term osteoconductive properties of CHX-HA delivery systems.

In this work Brazilian phosphate rocks, PRs, were used to reduce Pb2+, Cu2+ and Cd2+ concentrations from aqueous solutions. We concluded that these metals were mainly immobilized by fluorapatite but other minerals such as calcium carbonate also contribute to their immobilization. In the case of lead two mechanisms are proposed: the Ca10(PO4)6F2 dissolution followed by the precipitation of (Ca,Pb)10(PO4,CO3) 6(OH,F,Cl)2.56.1.5H2O and CaCO3 dissolution with the formation of a PbCO3. The occurrence of this second mechanism improves the uptake efficiency but contribute to the increases of lead bioavailability because lead carbonate is more soluble than fluorpyromorphite. This fact could limit the use of PRs for remediation of contaminated soils and wastes. The Cu2+ and Cd2+ removal by PRs is controlled by adsorption mechanisms but dissolution /precipitation mechanisms also occur. In the case of Cu2+, fluorapatite dissolution followed by Cu2(PO4)(OH) precipitation. Neste trabalho, rochas fosfatadas brasileiras (PRs) foram usadas na imobilização de Pb2+, Cu2+ e Cd2+ de soluções aquosas. Concluímos que estes metais são principalmente imobilizados por fluorapatita, mas outros minerais tais com carbonatos de cálcio contribuem para esta imobilização. No caso do chumbo, dois mecanismos são propostos: a dissolução da Ca10(PO4)6F2 seguida pela precipitação de (Ca,Pb)10(PO4,CO3) 6(OH,F,Cl)2.56.1.5H2O e a dissolução de CaCO3 com formação de PbCO3. Este segundo mecanismo aumenta a eficiência do processo de remoção, mas contribui para tornar o chumbo mais biodisponível porque o carbonato de chumbo é mais solúvel que a fluorpiromorfita. Este fato pode limitar a utilização das rochas fosfatadas na regeneração de solos contaminados. A imobilização de Cu2+ e do Cd2+ pelas PRs é controlada por mecanismos de adsorção mas mecanismos de dissolução/precipitação também contribuem. No caso do Cu2+ a dissolução da fluorapatita é seguida pela precipitação da libetenita, Cu2(PO4)(OH).

In this work, the in vitro behavior of human osteoblast cells on the undulated surfaces of biphasic calcium phosphate tablets was investigated. The tablets were produced by uniaxial pressing with convex cylindrical undulations occupying only half of the surface area; the other half was flat. Chemical and physical characterization was performed by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). XRD and FTIR analyses revealed the presence of hydroxyapatite (HA) and alpha-tricalcium phosphate (alpha-TCP) in a well-defined ratio. Moreover, microtopography, evaluated by SEM and AFM, was similar on the flat region and on that with undulations. However, surface undulations induced different cellular arrangements, confirming the influence of the macrotopography on the cells orientation.

Isolated iron ions and iron oxide nanoparticles entrapped in alginate microspheres were studied by 57 Fe Mfssbauer spectroscopy (MS), electron paramagnetic resonance (EPR) and magnetization measurements. Ferric alginate beads were prepared by dropping sodium alginate solution into ferric chloride solution (0.1 and 0.5 M) with stirring under Ar atmosphere. MS and EPR spectroscopy show that iron is absorbed in alginate as Fe(III). The EPR suggests that isolated Fe(III) substitutes sodium in the polymeric structure (narrow line paramagnetic species at g=4.23). This mechanism induces the linking of the alginate units and the formation of the alginate microspheres. During this process, superparamagnetic iron hydroxide particles (broad line species at g=2.22) are precipitated inside the polymer network. MS measurements performed in diluted and concentrated Fe(III) samples displays a paramagnetic doublet at 300 K, and two components at 4.2 K due to a paramagnetic site and blocked superparamagnetic particles. D 2004 Published by Elsevier B.V.

Immobilization of toxic metals by calcium phosphates is a promising technology for treating contaminated soil, water and wastes. A detailed study on the mechanisms of lead immobilization by hydroxyapatite has been carried out using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). For this, synthetic hydroxyapatite powder were submitted to a sorption process through exposure to an aqueous solution containing 917 mg L−1 of lead for times that varied from 3 min to 54 h. The results obtained reinforce the hypothesis that hydroxypyromorphite formation is the end of a kinetic process in which the hydroxyapatite crystals are continuously dissolved and recrystallized in order to form more stable structures with higher lead content. Consequently, the use of calcium phosphates to immobilize lead ions seems to be technically viable.

Archaeological artefacts made of obsidian are all the more precious for archaeologists as they are witnesses of cultural, social or 'economic' relationships between prehistoric populations. The main obsidian sources reachable in these times have been identified and characterized by chemical analysis and fission track dating. Because of iron presence (from 1% to 10% expressed in Fe 2 O 3 ) it is possible to use Mossbauer spectroscopy and electron spin resonance (ESR) on geological samples to characterize different sources. We studied by electron spin resonance about seventy obsidians coming from six Mediterranean volcanic islands. The complex spectra are mainly due to iron in different states and site location (and sometimes isolated Mn 2+ ions). X-band (9 GHz) spectra exhibit a signal at g = 4.3 with a shoulder at 9.8 ascribed to isolated Fe 3+ in the glassy matrix with a rhombic environment (C 2y ). Condensed clusters of Fe 3+ ions give rise to a resonance line at g = 2.0 whose position and width do not depend on temperature and in addition to this signal broad resonance lines are ascribed to micro-crystallites of mixed iron oxides (hematite, magnetite and related spinels, titanates, silicates) as inclusions into the amorphous matrix of obsidian. When temperature decreases from 300 to 5 K these signals shift towards weak fields. The contribution of every signal to ESR spectrum is different from one source to the other according to the different thermodynamic conditions that occurred during obsidian formation. It is thus possible to discriminate a priori one geological source using ESR spectra. At room temperature the first differences appear at X-band, low temperatures experiments may allow to remove some ambiguities.

