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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

Organic-inorganic hybrid materials overcome drawbacks associated with alginate hydrogels. In this work, covalently coupled silica-alginate hybrids were prepared by Schiff base formation and sol-gel reaction using alginate dialdehyde (ADA), (3- Aminopropyl) triethoxysilane (APTES), and APTES/tetraethylorthosilicate (TEOS) precursors. The influence of the polysaccharide/inorganic ratio, the nature of the inorganic precursor and the ionic crosslinking ability are studied. Prepared hybrids were characterized by FT-IR, 13C and 29Si -NMR spectroscopies, SEM, and rheology. For ADA/APTES hybrids, at higher ADA content, Schiff base formation is predominant, but at lower ADA content, the sol-gel reaction is prevalent. However, the progress of the sol-gel reactions for ADA/(APTES+TEOS), is favored with higher ADA compositions. Introducing a posterior ionic crosslinking treatment was possible, increasing the moduli in ADA/(APTES+TEOS) hybrids from 86207Pa for 1.5 ADA/Si to 362171Pa for 1.5 ADA/Si-Ca. In-situ ADA-Silica hybrid hydrogels containing both ionic and covalent crosslinking can be successfully synthesized with the proposed method., Instituto Politécnico Nacional, México (IPN-SIP 20196660 and IPN-SIP 20201294), AEI/FEDER,UE (DPI2017-90147-R), CONACYT scholarship.

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.

The search of suitable combinations of stem cells, biomaterials and scaffolds manufacturing methods have become a major focus of research for bone engineering. The aim of this study was to test the potential of dental pulp stem cells to attach, proliferate, mineralize and differentiate on 3D printed polycaprolactone (PCL) scaffolds. A 100% pure Mw: 84,500 +- 1000 PCL was selected. 5 x 10 x 5 mm3 parallelepiped scaffolds were designed as a wood-pilled structure composed of 20 layers of 250 microm in height, in a non-alternate order ([0,0,0,90,90,90º]). 3D printing was made at 170 ºC. Swine dental pulp stem cells (DPSCs) were extracted from lower lateral incisors of swine and cultivated until the cells reached 80% confluence. The third passage was used for seeding on the scaffolds. Phenotype of cells was determined by flow Cytometry. Live and dead, Alamar blue™, von Kossa and alizarin red staining assays were performed. Scaffolds with 290 + 30 micron strand diameter, 938 x 80 micron pores in the axial direction and 689 x 13 micron pores in the lateral direction were manufactured. Together, cell viability tests, von Kossa and Alizarin red staining indicate the ability of the printed scaffolds to support DPSCs attachment, proliferation and enable differentiation followed by mineralization. The selected material-processing technique-cell line (PCL-3D printing-DPSCs) triplet can be though to be used for further modelling and preclinical experiments in bone engineering studies., Grant PAPIIT IA207420, UNAM, México and AEI/FEDER, UE (DPI2017-90147-R) Spain.

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.

This review focuses on recently developed alginate injectable hydrogels and alginate composites for applications in bone tissue regeneration, and it evaluates the alternatives to overcome the problems that avoid their utilization in the field. Section 2 covers the properties of alginates that have made them useful for medical applications, in particular their ionic gelling ability for preparing injectable compositions used as delivery drugs systems. The advantages and shortcomings of these preparations are revised together with the chemical modifications assayed. Section 3 describes how it has been taken advantage of alginates into the new field of biofabrication and the developments in bone engineering. The state of the art of this field is reviewed. Finally in section 4, new developments and approaches that in opinion of the authors can lead to a breakthrough in bone tissue engineering using alginates are introduced., Instituto Politécnico Nacional, Mexico (IPN-SIP 20196660), AEI/FEDER, UE (DPI2017-90147-R)., CONACYT scholarship

