Three-dimensional printing of a β-tricalcium phosphate scaffold with dual bioactivities for bone repair

β-Tricalcium phosphate (β-TCP) had been widely used in the field of bone defect repair because of its osteoconduction and osteoinduction properties. However, for critical-sized bone defects, β-TCP scaffolds need to be functionalised to enhance osteoinduction and antibacterial activity. In this study, we proposed a protocol for mimicking a mussel adhesion mechanism to immobilise bone morphoprotein 2 mimetic peptide (BMP2-MP) and Ornithodoros savignyi (OS) on a three-dimensionally printed β-TCP scaffold. BMP2-MP and the OS polypeptides containing the YKYKY tail were converted into 3,4‐dihydroxyphenylalanine (DOPA) molecules via hydroxylase. The surface morphology and phase composition of the different scaffolds were analysed via scanning electron microscopy and X-ray diffraction. In addition, the binding activity of BMP2-MP and OS containing the DOPA tail to the scaffold were evaluated. The antibacterial activity of the different scaffolds was studied in vitro by performing bacteriostatic experiments against Escherichia coli and Staphylococcus aureus. The osteoinduction capability of the different scaffolds was evaluated by detecting osteogenesis-associated genes via quantitative polymerase chain reaction and by determining alkaline phosphatase expression levels. Our results demonstrated that introduction of the DOPA tail enhanced the binding capability of BMP2-MP and OS with the β-TCP scaffold, thereby enhancing the antibacterial and osteoinduction capabilities of the scaffold. A scaffold with strong antibacterial and osteoinduction capability will have good application prospects in the field of critical-sized bone defect repair.     

Indirect fabrication of hydroxyapatite/β-tricalcium phosphate scaffold for osseous tissue formation using additive manufacturing technology

Patient specific HA/β-TCP scaffold were fabricated using an indirect fabrication approach which involves the application of rapid prototyping technology. β-TCP powder with 10, 20 and 30 % HA concentrations were analyzed for different sintering temperatures. Scaffolds were evaluated by Scanning Electron Microscopy, X-ray diffraction, compression tests, Fourier transform infrared spectroscopy and cytotoxicity tests using human osteosarcoma cell line. Results include HA/β-TCP scaffold porosity, volumetric shrinkage, mechanical properties, bonding, structural phase change and cytotoxicity.     

DLP 3D printing porous β-tricalcium phosphate scaffold by the use of acrylate/ceramic composite slurry

Digital light processing (DLP) 3D printing has been utilized to fabricate controlled porous β-tricalcium phosphate (β-TCP) scaffolds, which promote cell adhesion and angiogenesis during bone regeneration. However, the current limitation of DLP 3D printing for the fabrication of β-TCP scaffold is how to prepare a low viscosity ceramic slurry and remove the toxicity of residual non-polymerized slurry. The present study has developed a low viscosity ceramic slurry system by mixing β-TCP with photosensitive acrylate resin, and the viscosity of slurry is about 3 Pa s and the solid content of β-TCP can be as high as 60 wt%. After optimizing the ratio of slurry, printing, degreasing and sintering processes, the maximum compressive strength of the DLP printed scaffolds reaches up to 9.89 MPa, while the porosity keeps ca. 40%. According to the proliferation of cells, it confirms the preserved biocompatibility of DLP-fabricated β-TCP scaffolds. These porous scaffolds made by DLP 3D printing technology is of great significance for bone regeneration, and will also help to expand the application of DLP technology in biomedical field.     

Preparation and characterization of iron/β-tricalcium phosphate bio-cermets for load-bearing bone substitutes

Ceramic-metal composite materials, namely cermets, are provided with characteristics of both ceramic and metal. Herein, for the first time bio-cermets based on β-tricalcium phosphate (β-TCP) bioceramic with biodegradable iron being reinforcement phase, were fabricated using the powder metallurgic method. The phase composition, microstructure, mechanical properties and in vitro cell behaviors of bio-cermets were investigated. The results revealed that atomic diffusion occurred between the iron and β-TCP matrix during the sintering process. The bio-cermets attained remarkable increase in fracture toughness (1.16–1.55 MPa m^1/2) compared to the β-TCP bioceramic (0.54 MPa m^1/2). The bio-cermets with 10 vol% iron showed the highest compressive strength (640 MPa), significantly higher than that of plain β-TCP bioceramic (285 MPa). The in vitro cell behaviors test indicated that the bio-cermets did not showed any sign of toxicity; the iron ions released from bio-cermets up-regulated bone-related gene expression of bone mesenchymal stem cells. The bio-cermets developed in this study represent potential bone substitutes for application in the load-bearing bone defects.     