Porous hydroxyapatite (HA) has already been widely used as a bone substitute due to its similarity with the mineral part of the bone. In this work, cylindrical tablets with micro and macro porosity were produced from stoichiometric and deficient hydroxyapatites by using naphthalene as porosifier agent. The influence of the processing parameters such as Ca/P ratio of start material, calcination temperature, and naphthalene content on the characteristics of porous calcium phosphate tablets was evaluated. Three mineral phases-HA, alpha-TCP (alpha tri-calcium phosphate), and beta-TCP (beta tricalcium phos-phate)-with variable contents were identified by x-ray diffraction (XRD) and Fourier-transformed infrared spectroscopy (FT-IR). Image analysis and density measurements were used to characterize sample porosity. As expected, the total porosity of the calcinated material is not dependent on the stoichiometry of the precursor hydroxyapatite. For calcium-deficient hydroxyapatite, the increase in naphthalene content contributes to stabilize alpha-TCP phase, altering the relative phases content.

Calcium phosphate granules were produced through the calcination of three hydroxyapatites (HAs) at 1150 degrees C: nearly-stoichiometric (NS-HA), calcium-deficient (CD-HA), and carbonated (Carb-HA). The characterization using scanning electron microscope (SEM), X-ray diffraction (XRD), and Fourier-transformed infrared spectroscopy (FT-IR) showed that those granules exhibit strong differences in chemical composition, surface texture, and dissolution behavior. Sample dissolution in a simulated body fluid (SBF) and precipitation of a calcium phosphate layer on the granule surface were followed up for 7 days by chemical analysis of calcium content in SBF. After 80-min reaction, precipitation of new calcium phosphate phases predominates over the dissolution of original granules. Comparison between SEM images and XRD/FT-IR analysis revealed that the composition of the calcium phosphate layer and its precipitation rate depend on the HA composition and its heat treatment. Calcined carbonated apatite induces the precipitation of an octacalcium phosphate (OPC) layer, whereas a carbonated apatite layer is formed from calcined-deficient HA. The calcined nearly-stoichiometric HA exhibits low efficiency in producing carbonated apatite layer.

Geological sedimentary dolomite samples from the Superior Proterozoic are studied using electron paramagnetic resonance (EPR) spectroscopy. The complex spectra in the g=2.0 region is composed of Mn2+ lines and signals due to crystallization and radiation-induced defects. Measurements in microwave frequencies of 9.5 GHz (X-band) and 35 GHz (Q-band), and thermal and/or radiation treatments allowed identification of seven paramagnetic radicals in the g=2.0 region: (1) isotropic organic radical; (2) axial SO2 −; (3) axial PO2 0 or PO2 2−; (4) isotropic CO2 −; (5) axial CO2 −; (6) axial CO3 3−; (7) isotropic unknown line. The use of these paramagnetic centres as indicators of geological events is discussed.

The identification of geological sources of obsidians collected in archaeological sites provides important information about circulation routes and sociocultural relationships during prehistoric periods. This paper presents the preliminary results obtained by MS and EPR on geological obsidians from Ayacucho and Arequipa, in Peru and on archaeological obsidian artifacts from Cerrillos, an early Paracas site of the upper Ica valley, south of Lima (Peru).

The magnetization and anisotropy of Ni 81 Fe 19 /W 90 Ti 10 multilayers prepared by DC sputtering are presented. At high-angle X-ray diffraction, weak superlattice peaks appear around the NiFe (1 1 1) diffraction line, which indicate a fiber texture 〈1 1 1〉 for NiFe. The magnetization decreases with NiFe layer thickness t NiFe and the analysis of the results at 300 K indicates the presence of 6 A thick dead Ni 81 Fe 19 layer. The ferromagnetic resonance (FMR) spectra are obtained with the applied magnetic field parallel and perpendicular to the film plane at 300 K. Complicated spin-wave resonance spectra were observed and analyzed. From FMR, a negative value for Ni 81 Fe 19 /W 90 Ti 10 interface anisotropy is obtained.

The structural and magnetic properties of Fe/Zn films prepared by thermal evaporation have been studied by means of X-ray diffraction, vibrating-sample magnetometry and ferromagnetic resonance (FMR). For Fe layer thickness smaller than 20 A the saturation magnetization decreases with decreasing Fe thickness, which is an indication of the island growth of Zn and Fe–Zn interdiffusion at the layer interfaces. The effective field magnetization 4 πM eff of the Fe/Zn multilayers was determined from the FMR data in a rotating external magnetic field. The interface anisotropy constant of the Fe/Zn multilayers, K S , is found to be 1.0 erg/cm 2 at 300 K. This indicates the presence of a large perpendicular interface anisotropy and this may suggest that the largest part of K S originates from lattice misfit strain.