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Hybrid materials have been studied because in these materials the properties of organic components, such as elasticity and biodegradability, could be combined with the properties of inorganic components, such as good biological response, thereby transforming them into a single material with improved properties. In this work, Class I hybrid materials based on polyester-ureaurethanes and titania were obtained using the modified sol–gel method. This was corroborated using the FT-IR and Raman techniques which highlighted the formation of hydrogen bonds and the presence of Ti–OH groups in the hybrid materials. In addition, the mechanical and thermal properties and degradability were measured using techniques, such as Vickers hardness, TGA, DSC, and hydrolytic degradation; these properties could be tailored according to hybridization between both organic and inorganic components. The results show that Vickers hardness increased by 20% in hybrid materials as compared to polymers; also, the surface hydrophilicity increases in the hybrid materials, improving their cell viability. Furthermore, cytotoxicity in vitro test was carried out using osteoblast cells for intended biomedical applications and they showed non-cytotoxic behavior

In recent years, it has been verified that collective cell migration is a fundamental step in tumor spreading and metastatic processes. In this paper, we demonstrate for the first time how low-intensity ultrasound produces long-term inhibition of collective migration of epithelial cancer cells in wound healing processes. In particular, we show how pancreatic tumor cells, PANC-1, grown as monolayers in vitro respond to these waves at frequencies close to 1 MHz and low intensities (−2) for 48-72 hours of culture after ultrasound irradiation. This new strategy opens a new line of action to block the spread of malignant cells in cancer processes. Despite relevant spatial variations of the acoustic pressure amplitude induced in the assay, the cells behave as a whole, showing a collective dynamic response to acoustic performance, agreeing with the “cell jamming” effect defined before in the literature. Experiments carried out with samples without previous starving showed remarkable effects of the LICUs from the first hours of culture, more prominent than those with experiments with monolayers subjected to fasting prior to the experiments. This new strategy to control cell migration opens a new line of action in vivo to block the spread of malignant cells.

Degradable poly(ester urethane)s (PEUS)/nanosilica composites are prepared, and a preliminary evaluation of their potential to be used in calcified tissue regeneration is performed. First, poly(ethylene glycol succinate) (PEGS) of different molecular weights is prepared and then a prepolymer with an excess of 1,6-hexamethylene diisocyanate is synthesized; this prepolymer is subsequently extended with 1,4-butanediol in the presence of nanosilica particles. The effects of the structures of PEGS and PEUS are studied by means of attenuated total reflectance infrared, gel permeation chromatography, X-ray diffraction, thermogravimetric analysis, optical microscopy, and scanning electron microscopy. The materials show that similar crystalline structure independently of the molecular weight, however, increases the thermal resistance with higher molecular weight of nanocomposites. After soaking in simulated body fluid, the appearance of apatite phosphate bands in Fourier transformed infrared spectra suggests the bioactive character of these composites. In addition, degradation and toxicity test are performed. The materials are degradable but not cytotoxic after 7 days of testing.

Additive manufacturing (AM) techniques are becoming the approaches of choice for the construction of scaffolds in tissue engineering. However, the development of 3D printing in this field brings unique challenges, which must be accounted for in the design of experiments. The common printing process parameters must be considered as important factors in the design and quality of final 3D-printed products. In this work, we study the influence of some parameters in the design and fabrication of PCL scaffolds, such as the number and orientation of layers, but also others of &ldquo, hidden&rdquo, importance, such as the cooling down rate while printing, or the position of the starting point in each layer. These factors can have an important impact oin the final porosity and mechanical performance of the scaffolds. A pure polycaprolactone filament was used. Three different configurations were selected for the design of the internal structure of the scaffolds: a solid one with alternate layers (solid) (0&deg, 90&deg, ), a porous one with 30% infill and alternate layers (ALT) (0&deg, ) and a non-alternated configuration consisting in printing three piled layers before changing the orientation (n-ALT) (0&deg, 0&deg, ). The nozzle temperature was set to 172 &deg, C for printing and the build plate to 40 &deg, C. Strand diameters of 361 &plusmn, 26 &micro, m for room temperature cooling down and of 290 &plusmn, 30 &micro, m for forced cooling down, were obtained. A compression elastic modulus of 2.12 &plusmn, 0.31 MPa for n-ALT and 8.58 &plusmn, 0.14 MPa for ALT scaffolds were obtained. The cooling down rate has been observed as an important parameter for the final characteristics of the scaffold.

HA-based hybrid hydrogels were successfully developed. The polysaccharide (HA) chains were chemically modified and hybridized via amidation of their carboxylic groups with aminosilane molecules. HA-polysaccharide chains were crosslinked by a 3D siloxane organic-inorganic matrix via sol-gel. The novel inorganic crosslinking network (PDMS-SiO2) provided to sodium hyaluronate (HA) strong chemical bonds, giving restriction to their natural hydrophilicity and stiffness to its structure (improved rheological properties). It was observed that synthesis conditions such as starting HA concentration solution and temperature determined gelling times, efficiency in the polysaccharide chemical modification and in crosslinking hydrolysis-condensation reactions, resulting in the siloxane organic-inorganic matrix. Drying processes influenced crosslinking in HA hybrid hydrogels, either by enhancing polycondensation reactions or inhibiting them. Room temperature-drying produced more densified hybrid structures. Freeze-drying increased porosity and surface hydroxyl groups (-OH) resulting in more Q3 structural units. 60 °C-drying boosted polycondensation of monodendate structural units, enhancing the formation of hybrid D-Q bonds.

