Design and Manufacture of Bone Cements Based on Calcium Sulfate Hemihydrate and Mg, Sr-Doped Bioactive Glass.

In the present study, a novel composite bone cement based on calcium sulfate hemihydrate (CSH) and Mg, Sr-containing bioactive glass (BG) as solid phase, and solution of chitosan as liquid phase were developed. The phase composition, morphology, setting time, injectability, viscosity, and cellular responses of the composites with various contents of BG (0, 10, 20, and 30 wt.%) were investigated. The pure calcium sulfate cement was set at approximately 180 min, whereas the setting time was drastically decreased to 6 min by replacing 30 wt.% glass powder for CSH in the cement solid phase. BG changed the microscopic morphology of the set cement and decreased the size and compaction of the precipitated gypsum phase. Replacing the CSH phase with BG increased injection force of the produced cement; however, all the cements were injected at a nearly constant force, lower than 20 N. The viscosity measurements in oscillatory mode determined the shear-thinning behavior of the pastes. Although the viscosity of the pastes increased with increasing BG content, it was influenced by the frequency extent. Pure calcium sulfate cement exhibited some transient cytotoxicity on human-derived bone mesenchymal stem cells and it was compensated by introducing BG phase. Moreover, BG improved the cell proliferation and mineralization of extracellular matrix as shown by calcein measurements. The results indicate the injectable composite cement comprising 70 wt.% CSH and 30 wt.% Mg, Sr-doped BG has better setting, mechanical and cellular behaviors and hence, is a potential candidate for bone repair, however more animal and human clinical evaluations are essential.

Tissue-engineered small-diameter vascular grafts containing novel copper-doped bioactive glass biomaterials to promote angiogenic activity and endothelial regeneration.

Small-diameter vascular grafts frequently fail because of obstruction and infection. Despite the wide range of commercially available vascular grafts, the anatomical uniqueness of defect sites demands patient-specific designs. This study aims to increase the success rate of implantation by fabricating bilayer vascular grafts containing bioactive glasses (BGs) and modifying their composition by removing hemostatic ions to make them blood-compatible and to enhance their antibacterial and angiogenesis properties. The porous vascular graft tubes were 3D printed using polycaprolactone, polyglycerol sebacate, and the modified BGs. The polycaprolactone sheath was then wrapped around the 3D-printed layer using the electrospinning technique to prevent blood leakage. The results demonstrated that the incorporation of modified BGs into the polymeric matrix not only improved the mechanical properties of the vascular graft but also significantly enhanced its antibacterial activity against both gram-negative and gram-positive strains. In addition, no hemolysis or platelet activity was detected after incorporating modified BGs into the vascular grafts. Copper-releasing vascular grafts significantly enhanced endothelial cell proliferation, motility, and VEGF secretion. Additionally, In vivo angiogenesis (CD31 immunofluorescent staining) and gene expression experiments showed that copper-releasing vascular grafts considerably promoted the formation of new blood vessels, low-grade inflammation (decreased expression of IL-1ß and TNF-α), and high-level angiogenesis (increased expression of angiogenic growth factors including VEGF, PDGF-BB, and HEBGF). These observations indicate that the use of BGs with suitable compositional modifications in vascular grafts may promote the clinical success of patient-specific vascular prostheses by accelerating tissue regeneration without any coagulation problems.

Evaluation of UV photofunctionalization effect on ultrastructural properties of SLA titanium disks: An in vitro study.

Background: The success rate of dental implants diminishes over time; the lack of osseointegration and infection are the major causes of most implant failures. One of the effective methods to improve the surface properties is to irradiate ultraviolet (UV) light. This study investigated the effect of UV photofunctionalization on the ultrasuperficial properties of sandblasted, large-grit, acid-etched (SLA) titanium discs. Methods: In this in vitro study, 24 sandblasted and acid-etched titanium discs, with a lifespan of more than four weeks, were categorized into three groups (n=8): control, ultraviolet C (UVC), and ultraviolet B (UVB). Then, they were exposed to a UV light source for 48 hours at a 1-cm distance. In addition to measuring the contact angle between the liquid and the disc surface in each of the three groups, the atomic concentrations of carbon, oxygen, and nitrogen atoms were measured at three different sites on each disc. One-way ANOVA and post hoc Tukey tests were used to analyze data. Results: The mean concentration of carbon atoms significantly differed in the control, UVC, and UVB groups (P<0.001). The mean concentrations of nitrogen atoms differed significantly between the three groups (P<0.001). However, the mean concentrations of oxygen atoms were not significantly different between the three groups. In examining the contact angle, wettability was higher in the UVC group than in the UVB group and higher in the UBV group than in the control group. Conclusion: Photofunctionalization with UV light significantly decreased carbon and nitrogen concentrations on the surface of titanium implants, indicating that the implant's superficial hydrocarbons were eliminated. It was observed that UVC photofunctionalization was more effective than UVB photofunctionalization in reducing superficial contamination and improving wettability.

