Fluoride incorporation in hydroxyapatite/gelatin nanocomposite

The incorporation of fluoride ion into hydroxyapatite (HAp)/gelatin (GEL) nanocomposite was investigated. The F(-) ion incorporation into OH(- )site of HAp phase was an energetically active process, which could be confirmed from the spray solution reaction. The precursors of Ca(2+) in water and phosphates in aqueous gelatin were mixed in the humidified air chamber by air spray, and then the precipitates were aged in a reactor. The F(-) ion precursor was dissolved in the starting solution of Ca(OH)(2) in water, and the resulted Ca(OH, F)(2) complex droplets induced the formation of stable fluoroapatite (F, OH)Ap. The reaction kinetics could be assumed from TEM morphology with ED, XRD and FT-IR analysis.     

Preparation and characterization of hydroxyapatite/collagen nanocomposite gel

The self-organized hydroxyapatite/colagen (HAp/Col) nanocomposite fiber (79.6/20.4 weight ratio) was synthesized by a co-precipitation method using Ca(OH)2, H3PO4, and Col as starting substances. The gelation of the nanocomposite is essential in the application of the scaffold for bone tissue engineering. We successfully prepared HAp/Col nanocomposite gels by a facile novel method using a sodium phosphate buffer at pH 6.8. The water-insoluble nanocomposite was homogeneously dispersed in the buffer to form a viscous mixture, and gels were obtained after incubating of the mixture at 37 degrees C. The mechanical strength of the gels was analyzed against the incubation time. The demineralized gel with EDTA had the typical nanostructure of native type I Col fibers from the results of scanning electron microscopy (SEM) and atomic force microscopy (AFM); the dense network of type I Col nano-fibers below 100 nm in diameter, and the periodic pattern of 68.8+/-4.4 nm (mean +/- SD) along the fibers were observed. The gelation of the HAp/Col nanocomposite in the buffer is attributed to the physical cross-linking through entanglement of the reconstituted Col fibrils.     

Injectable silk/hydroxyapatite nanocomposite hydrogels with vascularization capacity for bone regeneration

Localized and sustained osteogenic-angiogenic stimulation to bone defects is critical for effective bone repair.Here,desferrioxamine(DFO)was loaded on silk fibroin nanofibers and blended with hydroxyapatite nanorods(HA),forming injectable DFO-loaded silk fibroin-HA nanocomposite hydrogels.The composite hydrogels remained homogeneous distribution of HA with high ratio(60%)and also higher stiffness than that of pure silk fibroin nanofiber hydrogels,which provided stable osteogenic stimulation niches for tissue regeneration.Without the scarify of injectability,the hydrogels achieved slow delivery of DFO for above 60 days,resulting in suitable angiogenesis in vitro and in vivo and better osteogenesis than DFO-free systems.Compared to previous injectable silk fibroin-HA hydrogels,the introduction of vascularization capacity further stimulated the osteogenic differentiation of stem cells and accelerated new bone formation.Quicker and better bone healing were detected at defect sites after the injection of DFO-loaded nanocomposite hydrogels,indicating the effective synergistic effect of osteogenic and angiogenic cues.This work provides a simple and effective strategy of introducing angiogenic cues to bone matrices.We believe that the injectable nanocomposite hydrogels are suitable for the regeneration of bone tissues.     

A novel method for the fabrication of homogeneous hydroxyapatite/collagen nanocomposite and nanocomposite scaffold with hierarchical porosity

Homogeneous nanocomposites composed of hydroxyapatite (HAp) and collagen were synthesized using a novel in situ precipitation method through dual template-driven. The morphological and componential properties of nanocomposites were investigated. The HAp particulates, in sizes of about 50–100 nm, were distributed homogeneously in the organic collagen hydrogel. Highly magnified TEM observation showed that HAp inorganic particles were composed of fine sub-particles (2–5 nm) without regular crystallographic orientation. Based on these homogeneous nanocomposites, a novel HAp/collagen nanocomposite scaffold with hierarchical porosity was prepared by multilevel freeze-drying technique. Compared to other conventional scaffolds for tissue engineering, this novel in situ method endows synthesized composite scaffolds with unique morphology—ultrafine HAp particles dispersed homogenously in collagen at nano level and the foam scaffold with hierarchical pore structures. The mechanical performance increased obviously compared with neat collagen. These results provided an efficient approach toward new biomimetic tissue scaffold for the biomedical applications with enhanced intensity/bioactivity and controlled resorption rates. This novel method, we expect, will lead to a wide application in many other hydrogel systems and may be useful for fabrication of various homogeneous inorganic/organic nanocomposites.     