Hydroxyapatite is a bioactive ceramic frequently used for bone engineering/replacement. One of the parameters that influence the biological response to implanted materials is the conformation of the first adsorbed protein layer. In this work, the adsorption and conformational changes of two fibroid serum proteins; fibronectin and fibrinogen adsorbed onto four different hydroxyapatite powders are studied with a Quartz Crystal Microbalance with Dissipation (QCM-D). Each of the calcined apatites adsorbs less protein than their corresponding synthesized samples. Adsorption on synthesized samples yields always an extended conformation whereas a reorganization of the layer is observed for the calcined samples. Fg acquires a "Side on" conformation in all the samples at the beginning of the experiment except for one of the synthesized samples where an "End-on" conformation is obtained during the whole experiment. The Extended conformation is the active conformation for Fn. This conformation is favored by apatites with large specific surface area (SSA) and on highly concentrated media. Apatite surface features should be considered in the selection or design of materials for bone regeneration, since it is possible to control the conformation mode of attachment of Fn and Fg by an appropriate selection of them. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2585-2594, 2016.

Adenocarcinoma of the pancreas (PDAC) accounts for 2.4% of all cancers diagnosed and is the fourth leading cause of cancer death, with almost equal rates of incidence and mortality [1]. By 2030, pancreatic cancer is projected to be the second leading cause of cancer-related death [2], surpassing breast, prostate and colorectal cancer. The overall survival at 5 years of around 7.2% as the majority of patients present with advanced disease at diagnosis. Patients with localized disease are treated with surgery, with or without neoadjuvant chemotherapy/ radiotherapy, followed by adjuvant chemotherapy. The majority (around 80%) of patients are treated only with chemotherapy as they have an advanced disease. Patients are treated in the first line with gemcitabine-abraxane or Folfirinox and with Naliri plus 5FU in the second line. There have been few clinical advances in PDAC treatment over the last 20 years and chemotherapy is the only treatment option available for the majority of patients. These tumours are also resistant to many targeted therapies such as anti-EGFR therapy like cetuximab [3] due to the presence of a KRAS mutation in the majority of primary tumors. Personalized medicine strategies have not yet been established in pancreatic cancer as in other more common tumour types. Thus, novel anti-tumour strategies are an important clinical need in order to improve survival rates., AEI/FEDER, UE DPI 2017-90147-R., Intramural call for new research projects for clinical researchers and emerging research groups. IRYCIS. (2018/0240), Iberoamerican Network CYTED-DITECROD-218RT0545.

Osteoproductive materials that induce quick bone regeneration are needed for the developing area of scaffold-based bone engineering. Bioactive silica-based glasses, ceramics, and hybrids are called to play an important role in this field. Organic–inorganic hybrid materials based on SiO2-modified PDMS–P2O5–CaO are studied in this work. These materials are synthesized by the sol–gel method, and the influence of the composition on the reaction kinetic, obtained porosities, degradation and bioactive behavior, and cytotoxicity is studied. Materials with greater contents in CaO yield faster reaction kinetics and produce porous materials that favor a quicker degradation, whereas with greater P2O5 contents produce denser and more stable materials. The incorporation of CaO and P2O5 up to 5 and 25 % in weight into the SiO2 network, respectively, resulted in an increase of the apatite-forming ability in PBS. None of the studied compositions are cytotoxic, showing cellular viability over 70 % at all times.

Compounds having the general formula MFO·4H2O where M = Ca or Sr and FO = a folate anion were prepared and their structure and physico-chemical properties were determined by elemental and thermal TGA, DSC analysis, FTIR, and EDAX spectroscopies and DRX. The results indicate that the two compounds form stable structures where folic acid acts as a self-bridging ligand via two bidentate carboxylate groups. Moreover the two compounds showed a low toxicity in vitro response as h-osteoblast cell viability was not negatively affected by the presence of folate derivatives within the range of 0.063-0.5 mg ml-1. The results also indicate that the folate derivatives that are formed overcome the toxic effects related to free Sr2+ ions. The range of maximum cell viability corresponding with a concentration of SrFO falls within the in vitro physiologically active range for strontium while within the same range the strontium derivative showed a potential osteogenic activity as indicated by the overexpression of ALP activity.

Emulsion-templated (polyHIPE) scaffolds for bone tissue engineering were produced by photopolymerisation of a mixture of trimethylolpropane tris(3-mercaptopropionate) and dipentaerythritol penta-/hexaacrylate in the presence of hydroxyapatite (HA) or strontium-modified hydroxyapatite (SrHA) nanoparticles. Porous and permeable polyHIPE materials were produced regardless of the type or incorporation level of the bioceramic, although higher loadings resulted in a larger average pore diameter. Inclusion of HA and SrHA into the scaffolds was confirmed by EDX-SEM, FTIR and XPS and quantified by thermogravimetry. Addition of HA to polyHIPE scaffolds significantly enhanced compressive strength (148–216 kPa) without affecting compressive modulus (2.34–2.58 MPa). The resulting materials were evaluated in vitro as scaffolds for the 3D culture of MG63 osteoblastic cells vs. a commercial 3D cell culture scaffold (Alvetex®). Cells were able to migrate throughout all scaffolds, achieving a high density by the end of the culture period (21 days). The presence of HA and in particular SrHA gave greatly enhanced cell proliferation, as determined by staining of histological sections and total protein assay (Bradford). Furthermore, Von Kossa and Alizarin Red staining demonstrated significant mineralisation from inclusion of bioceramics, even at the earliest time point (day 7). Production of alkaline phosphatase (ALP), an early osteogenic marker, was used to investigate the influence of HA and SrHA on cell function. ALP levels were significantly reduced on HA- and SrHA-modified scaffolds by day 7, which agrees with the observed early onset of mineralisation in the presence of the bioceramics. The presented data support our conclusions that HA and SrHA enhance osteoblastic cell proliferation on polyHIPE scaffolds and promote early mineralisation.