Preparation and characterization of injectable gelatin/alginate/chondroitin sulfate/α-calcium sulfate hemihydrate composite paste for bone repair application.

In this study, a group of injectable composite pastes with a novel formulation consisting of two inorganic components: α-calcium sulfate hemihydrate (α-CSH, P/L = 1.8-2.1 g/ml) and calcium-deficient hydroxyapatite (CDHA, P/L = 0.1 g/ml) nanoparticles; and three biopolymers: gelatin (2, 4 wt. %), alginate (1, 1.5 wt. %), and chondroitin sulfate (0.5 wt. %) were carefully prepared and thoroughly characterized with commensurate characterizations. The composite sample composed of gelatin (2 wt. %), alginate (1.5 wt. %), chondroitin sulfate (0.5 wt. %), and also CDHA nanoparticles and α-CSH with P/L ratios of 0.1 and 2.1 g/ml, respectively, exhibited optimal properties in terms of injectability, anti-washout performance, and rheological characteristics. After 14 days of immersion of the chosen sample in the simulated body fluid medium, a dense layer of apatite was formed on the surface of the composite paste. The cellular in vitro tests, such as 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay (MTT), alkaline phosphatase assay, 4',6-diamidino-2-phenylindole staining, and cellular attachment, revealed the desirable response of MG-63 cells to the composite paste. The chondroitin sulfate significantly improved the injectability, anti-washout performance, and cellular response of the samples. Considering the promising features of the composite paste prepared in this research work, it could be considered as an alternative injectable bioactive material for bone repair applications.[Formula: see text].

3D direct printing of composite bone scaffolds containing polylactic acid and spray dried mesoporous bioactive glass-ceramic microparticles.

In this study, a three-dimensional composite scaffold is proposed consisting of polylactic acid and spray dried glass-ceramic microparticles (SGCMs). The compositional and structural characterization showed that the obtained spray dried powder formed as glass-ceramic (GC) with a completely interconnected porosity structure. Before direct printing of scaffolds, the rheological behavior of polylactic acid (PLA) and PLA-GC (PLA matrix containing SGCMs) inks were investigated. The PLA-GC composite ink represents sharper shear-thinning behavior and higher loss and storage modulus comparable to that of pure PLA. Microscopic observations and elemental mapping elements showed that 3D scaffolds had well-defined interconnected porosity and uniform distribution of the glass-ceramic particles. Mechanical tests indicated that compression strength is dependent on the scaffold porosity and the presence of SGCMs. Apatite formation evaluation besides ion release study showed better biomineralization capacity of PLA-GC scaffolds, as larger and denser sediments formed on the PLA-GC scaffolds after 7- and 14-day soaking. The preliminary cell response was studied with primary human mesenchymal stem cells (hMSCs) and revealed that SGCMs improved cell adhesion and viability and ALP activity. The appropriate combination of the biomaterials/methods to fabricate 3D porous constructs and their available bioactivity and biocompatibility, both being important characteristics for bone tissue engineering applications.

Platelet-rich plasma-hyaluronic acid/chondrotin sulfate/carboxymethyl chitosan hydrogel for cartilage regeneration.

In this study, the chondrogenic potential of hyaluronic acid/chondrotin sulfate/carboxymethyl chitosan hydrogels with adipose-derived mesenchymal stem cells (ADMSCs) was evaluated. Here, hyaluronic acid, chondrotin sulfate, and carboxymethyl chitosan were used as the substrate for cartilage tissue engineering in which the hydrogel is formed due to electrostatic and hydrogen bonds through mixing the polymers. Because of the instability of this hydrogel in the biological environment, 1-ethyl-3-(3-dimethylaminopropyl-carbodiimide hydrochloride/N-hydroxy-succinimide was used as a crosslinker to increase the hydrogel stability. The hydrogels showed reasonable stability due to the combined effect of self-crosslinking and chemical crosslinking. The cells were treated with the prepared hydrogel samples for 14 and 21 days in nondifferentiation medium for evaluation of the cellular behavior of ADMSCs. Gene expression evaluation was performed, and expression of specific genes involved in differentiation was shown in the crosslinked hydrogel with platelet-rich plasma (PRP) (H-EN-P) had increased the gene expression levels. Quantification of immunofluorescence intensity indicated the high level of expression of SOX9 in H-EN-P hydrogel. Based on the results, we confirmed that the presence of PRP and the similarity of the hydrogel constituents to the cartilage extracellular matrix could have positive effects on the differentiation of the cells, which is favorable for cartilage tissue engineering approaches.