Cross-linkage of hydroxyapatite/gelatin nanocomposite using imide-based zero-length cross-linker

Hydroxyapatite [HAp]/Gelatin [GEL] nanocomposite was prepared at 37 and 48 °C through coprecipitation process. The HAp/GEL nanocomposite slurries were cross-linked by imide-based zero-length cross-linking agent such as N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide (EDC) and N-hydroxysuccinimide (NHS). The chemical bond formation and microstructure in HAp/GEL nanocomposite was investigated as a function of cross-linking agents and temperature. The single addition of EDC into the composite slurries resulted in a tougher microstructure in both samples prepared at 37 and 48 °C. However, in the case of the simultaneous addition of EDC and NHS the sample prepared at 48 °C showed a coarse microstructure. These results were consistent with the fact that the chemical reactivity of NHS is degraded at 48 °C whereas the reactivity of EDC increases up to 80 °C.     

Bioactive nanocomposite coatings of collagen/hydroxyapatite on titanium substrates

Collagen/hydroxyapatite (HA) nanocomposite thin films containing 10, 20, and 30 wt.% HA were prepared on commercially pure titanium substrates by the spin coating of their homogeneous sols. All of the nanocomposite coatings having a thickness of ∼7.5 μm exhibited a uniform and dense surface, without any obvious aggregation of the HA particles. A minimum contact angle of 36.5° was obtained at 20 wt.% HA, suggesting that these coatings would exhibit the best hydrophilicity. The in vitro cellular assays revealed that the coating treatment of the Ti substrates favored the adhesion of osteoblast-like cells and significantly enhanced the cell proliferation rate. The cells on the nanocomposite coatings expressed much higher alkaline phosphatase (ALP) levels than those on the uncoated Ti substrates. Increasing the amount of HA resulted in a gradual improvement in the ALP activity. The nanocomposite coatings on Ti substrates also exhibited much better cell proliferation behaviors and osteogenic potentials than the conventional composite coatings with equivalent compositions, demonstrating the greater potential of the former as implant materials for hard tissue engineering.     

Synthesis and characterization of MWCNT/TiO2 /Au nanocomposite for photocatalytic and antimicrobial activity.

A novel combination of titanium oxide (TiO₂)/gold (Au)/multiwalled carbon nanotubes (MWCNTs) nanocomposite (NC) was synthesised by sol– gel method. MWCNT functionalisation by modified Hummers method. TiO₂ /Au nanoparticles (NPs) were synthesised by biological method using Terminalia chebula bark extract. MWCNT/TiO₂ /Au NC samples were characterised by X‐ray diffraction, ultraviolet–visible–diffuse reflectance spectra, microRaman, scanning electron microscopy and high‐resolution‐transmission electron microscopy analyses. The photocatalytic performance of the obtained for NC toward the decomposition of congo‐red and the antimicrobial activity for inhibition of Gram positive (Bacillus subtilis, Streptococcus pneumonia and Staphylococcus aureus), Gram negative (Shigella dysenderiae, Proteus vulgaris and Klebsiella pneumonia) and fungal strains have been evaluated and the results are compared with positive control ampicillin. The metal and metal–oxide NPs have a lower sorption capacity. The herbicidal bond to the tested CNTs by the combination of electron donor–acceptor interactions and hydrogen bonds. In particular, the dispersion of NC and control of sodium borohydride, it has more efficient effect on the photodegradation and antibacterial activity of positive control of ampicillin. The NC material has exhibited maximum photodegradation and antibacterial activity results of zone of inhibition when compared with control samples.Inspec keywords: nanocomposites, nanoparticles, titanium compounds, gold, multi‐wall carbon nanotubes, nanofabrication, sol‐gel processing, catalysis, photodissociation, antibacterial activity, microorganisms, X‐ray diffraction, reflectivity, Raman spectra, ultraviolet spectra, visible spectra, hydrogen bonds, scanning electron microscopy, transmission electron microscopy, dyes, sorption, nanobiotechnologyOther keywords: titanium oxide‐gold‐multiwalled carbon nanotubes nanocomposite, sol‐gel method, photocatalytic activity, antimicrobial activity, MWCNT functionalisation, modified Hummers method, nanoparticles, biological method, Terminalia chebula bark extract, X‐ray diffraction, ultraviolet‐visible‐diffuse reflectance spectra, microRaman spectra, scanning electron microscopy, high‐resolution‐transmission electron microscopy, congo‐red decomposition, Gram positive bacteria, Bacillus subtilis, Streptococcus pneumonia, Staphylococcus aureus, Shigella dysenderiae, Proteus vulgaris, Klebsiella pneumonia, fungal strains, Gram negative bacteria, sorption capacity, herbicidal bond, electron donor‐acceptor interactions, hydrogen bonds, sodium borohydride, photodegradation, metal‐oxide nanoparticles, C‐TiO₂ ‐Au     