The preparation of apatite–alendronate hybrid materials by reactive milling is proposed in this work. Calcium phosphate compounds of various compositions have been associated to bisphosphonates and found suitable for local application with release kinetics of the drug compatible with the inhibition of bone resorption. Hybrid compounds have been obtained by reactive milling. The compositions used were: AP(X-100), Alendronate(X) where X=7 and X=15. An interaction between the hydroxyl group of the apatite and the amine group of alendronate can be identified with FTIR and enables to confirm the formation of the hybrids. The incorporation of the alendronate hinders the growing of the apatite crystals resulting in smaller coherent domains of diffraction for the apatite phase.

Protein-surface interaction may determine the success or failure of an implanted device. Not much attention have been paid to the specific surface parametes of hydroxyapatite (OHAp) that modulates and determines the formation and potential activity of the layer of proteins that is first formed when the material get in contact with the host tissue. the influence of specific surface area (SSA), crystallite size (CS) and particle size (PS) of OHAp on the adsorption of proteins relevant for bone regeneration is evaluated in this article. OHAp have been prepared by a wet chemical reaction of Ca(OH)(2) with H(3) PO(4) . One set of reactions included poly acrylic acid in the reactant solution to modify the properties of the powder. Fibrinogen (Fg) Fraction I, type I: from Human plasma, (67% Protein), and Fibronectin (Fn) from Human plasma were selected to perform the adsorption experiments. The analysis of protein adsorption was carried out by UV/Vis spectrometry. A lower SSA and a different aspect ratio are obtained when the acrylic acid is included in the reaction badge. The deconvolution of the amide I band on the Raman spectra of free and adsorbed proteins reveals that the interaction apatite-protein happens through the carboxylate groups of the proteins. The combined analysis of CS, SSA and PS should be considered on the design of OHAp materials intended to interact with proteins.

Introduction The gradual aging of the population results in increased incidence of osteoporotic bone fractures. In a good quality bone, the fixation with the usual methods is adequate, but not in osteoporotic bone, in which consolidation delays and other complications are common, with failure rates for screws up to 25%. Objective To test fibronectin loaded hydroxyapatite as a complementary treatment for osteoporotic fractures. Material and Methods This study was performed in a vivo model; 42 female osteoporotic adult rabbits 4–5 kg (White New Zealand) were used. Two groups (hydroxyapatite and fibronectin loaded hydroxyapatite) and a control group were tested. 3 time points 24 h, 48 h and 5 days were studied. Defects were created in both femurs, in one of them, a cannulated screw (4 mm) and a biocompatible material were placed; in the other femur a screw was inserted without supplemented material forming the control group. Osteoporosis was induced from models already known throughout administration of steroids. Samples were analyzed histologically and through imaging (micro Ct). Results Basal levels of BMD are observed below to normal when compared to other studies (0.25/0.3 instead of 0.4). Global and dependent of time analysis of samples, show no significant differences for samples analyzed. However, an important trend was noted for variables that define the trabecular bone microarchitecture. Indices that define trabecular microarchitecture in the comparative analysis found to have statistical differences ( p Discussion Osteosynthesis in an osteoporotic bone is a challenge for the surgeon, due to a reduced bone mineral density and different bone architecture. The main finding was the verification of the hypothesis that the trabecular bone parameters increases with our augmentation material in weak rabbit bone quality. Also, the histological analyses of samples show an increase of non inflammatory cells in protein samples (OHAp-Fn) from the first 24 hours. Conclusion An early response of rabbit osteroporotic bone to a complementary treatment with fibronectin loaded hydroxyapatite has been observed. This response is reflected in greater values for indices that define the trabecular bone microarchitecture, thickness and separation, a greater non-inflammatory cellularity after only 24 hours and an increased amount of connective tissue observed at 48 hours.

Titanium compounds have demonstrated great interfacial properties with biological tissues whereas a wide variety of polyurethanes have also been successfully probed in medical applications. However, studies about hybrids based on polyurethanes/TiO

The purpose of the current study was to investigate whether the cryopolymerization technique is capable of producing suitable scaffolds for bone tissue engineering. Cryopolymers made of 2-hydroxyethyl methacrylate and acrylic acid with (W1 and W20) and without (W0) wollastonite particles were prepared. The elastic modulus of the specimens rose one order of magnitude from W1 to W20. Total porosity reached 56% for W0, 72% for W1 and 36% for W20, with pore sizes of up to 2 mm, large interconnection sizes of up to 1 mm and small interconnection sizes of 50-80 µm on dry specimens. Cryogels swell up to 224 ± 17% for W0, 315 ± 18% for W1 and 231 ± 27% for W20 specimens, while maintaining the integrity of the bodies. Pore sizes > 5 mm can be observed for swollen specimens. The biocompatibility of the samples was tested using human mesenchymal stem cells isolated from bone marrow and adipose tissues. Both types of cells attached and grew on the three tested substrates, colonized their inner regions and organized an extracellular cell matrix. Fibronectin and osteopontin levels decreased in the media from cells cultured on W20 samples, likely due to increased binding on the ECM deposited by cells. The osteoprotegerin-to-receptor activator of nuclear factor-κB ligand secretion ratios increased with increasing wollastonite content. Altogether, these results indicate that an appropriate balance of surface properties and structure that favours stromal cell colonization in the porous cryogels can be achieved by modulating the amount of wollastonite.