Sol-Gel Synthesis, in vitro Behavior, and Human Bone Marrow-Derived Mesenchymal Stem Cell Differentiation and Proliferation of Bioactive Glass 58S.

Background: Bioactive glasses 58S, are silicate-based materials containing calcium and phosphate, which dissolved in body fluid and bond to the bone tissue. This type of bioactive glass is highly biocompatible and has a wide range of clinical applications. Methods: The 58S glass powders were synthesized via sol-gel methods, using tetraethyl orthosilicate, triethyl phosphate, and calcium nitrate, as precursors. Upon the analyses of phase and chemical structures of bioactive glass in different gelation times (12, 48, and 100 h), the appropriate heat treatment (at 525, 575, and 625 °C) was performed to eliminate nitrate compounds and stabilize the glass powder samples. The in vitro assay in SBF solution revealed the bioactivity of the synthesized 58S glass through the morphological (SEM), chemical structure (FTIR), release of calcium, phosphorous and silicon elements, pH variations, and weight loss measurements. The behavior of MSCs in the presence of bioactive glass powders was studied by MTT cytotoxicity, cell staining, ALP activity and biomineralization tests, as well as by the evaluation of ALP, osteocalcin, osteonectin, collagen I, and RUNX2 gene expression. Results: The results confirmed a gelation time of 100 h and a calcination temperature of 575 °C at optimal conditions for the synthesis of nitrate-free bioactive glass powders. Conclusion: The glass spherical nanoparticles in the range of 20-30 nm possess the improved bioactivity and osteogenic properties as demanded for bone tissue engineering.

Poly(hydroxybutyrate-co-hydroxyvalerate) Porous Matrices from Thermally Induced Phase Separation.

Thermally induced phase separation followed by freeze drying has been used to prepare biodegradable and biocompatible scaffolds with interconnected 3D microporous structures from poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) copolymers containing 5 and 12 wt % of 3-hydroxyvalerate (HV). Solutions of PHBV in 1,4-dioxane, underwent phase separation by cooling under two different thermal gradients (at -25 °C and -5 °C). The cloud point and crystallization temperature of the polymer solutions were determined by turbidimetry and differential scanning calorimetry, respectively. Parameters affecting the phase separation mechanism such as variation of both the cooling process and the composition of the PHBV copolymer were investigated. Afterwards, the influence of these variables on the morphology of the porous structure and the final mechanical properties (i.e., rigidity and damping) was evaluated via scanning electron microscopy and dynamic mechanical thermal analysis, respectively. While the morphology of the scaffolds was considerably affected by polymer crystallization upon a slow cooling rate, the effect of solvent crystallization was more evident at either high hydroxyvalerate content (i.e., 12 wt % of HV) or high cooling rate. The decrease in the HV content gave rise to scaffolds with greater stiffness because of their higher degree of crystallinity, being also noticeable the greater consistency of the structure attained when the cooling rate was higher. Scaffolds were fully biocompatible supports for cell adhesion and proliferation in 3D cultures and show potential application as a tool for tissue regeneration.

Bioactive and biostable hyaluronic acid-pullulan dermal hydrogels incorporated with biomimetic hydroxyapatite spheres.

In this study, hyaluronic acid-pullulan injectable hydrogels were incorporated with biomimetic hydroxyapatite spheres and were modified using silane coupling agents in order to improve the physicochemical, mechanical, and biological performance of hydrogels. So the biomimetic hydroxyapatite spheres were synthesized through immersion of gelatin-siloxane microspheres in the simulated body fluid. The results of field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction spectra confirmed the formation of hydroxyapatite on the surface of hybrid spheres. The morphology observation of the prepared hydrogels confirmed the uniform distribution of hydroxyapatite spheres in gel structure. The chemical characterization proved the possible interactions between the polymers and the created complex with a silane coupling agent to provide more durability. Improvement of storage modulus and viscosity indicated the positive role of hydroxyapatite spheres on the stability and long-lasting durability of hydrogels. A slight reduction was observed in the absorption capacity and water retention in hybrid hydrogels; even though, the great resistance to enzymatic biodegradation led to higher durability of hydroxyapatite-contained gels. Improvement in L-929 fibroblast cell adhesion and spreading especially around the biomimetic hydroxyapatite spheres along with higher cell viability demonstrated the initial potential of hydrogels for further pre-clinical and clinical studies in order to recommend the gels for dermal rejuvenation applications.