Biphasic calcium phosphate (BCP) macroporous scaffold with different ratios of HA/β-TCP by combination of gel casting and polymer sponge methods

Abstract

Open and interconnected porous scaffolds were prepared with various ratios of hydroxyapatite (HA)/β-tricalcium phosphate by a combination of gel casting and polymer sponge methods to improve the mechanical properties and structure. The scaffolds were prepared using slurries containing 50 vol.-% of ceramic powders and sintered at 1100°C for 2 h. Thermogravimetric analysis result shows that the proper temperature to burn out organic materials and polyurethane foams is 600°C. The compressive strength was between 5·3 and 8·4 MPa. Field emission scanning electron microscope shows an open, relatively uniform and large interconnected porous structure with pore size ranging between 150 and 400 μm. X-ray diffraction and Brunauer–Emmett–Teller methods were employed to determine the microstructural crystallite and surface area respectively. The results show that the compressive strength of scaffolds increased with the increase in HA concentration. The reason can be explained by the increasing pore wall thickness and density in scaffolds.     

Evaluation of hydroxyapatite and β-tri calcium phosphate microplasma spray coated pin intra-medullary for bone repair in a rabbit model

Here we report a comparative study of the healing kinetics of surgically created artificial defects in the tibia of New Zealand white rabbits. Comparison of the healing kinetics was made for uncoated conventional SS316L intramedullary pins, and the same pins with microplasma sprayed (MIPS) pure hydroxyapatite (HAp) and beta-tri calcium phosphate (β-TCP) coatings. After thorough material characterizations including XRD, FTIR, SEM, etc., MIPS coated pins were implanted to such animals. Serum biochemistry, radiology and fluorochrome labelling were used to evaluate the comparative healing kinetics of these implants in vivo. In comparison to those of the uncoated pins, the pins coated with both MIPS HAp and β-TCP showed significant increment of alkaline phosphatase up to 15th postoperative day, insignificant changes in serum phosphorus and calcium with uneventful healing of bone defect. There was development of Havarsian canals and well-defined peripherally placed osteoblasts along with evidence of angiogenesis and comparatively more new bone formation in the defect site. On a comparative scale, the performance of the β-TCP coated intramedullary pins was much better than that of the pure HAp coated pins than the uncoated intramedullary pins.     

The impact of molecular weight on microstructure and charge transport in semicrystalline polymer semiconductors–poly(3-hexylthiophene), a model study

Electronic properties of organic semiconductors are often critically dependent upon their ability to order from the molecular level to the macro-scale, as is true for many other materials attributes of macromolecular matter such as mechanical characteristics. Therefore, understanding of the molecular assembly process and the resulting solid-state short- and long-range order is critical to further advance the field of organic electronics. Here, we will discuss the structure development as a function of molecular weight in thin films of a model conjugated polymer, poly(3-hexylthiophene) (P3HT), when processed from solution and the melt. While focus is on the microstructural manipulation and characterization, we also treat the influence of molecular arrangement and order on electronic processes such as charge transport and show, based on classical polymer science arguments, how accounting for the structural complexity of polymers can provide a basis for establishing relevant processing/structure/property-interrelationships to explain some of their electronic features. Such relationships can assist with the design of new materials and definition of processing protocols that account for the molecular length, chain rigidity and propensity to order of a given system.     