Though hydroxyapatite has the ability to promote bone growing, devices based on OHAp are mechanically weak and need to be reinforced for load bearing applications or in the manufacturing of scaffolds for bone regeneration. Graphite (Gr) could provide appropriate reinforcement properties to OHAp without being deleterious for the biocompatibility of the system. This paper describes an accelerated synthesis of the OHAp with ultrasonic agitation in the presence of functionalized graphite (GO). The toxicity of the Graphite and the GO-OHAp system is evaluated. GO-OHAp was produced by a wet chemical reaction involving CaCl2 and Na2HPO4. The calcium salt solution was added first and the solution sonicated for 1 hour, before repeating the operation with the phosphate solution. Biocompatibility was tested by using a primary cell culture of HOB (ECCAC). The disappearance of the maximum at 2q = 26.32º corresponding to the d002 plane of graphite and the appearance of the maximum at 2q = 13.2º in the XRD patterns is related with an expansion of the grapheme sheets from 0.34 nm to 0.59 nm and it has been used to assess the graphite oxidation. The OHAP on GO growing has been confirmed by the appearance of a broad peak centred at 2q = 31.5º and a sharpened peak at 2q = 26.0º characteristic of low crystalline apatites. Although the employed graphite can be considered biocompatible, cellular viability is significantly improved by the presence of apatite.

This paper focuses on the preparation of siloxane-polyurethane hybrid materials using a sol-gel method. The global aim of the project is to tailor mechanical properties, degradability rate, bioactivity and biocompatibility to design scaffolds for musculoskeletal applications. A series of seven hybrid materials were synthesized with varying the proportion of polydimethylsiloxane (PDMS), and Polyurethane (PU). The organic part ratios (by weight) employed were (% PDMS:% PU) 30:0, 35:5, 20:10, 15:15, 10:20, 5:25, and 0:30. The organic part was reacted with constant 70 % TEOS to obtain the hybrid materials. A sol-gel process was selected for the synthesis of the hybrids. The characterization of materials was carried out by the fourier-infrared spectroscopy (FT-IR), x-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electronic microscopy (SEM) and proton nuclear magnetic resonance (1H-NMR) techniques in order to analyze the structure, microstructure and chemical composition of the hybrid materials. Gelification time depends on the proportion of PU used. When no PU is employed, the gel time is 8 hours but it rises up to 18 days for 30 % of polyurethane. Materials range from opaque to translucent but with a greater fragility for greater amounts of polyurethane. No differences in the bonding of materials could be appreciated.

The manufacturing of a composite made of a synthetic bioactive ceramic, pseudowollastonite (psW), and a bioresorbable copolymer ethylmethacrylate–vinylpyrrolidone (EMA/VP) is presented in this article. psW porous blocks were produced by dipping an open porous polyurethane foam in a psW containing slurry. A 40/60 wt % EMA/VP monomers mixture was poured on the blocks, and free radical polymerization initiated by azobis(isobutyronitrile) at 50°C. Disks of 1 mm height were obtained by cutting the composite with a diamond saw, and bioresorption and bioactivity of the specimens were tested by immersion of the disks into SBF. A ceramic/polymer weight ratio of 72/28, greater than the usually achievable ratio by polymeric solidification of slurries of monomers charged with a powdered solid component, has been obtained. The system is bioactive and does not change the pH of the medium during the degradation test. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res 80A:, 2007

Bisphosphonates (BPs) may play an important role in minimizing osteolysis. In this work two new bisphosphonates pertaining to second and third generations respectively, have been synthesized and incorporated onto a chemically enriched hydroxyapatite. BP synthesis has been performed by adding H3PO3, PCl3 and methanesulfonic acid over 4-aminophenyl acetic acid (APBP) and 1-H-indole-3-acetic acid (IBP) respectively at 65°C in a N2 atmosphere. These compounds bear a primary amine group bonded to an aromatic ring, and a secondary amine group within a heterocyclic ring respectively. A chemically enriched hydroxyapatite with a chemical content corresponding to a 50% fluorided hydroxyapatite has been synthesized. Ceramic bodies manufactured by uniaxial pressure followed by cold isostatic press have a 97% density and submicron grain size. The BP was adsorbed onto the surface by immersion in a stirred solution at 37°C for 48 hours. A 10-fold decrease of the surface energy was observed for bodies modified with the APBP whereas only a 25 % decrease is obtained for bodies loaded with the bisphosphonate loaded with the IBP.