A facile method to synthesize mussel-inspired polydopamine nanospheres as an active template for in situ formation of biomimetic hydroxyapatite.

In this study, Mussel-inspired polydopamine (PDA) nanospheres were synthesized via spontaneous oxidative polymerization of dopamine hydrochloride (dopa-HCl) in a deionized water-alcohol mixed solvent at room temperature and atmospheric air, under alkaline condition. Field-emission scanning electron microscopy (FE-SEM) demonstrated production of sphere-like shape with a smooth surface and tunable size, while monodispersity increased by utilizing isopropanol instead of ethanol owing to lower Ra values based on Hansen solubility parameter (HSP) theory. Dropwise addition of monomer played an undeniable role in the fabrication of uniform and smaller spheres. The difference of the charge repulsion of constructs in the range of pH led to different dispersive behavior in a variety of solvents, exhibiting versatile applications. The presence of active functional groups on the surface of PDA spheres made them an appropriate option for PDA-assisted biomimetic mineralization of hydroxyapatite (HA), which is the result of the interaction between abundant catecholamine moieties in PDA and Ca+2 ions in simulated body fluid. Bio-adhesive nature of PDA in water and the presence of amino and hydroxyl functional groups support desirable L929 mouse fibroblast cell spreading. The viability of >90% fibroblast cells proved the biocompatibility of polymerized structure. All the achievements indicated that PDA nanospheres provide a biocompatible and bioactive template for green synthesizing hydroxyapatite and the innovative basis for further tissue engineering applications.

Evaluation of hMSCs Response to Sodium Alginate / Bioactive Glass Composite Paste: Effect of CaO/P2O5, Sodium Alginate Concentration and P/L Ratios.

BACKGROUND: Bioactive glasses with different compositions have been extensively used as bone tissue engineering. Preparation, development and characterization of alginate pastes containing bioglass for bone repair applications were the purposes of this study. OBJECTIVE: The injectable bone pastes were produced from sol-gel derived bioactive glass nanoparticles with various CaO/P2O5 ratios of 19, 9.5 and 4.75 and sodium alginate solutions with different concentrations of 1, 2 and 4 wt.%. The effect of CaO/P2O5 and powder to liquid (P/L) ratios and alginate concentration on injectability, biodegradation, rheological properties, bioactivity and cellular behavior of the pastes have been studied. The behavior of human mesenchymal stem cells (hMSCs) in the presence of the pastes was assessed by MTT assay, biomineralization assay, ALP activity, Acridine orange staining and Alizarin red staining tests. RESULTS: By adding sodium alginate, the pastes exhibited a thixotropy behavior. The storage modulus of all pastes was larger than the loss modulus in the frequency range of 0.1-100 s-1. Cytotoxicity evaluation results revealed that there was a critical amount of bioactive glass in pastes which are above the limit; the viability of hMSCs will be at risk. The pastes made of bioactive glass nanoparticles with CaO/P2O5 = 9.5 and sodium alginate 1% with P/L ratio of 0.8 showed optimum behavior in terms of mineral carrying capacity, injectability characteristics, accellular bioactivity in SBF, loss weight and wash out behavior, proliferation and differentiation of hMSCs. CONCLUSION: According to the results, the pastes prepared with sodium alginate solution and bioactive glass nanoparticles can be beneficial in bone tissue engineering.

Leuprolide Acetate Release Study from γ-Irradiated PLGA-based In Situ Forming System.