Two series of segmented polyurethanes were obtained and their mechanical and thermal properties as well as their biodegradability and cytotoxicity were evaluated. The chemical nature of the polyurethanes was varied by using either 1,4 butanediol (poly-ester-urethanes, PEUs) or l-lysine ethyl ester dihydrochloride (poly-ester-urea-urethanes, PEUUs) as chain extenders. Results showed that varying the hard segment influenced the thermal and mechanical properties of the obtained polymers. PEUs showed strain and hardness values of about 10&ndash, 20 MPa and 10&ndash, 65 MPa, respectively. These values were higher than the obtained values for the PEUUs due to the phase segregation and the higher crystallinity observed for the polyester-urethanes (PEUs), phase segregation was also observed and analyzed by XRD and DSC. Moreover, both series of polymers showed hydrolytic degradation when they were submerged in PBS until 90 days with 20% of weight loss. In vitro tests using a Human Osteoblastic cell line (Hob) showed an average of 80% of cell viability and good adhesion for both series of polymers.

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 aim of this work is to evaluate the potential of cryogels to be used as scaffolds in tissue engineering. Scaffolds based on the α-tricalcium phosphate reinforced PDMAEMA (Poly(dimethyl aminoethyl methacrylate))/PHEMA (poly(hydroxyethyl methacrylate)) system were prepared and human trabecular bone-derived cells (HTBs) and bone marrow derived-mesenchymal stem cells (BM-MSCs) cultured on them. Several features, such as porosity, pore shape, molecular weight between crosslinks and mesh size, are studied. The most suitable PDMAEMA/PHEMA ratio for cell proliferation has been assessed and the viability, adhesion, proliferation and expression of osteoblastic biochemical markers are evaluated. The PDMAEMA/PHEMA ratio influences the scaffolds porosity. Values between 53% ± 5.7% for a greater content in PHEMA and 75% ± 5.5% for a greater content in PDMAEMA have been obtained. The polymer ratio also modifies the pore shape. A greater content in PDMAEMA leads also to bigger network mesh size. Each of the compositions were non-cytotoxic, the seeded cells remained viable for both BM-MSCs and HTBs. Thus, and based on the structural analysis, specimens with a greater content in PDMAEMA seem to provide a better structural environment for their use as scaffolds for tissue engineering. The α-tricalcium phosphate incorporation into the composition seems to favor the expression of the osteogenic phenotype., We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI)

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.

The purpose of this work is to study the dissolution mechanism of SiO2-based bioactive hybrid materials containing both CaO and P2O5 in their structures and to determine the influence of apatite crystallization over the surface features of the hybrids during degradation. Hybrid materials were synthesized using sol–gel method. Tetraethoxysilane (TEOS), hydroxyl terminated polydimethylsiloxane (PDMS), Ca(NO3)2·4H2O, and triethyl phosphate (TEP) were used as reactants. The degradation and bioactivity of the hybrid materials were tested by soaking the specimens into simulated body fluid (SBF). Raman spectroscopy, tensiometry and N2 adsorption/desorption curves were used to measure the changes during the degradation experiments. Several mathematical approaches have been taken to analyze the results. The growth of an apatite layer on the surface of SiO2-modified PDMS-P2O5-CaO hybrid materials occurs together with degradation of the silica-based matrix. The dissolution kinetics depends upon the composition of the material. It varies from a surface-driven mechanism in the case of low-P2O5 samples to a degradation path which fits into a Weibull type kinetic model, typical of matrix dissolution processes in materials enriched in P2O5. During degradation, the surface parameters, fractal constant and anisotropy of the pores were determined. The slight increase of the fractal constant in low-containing P2O5 materials suggests the formation of a homogeneous silica-like layer in the first stage of degradation, which also works as anchoring nucleus for subsequent apatite formation. In all the cases, the degradation leads to ink-bottle shaped pores, increasing their volume as degradation occurs, but keeping their neck shape., This work was supported by SIP-IPN 20150064 Project (Mexico), DGICYT Project, MAT2014-51918-C2-1-R (Spain), Fundación General CSIC (Programa ComFuturo) (A. Tamayo). DA Sánchez – Téllez also acknowledges CONACYT for the scholarship given.

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.