Iron is a vital element of cellular function within the body. High concentrations of iron can be found in the kidneys and the circulatory system. In bones and teeth it is present as a trace element. The use of iron-based compounds in combination with hydroxyapatite offers a new alternative for prosthetic devices. This work investigates the synthesis and processing of iron containing apatites as a possible new type of ceramic for biomedical devices. Stoichiometric and calcium deficient iron containing apatites were synthesized by a wet chemical reaction with di-ammonium-hydrogen-phosphate, calcium nitrate and a ferrous iron nitrate solution. A secondary phase of tri-calcium-phosphate (TCP) was observed after heat treatment of iron containing, calcium deficient, hydroxyapatite. The apatite structure was maintained after heat treatment of stoichiometric apatite, synthesized in the presence of iron. Sintering in air produced oxidation of Fe2+ to Fe3+, resulting in the formation of hematite as a secondary phase. The introduction of iron into the synthesis of hydroxyapatite causes: (i) an increase of the a-lattice parameter after synthesis and heat treatment in air; (ii) an increase in the c-lattice parameter after sintering in air.

The development of synthetic apatites that replicate the features and properties of the contained in natural tissues will help to diminish the misfit between artificial implants and natural hostesses but the structure of these compounds is still under discussion. The variability in Ca/P ratio of calcium deficient apatites has been explained through different models: surface adsorption, lattice substitution and intercrystalline mixtures of hydroxyapatite and octacalcium phosphate. This work investigates which of the models mentioned suits better in a range of samples. Hydroxyapatites obtained by precipitation, by hydrolysis of dicalcium phosphate and calcined samples with Ca/P ratio between 1.50 and 1.77 and specific surface area between 7 and 108 m2/g have been analysed. OCP and surface adsorption models suit better for great SSA particles and low Ca/P ratio while for smaller SSA particles the lattice substitution model is more accurate. SSA also plays the main role when the capacity to absorb substances is studied though their chemistry can not be explained solely in terms of surface reactivity.

Nine samples of Ca-deficient apatite (Ca-def Ap) were prepared from suspensions of CaHPO4 (monetite) at 90 degrees C by raising the pH from approximately 4 through release of NH3 produced by the hydrolysis of urea. Products were dried at 100 degrees C for 24h and studied by chemical analyses, X-ray powder diffraction (XRPD) (and Rietveld analysis of this data), Ca/P ratio determination (quantitative phase analysis of samples after heating to 900 degrees C from Rietveld analysis of XRPD data), scanning electron microscopy, He pycknometry, 1H and 31P MAS NMR spectrometry and Fourier transform infrared and Raman spectroscopy. All samples contained apatite, but three also contained monetite. Infrared and Raman spectroscopy confirmed the presence of HPO4(2-) and absence of carbonate ions in the six monetite-free samples. Mean results for the six samples were: a = 9.4320(40), c = 6.8751(31) A; unit cell formula from chemical analysis neglecting protonation of phosphate ion, Ca(9.303(50))(PO4)6(OH)(0.606(99)).1.97(12)H2O; theoretical density 3.10 g cm(-3); experimental density (mean for three samples) 3.15 g cm(-3); and Ca/P mole ratio from chemical analysis and phase analysis after heating to 900 degrees C, 1.550(8) and 1.550(2), respectively. An earlier assignment of a line at 6 ppm in the 1H NMR spectrum of similar samples to HPO4(2-) ions could not be confirmed; hence no information about the HPO4(2-) ion content could be derived, in disagreement with the previous NMR study. A shoulder at approximately 0.9 ppm relative to 85 wt% H3PO4 in the 31P NMR spectrum was assigned to HPO4(2-) ions. Occupancies from the Rietveld structure refinements indicated preferential loss of Ca from Ca2 sites compared with Ca1, but the loss was substantially smaller than expected from chemical analyses. It is suggested that imperfect modelling of the structure in the refinement, particularly disorder associated with the Ca2 site, resulted in errors in Ca2 occupancies. The P-O bonds were slightly shorter than those in stoichiometric hydroxyapatite, rather than longer as might be expected from protonation of phosphate tetrahedra. However, consideration of known acid phosphate structures indicated that it was unlikely that the increase in P-O lengths would be sufficient to be detected. The observed decrease was tentatively assigned to the presence of Ca2+ ion vacancies.

Hydroxyapatite has been frequently described as an osteoconductive but not osteoinductive material based on failure to observe bone formation in nonbony sites. Bisphosphonates (BPs) are stable pyrophosphate analogs, that enhance the proliferation, differentiation and bone forming activity of osteoblasts and are potent inhibitors of bone resorption. In this paper, the modification of a calcium hydroxyfluor carbonate apatite with sodium alendronate and (4-(aminomethyl)benzene)bisphosphonic acid is described. The surface modification is carried out by refluxing the apatite in a bisphosphonate acetone solution. Modified particles are characterized by thermal analysis, ATR-IR spectroscopy and contact angle between other techniques. A weight loss between 150 and 500ºC can be observed for the modified apatites. IR spectra show the appearance of bisphosphonate bands on modified powders. The surface energy of the modified apatite is reduced up to a 74% from the total apatite value after the alendronate surface modification with a decrease of 58% of the polar component main responsible of the cellular interaction of biomaterials., Financial support through research project MAT2002-04147-C02-02, CICYT (Spain) is acknowledged. LMRL has been supported by CAM regional government (Spain) through the program to incorporate doctors to the Madrid research system.