Novel biomimetic hydroxyapatite/alginate nanocomposite fibrous scaffolds for bone tissue regeneration

Hydroxyapatite/alginate nanocomposite fibrous scaffolds were fabricated via electrospinning and a novel in situ synthesis of hydroxyapatite (HAp) that mimics mineralized collagen fibrils in bone tissue. Poorly crystalline HAp nanocrystals, as confirmed by X-ray diffractometer peak approximately at 2θ = 32° and Fourier transform infrared spectroscopy spectrum with double split bands of PO₄(v ₄) at 564 and 602 cm^?1, were induced to nucleate and grow at the [–COO^?]–Ca²⁺–[–COO^?] linkage sites on electrospun alginate nanofibers impregnated with PO₄ ^3? ions. This novel process resulted in a uniform deposition of HAp nanocrystals on the nanofibers, overcoming the severe agglomeration of HAp nanoparticles processed by the conventional mechanical blending/electrospinning method. Preliminary in vitro cell study showed that rat calvarial osteoblasts attached more stably on the surface of the HAp/alginate scaffolds than on the pure alginate scaffold. In general, the osteoblasts were stretched and elongated into a spindle-shape on the HAp/alginate scaffolds, whereas the cells had a round-shaped morphology on the alginate scaffold. The unique nanofibrous topography combined with the hybridization of HAp and alginate can be advantageous in bone tissue regenerative medicine applications.     

Biodegradable polylactide/hydroxyapatite nanocomposite foam scaffolds for bone tissue engineering applications

Supercritical carbon dioxide processing of poly-L-lactide (PLLA)/hydroxyapatite (nHA) nanocomposites was investigated as a means to prepare foams suitable as scaffolds in bone tissue engineering applications. For given foaming parameters, addition of nHA to the PLLA gave reduced cell sizes and improved homogeneity in the size distribution, but did not significantly affect the degree of crystallinity, which remained of the order of 50 wt% in all the foams. The compressive modulus and strength were primarily influenced by the porosity and there was no significant reinforcement of the matrix by the nHA. The mechanical properties of the foams were nevertheless comparable with those of trabecular bone, and by adjusting the saturation pressure and depressurization rate it was possible to generate porosities of about 85 %, an interconnected morphology and cell diameters in the range 200-400 μm from PLLA containing 4.17 vol% nHA, satisfying established geometrical requirements for bone replacement scaffolds.     

Synthesis and characterization of hydroxyapatite/chitosan nanocomposite materials for medical engineering applications

Incorporation of hydroxyapatite (HA) with organic polymer in favor of composites would be used in biomaterial engineering. According to prior researches, because of its chemical similarity to natural bone and dental, this product could improve bioactivity and bone bonding ability. In this research, nano-hydroxyapatite/chitosan composite material was prepared via in situ Hybridization route. The surface chemical characterization on the nanocomposite was evaluated by Fourier transformed infrared (FTIR) and X-ray diffraction (XRD). Surface topography, roughness and morphology of the samples were observed by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The characterization results confirmed homogeneity, interaction and integration between the HA and chitosan matrix. It was indicated that composite samples consist of homogeneous aggregations around 40–100 nm, in which many HA nanocrystals align along the chitosan molecules. HA grain gradually decreased in size when amount of chitosan increased from 0 to 6 g into 100 cc solution. It can be seen that by increasing chitosan, the aggregation of nanoparticles enhance and subsequently, improve the expected compatibility among HA filler and chitosan matrix. Furthermore, the mechanical compressive testing indicated that the synthesized composites have acceptable mechanical behavior for tissue substitution. The mechanistic of the biodegradable nanocomposite systems, their preparation and characterization for medical usage are strongly discussed.     