BACKGROUND: It is well known that the properties of polymers can be altered by exposure to γ- ray. γ-irradiation has been used as a sterilization method for polymeric drug delivery devices, and its drug release profile must not be significantly changed. In this study, the effect of γ-irradiation on the release profile of leuprolide acetate from PLGA-based in situ forming system was investigated. METHODS: Poly(lactide-co-glycolide) (PLGA) was dissolved in N-methylpyrrolidinone (NMP) and irradiated with a total dose of 8 kGy γ-ray emitted by a 60Co source. Then, leuprolide acetate was added to the polymer solution. PLGA-based in situ forming systems were prepared by injecting some specific amount of prepared solution into a buffer phosphate pH 7.4 at 37 °C. The effects of γ-ray on drug release profiles, morphology of matrices and thermal properties as well as stability of polymer were evaluated. RESULTS: The results showed that γ-irradiation causes a decrease in glass transition temperature (Tg) of PLGA from 43.4 to 38.1°C. A reduction in molecular weight of PLGA by about 17.8 % was found as consequence of radiolytic degradation. The morphological studies of PLGA matrices confirmed that the irradiated sample had higher porosity than the non-irradiated sample. It is found that the amount of released leuprolide acetate from irradiated matrix was increased by about 1.6 times after 33 days compared to the nonirradiated ones. In vitro drug release experimental data were fitted using the Gallagher- Corrigan model which indicated that diffusion and degradation were the predominant mechanisms of drug release. CONCLUSION: Accordingly, leuprolide acetate was released faster from the irradiated matrix compared to the non- irradiated matrix.

In situ-forming PLGA implants loaded with leuprolide acetate/ß-cyclodextrin complexes: mathematical modelling and degradation.

Drug release mechanism of in situ-forming implants (ISIs) based on poly(lactic acid-co-glycolic acid) (PLGA) loaded with leuprolide acetate/ß-cyclodextrin (LA/ß-CD) complexes via fitting with four diffusion-based semi-empirical models were studied. The release rate constants and release exponent of ISIs were calculated. The main drug release mechanism was Fickian diffusion. The LA diffusion coefficient and release constant were decreased via increasing the portion of ß-CD in complexes. The release curve was parabolic, with a higher initial slope and then consistent with the exponential. All ISIs containing LA/ß-CD complexes better fitted with the Korsmeyer-Peppas, Weibull and Peppas-Sahlin models rather than first-order model. Furthermore, the effect of LA/ß-CD complexation on the degradation of ISIs was studied through scanning electron microscopy (SEM). Results showed that hydrophilic nature of ß-CD facilitated the surface erosion of PLGA chains, however after 18 d, ISI-1/10 had still a proper structural strength, due to no hydrolytic degradation of ß-CD in this implant.

Rheological evaluations and in vitro studies of injectable bioactive glass-polycaprolactone-sodium alginate composites.

Composite pastes composed of various amounts of melt-derived bioactive glass 52S4 (MG5) and polycaprolactone (PCL) microspheres in sodium alginate solution were prepared. Rheological properties in both rotatory and oscillatory modes were evaluated. Injectability was measured as injection force versus piston displacement. In vitro calcium phosphate precipitation was also studied in simulated body fluid (SBF) and tracked using scanning electron microscopy, X-ray diffraction and FTIR analyses. All composite pastes were thixotropic in nature and exhibited shear thinning behavior. The magnitude of thixotropy decreased by adding 10-30 wt% PCL, while further amounts of PCL increased it again. Moreover, the composites were viscoelastic materials in which the elastic modulus was higher than viscous term. The pastes which were just made of MG5 or PCL had poor injectability, whereas the composites containing both of these constituents exhibited reasonable injectability. All pastes revealed adequate structural stability in contact with SBF solution. In vitro calcium phosphate precipitation was well observed on the paste made of MG5 and somewhat on the pastes with 10-40 wt% PCL, however the precipitated layer was amorphous in nature. Overall, the produced composites may be appropriate as injectable biomaterials for non-invasive surgeries but more biological evaluations are essential.

Aqueous stability of leuprolide acetate: effect of temperature, dissolved oxygen, pH and complexation with ß-cyclodextrin.

In the present research, the aqueous stability of leuprolide acetate (LA) in phosphate buffered saline (PBS) medium was studied (pH = 2.0-7.4). For this purpose, the effect of temperature, dissolved oxygen and pH on the stability of LA during 35 days was investigated. Results showed that the aqueous stability of LA was higher at low temperatures. Degassing of the PBS medium partially increased the stability of LA at 4 °C, while did not change at 37 °C. The degradation of LA was accelerated at lower pH values. In addition, complexes of LA with different portions of ß-cyclodextrin (ß-CD) were prepared through freeze-drying procedure and characterized by Fourier transform infrared (FTIR) and differential scanning calorimetry (DSC) analyses. Studying their aqueous stability at various pH values (2.0-7.4) showed LA/ß-CD complexes exhibited higher stability when compared with LA at all pH values. The stability of complexes was also improved by increasing the portion of LA/ß-CD up to 1/10.