Modification of hydroxyapatite surfaces can improve the properties of biomedical devices. The objective of this work was to encapsulate hydroxyapatite particles with a fluorapatite layer. A suspension of hydroxyapatite microspheres was prepared in a solution at different pH and treated with ammonium fluoride. pH, calcium, and fluoride were monitored in real time and particles subjected to fluoride analysis. After addition of fluoride, it was found that more material is released from the particle surface at low pH conditions, but leads to a high fluoride uptake from solution. Low solution fluoride levels produce a fluorapatite layer, but higher fluoride levels produce calcium fluoride.

Hydroxyapatite (OHAp) particles with a specific surface area of 9 m2/g were obtained through a thermal treatment at 900 °C followed by deagglomeration by ball milling in ethanol for 20 h. Slurries with a 50-vol.% solids loading were prepared by mixing the particles with water. Organic inclusions with particles sizes from 55 to 750 μm were added and ceramic bodies were consolidated by slip casting. Dense and porous ceramic bodies were obtained with densities as low as 30% and as high as 94% and pore sizes up to 750 μm. The possibility of manufacturing ceramic bodies with porosity gradients designed according to the features of the porous ceramic bodies was studied in order to adapt them to the severe requirements of tissue engineering scaffolds.

Hydroxy-fluorapatites (OH-FAps) occur biologically in teeth and form the basis for application as biomaterials. This work aims to synthesize a series of fluoride substituted calcium hydroxyapatites (OHAps) to determine how fluoride influences the synthesis and the resulting characteristics of solid solutions. OH-FAPs powders were synthesized with a chemical composition of Ca(10)(PO(4))(6)(OH)(2-x) F(x), with x=0.0, 0.4, 0.8, 1.2, 1.6 and 2.0. The synthesis of partially substituted OHAp yields materials with lower crystallinity and higher specific surface area than OHAp or fluorapatite (FAp). The smallest crystal size of 263A, occurs at less than 50% hydroxyl substitution with fluoride at x=0.4, and the highest surface area of 132m(2)/g occurs at x=0.8. Reaction kinetics occur faster at higher fluoride content, producing the expected Ca/P ratio of 1.67 only for x=2.0. X-ray and IR studies show that OH-FAPs are homogeneous solid solutions instead of mixtures of OHAp and FAp. The presence of a high fluoride concentration increases the driving force for crystal growth during the calcination process.

X-ray diffraction (XRD) patterns of hydroxyfluorapatites with a nominal composition of Ca10(PO4)6(OH)2-xFx, where x = 0.0, 0.4, 0.8, 1.2, 1.6, and 2.0, were collected and analyzed using the Rietveld method. A multiphase Rietveld analysis performed on calcined samples reveals a range of Ca/P ratios from 1.56 for the sample with x = 0.4 to 1.67 for the sample with x = 2.0 on the synthesized powders. Calcined apatites exhibit a decrease in the lattice parameter a, a greater crystallite size, lower distortion in the phosphate tetrahedra, and greater stability of the apatite structure for higher fluoride contents.

The layering of fluorapatite on hydroxyapatite bodies provides a means of decreasing the solubility of hydroxyapatite, providing fluoride for possible stimulation of bone formation and delaying the release of calcium and phosphate from the more soluble hydroxyapatite. The purpose of this work was to encapsulate hydroxyapatite particles with fluorapatite spanning a thickness more than several crystallites deep. A three-step procedure was employed. Hydroxyapatite powder was immersed in an electrolyte solution until an equilibrium was established between the solid and the dissolved calcium at pH 4.67 and 37 °C. Equilibrium was determined by measurement of dissolved calcium with a calcium-specific ion-specific electrode. A 5×10−2 M ammonium fluoride added to the suspension resulted in a rapid decrease of both calcium and fluoride in the solution. Analysis with X-ray diffraction indicated that a fluoride rich layer containing calcium fluoride deposited onto the particle surface. Scanning electron microscopy revealed submicron spherical precipitate clusters on the hydroxyapatite particles. These clusters transformed to fluorapatite by soaking in a 0.1 M K2HPO4 solution at pH 8 and 70 °C. A total time of 10 h was necessary for complete transformation of CaF_2 into fluorapatite.

The transformation of calcium sulfate hemihydrate into gypsum via reaction with water has been used for many years to produce materials for bone augmentation. In this work, a mixture of CaSO4·1/2H2O and hydroxyapatite was prepared, and its behavior as cement was studied and compared with that of pure calcium sulfate hemihydrate. The setting process was monitored with Gillmore needles, X-ray diffraction, and differential scanning calorimetry. The utilization of the mixture allows one to prepare homogeneous pastes with better manipulation characteristics than pure calcium sulfate hemihydrate. The workability and setting time of the hydroxyapatite-containing cements are higher than those of pure CaSO4·1/2H2O. The different techniques employed allow us to relate the initial setting time with the chemical transformation of the calcium sulfate hemihydrate into calcium sulfate dihydrate. The biphasic specimens show an improved bioactivity response compared to pure hydroxyapatite or gypsum when soaked in a simula...

Hydroxyapatite/solgel glass biphasic material has been obtained in order to improve the bioactivity of the hydroxyapatite (OHAp). A mixture of stoichiometric OHAp and the precursor gel of a solgel glass, with nominal composition in mol% CaO-26, SiO2-70, P205-4, has been prepared. The amounts of components used have been selected to obtain a final relationship for OHAp/solgel glass of 60/40 on heating. Two different thermal treatments have been used: (i) 700 degrees C, temperature of solgel glass stabilisation and (ii) 1000 degrees C, lower temperature of hydroxyapatite sintering. The bioactivity of the resulting materials has been examined in vitro by immersion in simulated body fluid at 37 degrees C. The results obtained show that both materials are bioactive. The apatite-like layer grown is greater for the new materials than for the OHAp and the solgel glass themselves.