Biomimetic design of a bacterial cellulose/hydroxyapatite nanocomposite for bone healing applications

This study describes the design and synthesis of bacterial cellulose/hydroxyapatite nanocomposites for bone healing applications using a biomimetic approach. Bacterial cellulose (BC) with various surface morphologies (pellicles and tubes) was negatively charged by the adsorption of carboxymethyl cellulose (CMC) to initiate nucleation of calcium-deficient hydroxyapatite (cdHAp). The cdHAp was grown in vitro via dynamic simulated body fluid (SBF) treatments over a one week period. Characterization of the mineralized samples was done with X-ray Photoelectron Spectroscopy (XPS) and Field Emission Scanning Electron Microscopy (FESEM) with Energy Dispersive Spectroscopy (EDS). The amount of cdHAp observed varied among different samples. XPS demonstrated that the atomic presence of calcium and phosphorus ranged from 0.44 at.% to 7.71 at.% Ca and 0.27 at.% to 11.18 at.% P. The Ca/P overall ratio ranged from 1.22 to 1.92. FESEM images showed that the cdHAp crystal size increased with increasing nanocellulose fibril density. To determine the viability of the scaffolds in vitro, the morphology and differentiation of osteoprogenitor cells was analyzed using fluorescence microscopy and alkaline phosphatase gene expression. The presence of cdHAp crystals on BC surfaces resulted in increased cell attachment.     

Fluoridated hydroxyapatite/titanium dioxide nanocomposite coating fabricated by a modified electrochemical deposition

Fluoridated hydroxyapatite/titanium dioxide nanocomposite coating was successfully fabricated by a modified electrochemical deposition technique. F⁻ ions, nanoscaled TiO₂ particles and 6% H₂O₂ was added into the electrolyte, and ultrasonication was also performed to prepare this nanocomposite coating. The microstructure, phase composition, dissolution rate, bonding strength and in vitro cellular responses of the composite coating were investigated. The results show that the composite coating was uniform and dense owing to the effects of H₂O₂ and ultrasonication. The thickness of the composite coating was ~5 μm and scanning electron microscopy revealed that nanoscaled TiO₂ particles were imbedded uniformly between FHA crystals. The addition of F⁻ and TiO₂ reduced the crystallite size and increased the crystallinity of HA in FHA/TiO₂ composite coating. In addition, the composite coating shows higher bonding strength and lower dissolution rate than pure HA coating, and the in vitro bioactivity of FHA/TiO₂ composite coating was not affected as compared with pure HA coating.     

Synthesis of AgBr/ZnO nanocomposite with visible light-driven photocatalytic activity

AgBr/ZnO nanocomposite was synthesized via chemical precipitation from pure ZnO nanowires, AgNO₃, and NaBr. Inductively coupled plasma optical emission spectroscopy, X-ray diffraction, and high resolution transmission electron microscopy results confirmed the forming of AgBr/ZnO nanocomposite. High resolution transmission electron microscopy results of the as-synthesized AgBr/ZnO nanocomposite revealed that AgBr nanoparticles were attached to the surface of ZnO nanowires. UV-vis diffuse reflectance spectra of both pure ZnO and AgBr/ZnO nanocomposite displayed a band gap edge at about 350-380 nm. However, compared with pure ZnO, an additional broad tail from approximately 400 nm to 700 nm appeared in the UV-vis diffuse reflectance spectrum of AgBr/ZnO nanocomposite. The photocatalytic studies indicated that the as-synthesized AgBr/ZnO nanocomposite was a kind of promising photocatalyst in remediation of water polluted by some chemically stable azo dyes under visible light.     