Topography and nanostructural evaluation of chemically and thermally modified titanium substrates.

In this research, the effects of chemical and thermal treatment on the morphological and compositional aspects of titanium substrates and so, potentially, on development of biomimetic bone like layers formation during simulated body fluid (SBF) soaking was investigated. The HF, HF/HNO3 and NaOH solutions were used for chemical treatment and some of alkali-treated samples followed a heat treatment at 600°C. The treated samples before and after soaking were subjected to material characterization tests using scanning electron microscopy (SEM), X-ray diffraction (XRD) and atomic force microscopy (AFM). White light interferometry (WLI) was used to determine the roughness parameters such as Ra, Rq, RKu and Rsk. The significance of the obtained data was assessed using ANOVA variance analysis between all samples. It was observed that the reaction at grain boundaries and sodium titanate intermediate layers play a great role in the nucleation of calcium phosphate layers. Based on the obtained results in this work, the calcium phosphate microstructure deposited on titanium substrates was more affected by chemical modification than surface topography.

Manufacturing of biodegradable polyurethane scaffolds based on polycaprolactone using a phase separation method: physical properties and in vitro assay.

BACKGROUND: Biodegradable polyurethanes have found widespread use in soft tissue engineering due to their suitable mechanical properties and biocompatibility. METHODS: In this study, polyurethane samples were synthesized from polycaprolactone, hexamethylene diisocyanate, and a copolymer of 1,4-butanediol as a chain extender. Polyurethane scaffolds were fabricated by a combination of liquid-liquid phase separation and salt leaching techniques. The effect of the NCO:OH ratio on porosity content and pore morphology was investigated. RESULTS: Scanning electron micrographs demonstrated that the scaffolds had a regular distribution of interconnected pores, with pore diameters of 50-300 µm, and porosities of 64%-83%. It was observed that, by increasing the NCO:OH ratio, the average pore size, compressive strength, and compressive modulus increased. L929 fibroblast and chondrocytes were cultured on the scaffolds, and all samples exhibited suitable cell attachment and growth, with a high level of biocompatibility. CONCLUSION: These biodegradable polyurethane scaffolds demonstrate potential for soft tissue engineering applications.

Effect of functionalized carbon nanotubes on the synthesis of hydroxyapatite nanoparticles.

The purpose of this study was to investigate the effect of the functionalized carbon nanotubes (CNT) on the nucleation of the HA nanoparticles. In this work, solutions of calcium nitrate tetra hydrate and diamonium hydrogen phosphate in water were used as Ca, P precursors. The former solution was added to an aqueous suspension of MWNTs-COOH. Different CNT functionalization percentage ratios of 1%, 2%, 3%, 4% and 5% were examined. X-ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FT-IR) experiments confirmed that the resulting powders were composed of hydroxyapatite. The Scanning Electron Microscopy (SEM) images illustrated a short distance effect of CNTs on the formation of the HA nanoparticles. In addition, a more detailed observation performed by Transmission Electron Microscopy (TEM) depicted the flake-like morphology of the nanoparticles. Based on the results of this research, the crystallinity decreased due to the CNT addition to the synthesis media. The sample containing a CNT functionality percentage of 5% revealed a preferred crystalline orientation compared with the samples composed of less CNT functionality percentage of 1%, 2%, 3% and 4%.

Polyurethane/fluor-hydroxyapatite nanocomposite scaffolds for bone tissue engineering. Part I: morphological, physical, and mechanical characterization.

In this study, new nano-fluor-hydroxyapatite (nFHA)/polyurethane composite scaffolds were fabricated for potential use in bone tissue engineering. Polyester urethane samples were synthesized from polycaprolactone, hexamethylene diisocyanate, and 1,4-butanediol as chain extender. Nano fluor-hydroxyapatite (nFHA) was successfully synthesized by sol-gel method. The solid-liquid phase separation and solvent sublimation methods were used for preparation of the porous composites. Mechanical properties, chemical structure, and morphological characteristics of the samples were investigated by compressive test, Fourier transform infrared, and scanning electron microscopy (SEM) techniques, respectively. The effect of nFHA powder content on porosity and pore morphology was investigated. SEM images demonstrated that the scaffolds were constituted of interconnected and homogeneously distributed pores. The pore size of the scaffolds was in the range 50-250 µm. The result obtained in this research revealed that the porosity and pore average size decreased and compressive modulus increased with nFHA percentage. Considering morphological, physical, and mechanical properties, the scaffold with a higher ratio of nFHA has suitable potential use in tissue regeneration.