The aims of this paper are: (1) to review the current state of the art in the field of cartilage substitution and regeneration; (2) to examine the patented biomaterials being used in preclinical and clinical stages; (3) to explore the potential of polymeric hydrogels for these applications and the reasons that hinder their clinical success. The studies about hydrogels used as potential biomaterials selected for this review are divided into the two major trends in tissue engineering: (1) the use of cell-free biomaterials; and (2) the use of cell seeded biomaterials. Preparation techniques and resulting hydrogel properties are also reviewed. More recent proposals, based on the combination of different polymers and the hybridization process to improve the properties of these materials, are also reviewed. The combination of elements such as scaffolds (cellular solids), matrices (hydrogel-based), growth factors and mechanical stimuli is needed to optimize properties of the required materials in order to facilitate tissue formation, cartilage regeneration and final clinical application. Polymer combinations and hybrids are the most promising materials for this application. Hybrid scaffolds may maximize cell growth and local tissue integration by forming cartilage-like tissue with biomimetic features, This work was supported by SIP-IPN 20170510 Project (Mexico), DGICYT Project, MAT2014-51918-C2-I-R (Spain), (CONACYT/CSIC)-EMHE program through project No. MHE200011 (Mexico-Spain). DA Sánchez-Téllez also acknowledges CONACYT (Mexico) for the scholarship given. The authors acknowledge Stephanie Cisneros-Téllez for helping them in the digitalization of Figures 1, 4 and 8.

A perfect control on the final ceramic features will enable the research/clinical community to spread the use of calcium phosphate ceramic bodies to a large number of applications and/or requirements. The mechanical properties of hydroxyapatite ceramic bodies manufactured by different techniques and with different porosities is presented. The flexural strength, hardness, fracture toughness, surface roughness, and their evolution after immersion in SBF are studied. An increase of the mechanical properties with density is observed. The factors governing these results are analyzed. The increase of the porosity percentage of the bodies results in an increase on the surface roughness. The degradation studies show that the HA ceramics keep their integrity and mechanical properties under physiological conditions during the soaking time studied. The OHAp ceramic bodies with controlled porosity could be appropriated for hard tissue substitution or as a carriers for controlled delivery of drugs or as scaffolds for tissue engineering.

Reliable bioceramics are needed to implement the high requirements that living tissues demand. This work focuses on the processing steps necessary to manufacture advanced ceramics that can be used as implant devices. The influence of the heat treatment temperature on the characteristics of a precipitated hydroxyapatite (OHAp) powder was evaluated in order to obtain an appropriate specific surface area for colloidal processing. Ball milling of the calcined powders for 20 h was required to improve the rheological properties of the suspensions and the packing ability during consolidation. Different dispersing agents were tested and the first trial was made based on their effect on the zeta potential. The most promising ones were then selected and their efficiency was evaluated from rheological measurements and slip-casting performance of suspensions prepared at different solids loading. Targon 1128 was revealed to be the most efficient dispersant, enabling to prepare fluid suspensions containing 50 vol% solids and the highest green and sintered density values to be obtained.

The growing necessity of biomaterials has increased the interest in calcium phosphates, particularly apatites. Small differences in stoichiometry, crystallinity, morphology, etc. could contribute to the different clinical behaviors observed, so perfect control of the synthesis parameters and their influence in the characteristics of the samples is a must. In the present work, a crystallization set able to produce massive and reproducible quantities of different calcium phosphates is presented. Apatites with different stoichiometries and morphologies are prepared, and the effects of varying synthesis conditions are analyzed. Temperatures in the range 25−37 °C are necessary to obtain apatites with crystal sizes in the range of adult human bone. Longer reaction times produce increased Ca/P ratios. Aging of the precipitated powder can lead to the incorporation of minor quantities of carbonate. It is possible to force the incorporation of carbonate ions into the apatitic structure without introducing monovalen...

Pechini method is a materials synthesis method based on the preparation of a polymeric matrix. The advantage of this method is the ability to obtain materials with different particle sizes depending on the synthesis condition with a homogeneous distribution. In this work, carbonated hydroxyapatite (c-OHAp) nanoparticles were obtained by a modified Pechini method. To obtain the polymeric precursor of the c-OHAp, the polymeric matrix was prepared through a polyesterification reaction between citric acid and ethylene-glycol. Adding calcium hydroxide and ortophosphoric acid in aqueous solutions, raising the temperature up to 140 C/2 h and keeping constant the pH at 8. The polymeric matrix was calcinated at different ranges of temperature from 200 to 600 C in order to obtain the c-OHAp powder. The results show the presence of c-OHAp a as unique phase. The thermal analysis indicates that the c-OHAp phase was obtained at 600 C. The particle size of the obtained material was\50 nm

Composite biomaterials with good mechanical response and a partially biodegradable character were prepared by the free radical polymerization of mixtures of α-Al 2 O 3 , low-molecular-weight but crystalline poly(L-lactic acid) (PLLA), and methyl methacrylate (MMA). Cylindrical specimens prepared with different composition were characterized by thermogravimetry, calorimetry, 1 H-NMR spectroscopy, and x-ray diffraction (XRD). The in vitro biodegradative process was studied in different media, following variations of the pH, gravimetric weight loss of the specimens, and crystalline domain change by XRD after immersion in pure water and buffered solutions at pH 4.0 and pH 8.0 for 90 days. Formation of a relatively porous structure with good cohesion after the biodegradative treatment (confirmed by SEM) was observed. These systems can be considered for applications in orthopedic surgery as filling biomaterials and even as control drug-delivery systems.