Electrophoretic-deposited novel ternary silk fibroin/graphene oxide/hydroxyapatite nanocomposite coatings on titanium substrate for orthopedic applications

The combination of graphene oxide (GO) with robust mechanical property, silk fibroin (SF) with fascinating biological effects and hydroxyapatite (HA) with superior osteogenic activity is a competitive approach to make novel coatings for orthopedic applications. Herein, the feasibility of depositing ternary SF/GO/HA nanocomposite coatings on Ti substrate was firstly verified by exploiting electrophoretic nanotechnology, with SF being used as both a charging additive and a dispersion agent. The surface morphology, microstructure and composition, in vitro hemocompatibility and in vitro cytocompatibility of the resulting coatings were investigated by SEM, Raman, FTIR spectra and biocompatibility tests. Results demonstrated that GO, HA and SF could be co-deposited with a uniform, smooth thin-film morphology. The hemolysis rate analysis and the platelet adhesion test indicated good blood compatibility of the coatings. The human osteosarcoma MG63 cells displayed well adhesion and proliferation behaviors on the prepared coatings, with enhanced ALP activities. The present study suggested that SF/GO/HA nanocomposite coatings could be a promising candidate for the surface functionalization of biomaterials, especially as orthopedic implant coating.     

Controlled growth and investigations on the morphology and mechanical properties of hydroxyapatite/titania nanocomposite thin films

In this paper, the focus is on understanding the properties of nanocomposite hydroxyapatite (HAp)/titania (TiO₂) thin films with respect to TiO₂ concentration. HAp/TiO₂ nanostructured composite thin films with different TiO₂ concentrations were successfully fabricated by a simple sol–gel dip coating method. Highly stable HAp and TiO₂ sols were prepared prior to the formation of nanocomposite thin films. The coatings were performed under controlled dipping and heat treatment processes. Phase pure HAp and TiO₂ were well developed in the nanocomposite after the heat treatment and this was confirmed by XRD. The SEM and AFM analyses of HAp/TiO₂ nanocomposite coatings show the variation in the morphology as a consequence different TiO₂ concentration. This shows a reduction in the particle size to nanoscale due to the addition of TiO₂. The mechanical strength of the coating also increased upon the addition of TiO₂ as determined by nanoindentation. The composite thin films with 50 and 80 vol.% of TiO₂ show good mechanical strength when compared to other concentrations of TiO₂.     

Biocide activity of diatom-silver nanocomposite

Diatom-nAg composites containing 1 wt.% of metallic silver nanoparticles (≤ 20 nm) have been obtained by a colloidal route and chemical reduction. This nanostructured powder has proved to be a selective green inorganic biocide which reduces the starting concentrations of Escherichia coli and Micrococcus luteus cultures by at least 5 orders of magnitude, while completely inactive against yeast. Diatom-nAg can be considered as a selective inorganic biocide particularly suitable for the food and pharmacological sectors. The silver nanoparticles are released from the diatom surface to the liquid media in a controlled manner, reaching a concentration (< 11 ppm) far below the toxicity limit for human cells.     

Hydrothermal synthesis of SnO2/SnS2 nanocomposite with high visible light-driven photocatalytic activity

SnO₂/SnS₂ nanocomposite with a heterojunction structure (that is, SnO₂ nanoparticles-decorated SnS₂ nanoplates) was synthesized via the hydrothermal reaction between SnO₂ nanoparticles and thioacetamide in 5 vol.% acetic acid aqueous solution at 150 °C for 3 h, and characterized by X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy and UV–vis diffuse reflectance spectra. The photocatalytic activity of the hydrothermally synthesized SnO₂/SnS₂ nanocomposite was tested by degrading methyl orange in distilled water under visible light (λ > 420 nm) irradiation. It was found that the hydrothermally synthesized SnO₂/SnS₂ nanocomposite exhibited superior photocatalytic activity to SnO₂ nanoparticles, SnS₂ nanoplates and physically mixed SnO₂/SnS₂ nanocomposite. The heterojunction structure of the hydrothermally synthesized SnO₂/SnS₂ nanocomposite, which can facilitate interfacial electron transfer and reduce the self-agglomeration of two components, was considered to play an important role in achieving its higher photocatalytic activity.     

SiO2/M纳米复合材料的结构及催化性能

采用溶胶-凝胶法和超临界干燥法制备了SiO2/M(Cu,Co)纳米复合材料,对其结构、形貌进行了TEM和比表面分析,并研究了SiO2/M纳米复合材料的催化性能.结果表明,制得的SiO2/M纳米复合材料保留了SiO2气凝胶的纳米网络和高比表面积,金属组份Cu与Co均匀地分散在纳米级SiO2气凝胶骨架中,对CO的氧化反应以及CO-NO反应均表现出高的催化活性.