The purpose of this work is to evaluate how the surface modification of apatites with alendronate may affect the adsorption of proteins relevant for bone regeneration. Two different apatites were synthesized for the study. Both of the powders were obtained by co-precipitation, assisted either by mechanical or by ultrasonic stirring. Hydroxyapatite-alendronate hybrid compounds were obtained by reactive milling and the protein adsorption experiments were done by mixing 10 mg of the hydroxyapatites and hybrids powders with 1.5 mL of a 0.1 mg/mL fibronectin solution. After 24h of digestion and separation of the solid from the liquid, the protein remaining in the liquid was measured by UV/VIS Spectrometry. The formation of the hybrids has been confirmed by the shift of significant Raman bands assigned to νP-O(H) and δP-OH bands that indicates changes in the P-O bond of the alendronate due to different modes of coordination to the Ca2+ ion of the apatite. Hybrids materials adsorb less fibronectin than their corresponding hydroxyapatite precursors.

Composite materials are very promising biomaterials for hard tissue augmentation. The approach assayed in this work involves the manufacturing of a composite made of a bioactive ceramic, natural wollastonite (W) and a nanostructured copolymer of ethylmethacrylate (EMA) and vinylpyrrolidone (VP) to yield a bioresorbable and biocompatible VP–EMA copolymer. A bulk polymerization was induced thermally at 508C, using 1 wt % azobis(isobutyronitrile) (AIBN) as free-radical initiator. Structural characterization, compressive strength, flexural strength (FS), degradation, bioactivity, and biocompatibility were evaluated in specimens with a 60/40 VP/EMA ratio and ceramic content in the range 0–60%. A good integration between phases was achieved. Greater compression and FS, in comparison with the pure copolymer specimens was obtained only when the ceramic load got up to 60% of the total weight. The soaking in NaCl solution resulted in the initial swelling of the specimens tested. The maximum swelling was reached after 2–3 h of immersion and it was significantly greater for lower ceramic loads. This result makes the polymer component the main responsible for the interactions with the media. After soaking in SBF, microdomains segregation can be observed in the polymer component that can be related with a dramatic difference in the reactivity of both monomers in free radical polymerization, whereas the formation of an apatite-like layer on the W surfaces can be observed. Biocompatibility in vitro studies showed the absence of cytotoxicity of all formulations. The cells were able to adhere on the polystyrene negative control and on specimens containing 60 wt % wollastonite forming a monolayer and showing a normal morphology. However, a low cellular growth was observed. 2008 Wiley Periodicals, Inc. J Biomed Mater Res 88A: 53–64, 2009

Bisphosphonates (BP) are drugs currently administered orally to treat diseases characterised by an excessive bone resorption. Alternative and more efficient delivery routes and more potent compounds are being investigated. Three implantable delivery systems, which allow the controlled release of therapeutic agents from the device core, are examined in this paper. (4- (aminomethyl) benzene) bisphosphonic acid (ABBP) was incorporated on Ca8.8Na0.8(PO4)4.8(CO3)1.2(OH)0.4F1.6 particles by refluxing the powder in a 60 mmol suspension in acetone at 60ºC for 5 hours. 4-aminophenyl acetic bisphosphonate monosodium salt (APBP) and 1- H-indole-3-acetic bisphosphonate monosodium (IBP) were loaded on Ca10(PO4)6(OH)1F1 ceramic bodies by stirring the ceramic bodies in 0.04M BP solutions. Injectable acrylic cements based on self-curing formulations of methyl methacrylate (MMA) and vitamin E were loaded with APBP and IBP. The incorporation of ABBP was confirmed by MAS-NMR spectroscopy. Modified powder shows two different phosphorous environments, the first one at 2.91 ppm can be assigned to the apatite base and the second one at 18.0 ppm has to be attributed to the phosphonic group of the ABBP. The IBP addition on ceramic surfaces did not decrease the number of osteoclast colonies and appeared to improve the performance of the HA as a surface for osteoblast culture. A therapeutic dosage of APBP and IBP can be achieved from acrylic cements that showed lack of toxicity and an increased cellular activity and proliferation, Financial support from CICYT, Spain (MAT2004-01654) and NoE EXPERTISSUES (UE contract Nº: 500283-2) is acknowledged. Mar Fernández and Luis M. Rodríguez Lorenzo are supported by the Ramón y Cajal Programme, MEC-Spain

The effects of heat treatment time and temperature on the delivery behaviour of Ibuprofen from hydroxyapatite particles were investigated in this study. The drug release was seen to follow Fickian diffusion for the initial period of release for all heat treatment conditions. The gradient of Fickian release increased with (1) increasing crystallite size, attributed to the decreasing amount of boundary area, and (2) with decreasing surface area, due to the reduction in porosity and hence tortuosity within the apatite particles. This study has shown that altering the heat treatment conditions used to calcine hydroxyapatite may alter its drug delivery abilities, whereby calcination temperature was noted to influence the drug release behaviour to a greater extent than calcination time.