Production and study of in vitro behaviour of monolithic α-tricalcium phosphate based ceramics in the system Ca3(PO4)2–Ca2SiO4

In this work a new kind of α-tricalcium phosphate (α-Ca₃(PO₄)₂) doped with dicalcium silicate (Ca₂SiO₄) ceramic materials, with compositions lying in the field of the Ca₃(PO₄)₂ solid solution in the system Ca₃(PO₄)₂–Ca₂SiO₄, were obtained. The properties of the sintered ceramics were discussed in detail as well as some in vitro relevant properties for bone repairing. Crystalline α-Ca₃(PO₄)₂ solid solution (α-TCPss) was the only phase in the ceramics containing from 1 wt% to 4 wt% of Ca₂SiO₄. The release of ionic Si in simulated body fluid increased with the content of Ca₂SiO₄ and favoured α-Ca₃(PO₄)₂ surface transformation. In addition, cell attachment test showed that the α-TCPss supported the mesenchymal stem cells adhesion and spreading, and the cells established close contact with the ceramics after 24 h of culture. According to the results, the investigated α-TCPss ceramics possesses good bioactivity, biocompatibility and mechanical properties, and might be a promising bone implant material.     

Parallel screening of Cu/CeO2/γ-Al2O3 catalysts for steam reforming of methanol in a 10-channel micro-structured reactor

Steam reforming of methanol (SRM) was investigated over Cu/CeO₂/γ-Al₂O₃ catalysts with different compositions in a parallelized 10-channel micro-structured reactor. The catalytic activity was found to be strongly dependent on the copper loading. The parallel screening result was tentatively discussed with surface analysis characterization results and previous proposals. A reaction mechanism is proposed to rationalize the catalytic activity data and characteristics of the catalysts, which supposes that the copper/ceria interfacial area (partially oxidized copper nanoparticle and defective ceria) is the active site for SRM. The oxygen reverse spillover from ceria to copper is suggested to be involved in the catalysis cycle.     

A facile preparation of 3D flower-shaped Ni/Al-LDHs covered by β-Ni(OH)2 nanoplates as superior material for high power application

In the present study, we propose a novel electrode material of β-nickel hydroxide covering nickel/aluminum layered double hydroxides via a facile complexation-precipitation method. The as-obtained materials with 3-dimensional nanostructures are further utilized as highly capable electrode material in nickel-metal hydride batteries. The electrochemical test results demonstrated the β-nickel hydroxide covering nickel/aluminum-layered double hydroxides with 28% of β-nickel hydroxide provided a superior specific capacity value of 452 mA·h·g^-1 in a current density of 5 A·g^-1 using 6 M KOH as electrolyte as compared with other materials. In addition, the optimized sample displays an outstanding cyclic stability along with a huge specific capacity value of 320 mAh·g^-1, and very small decay rate of 3.3% at 50 A·g^-1 after 3000 cycles of charge/discharge test. These indicate that the newly designed material with nanostructures not only provides an efficient contact interface between electrolyte and active species and facilitates the transport of electrons and ions, but also protects the 3-dimensional nickel/aluminum layered double hydroxides, achieving a high specific capacity, fast redox reaction and excellent long-term cyclic stability. Therefore, the β-nickel hydroxide covering nickel/aluminum layered double hydroxides with superior electrochemical performance is predictable to be a gifted electrode material in nickel-metal hydride batteries.     

Electrochemical characterization of the Pt/β′′–Al2O3 system under conditions of in situ electrochemical modification of catalytic activity for propane combustion

Linear sweep and cyclic voltammetry were used for electrochemical characterization of the Pt/sodium-β′′-Al₂O₃ system and investigation of the phases formed upon electrochemical pumping of sodium ions to the Pt catalyst-electrode under conditions of propane combustion or under mixtures of O₂ or CO₂ with helium, at temperatures between 320 and 480 °C. The number, position and magnitude of the peaks in the obtained voltammograms were found to depend on gas phase composition, temperature, and pre-scan (initial polarization) conditions. The results showed that under conditions of propane combustion more than one sodium phases can be formed as a result of electrochemical pumping of sodium ions to the Pt catalyst. The related electrochemical reactions and the identity of these sodium phases, which correspond mainly to carbonate or bicarbonate phases but also to oxide phases, are discussed on the basis of the obtained results and those of former studies.     

A novel “plane-line-plane” nanostructure of the sandwich-like CNTs@SnO2/Ti3C2Tx 3D nanocomposite as a promising anode for lithium-ion batteries

As one of the novel two-dimensional metal carbides, Ti₃C₂T_x has received intense attention for lithium-ion batteries. However, Ti₃C₂T_x has low intrinsic capacity due to the fact that the surface functionalization of F and OH blocks Li ion transport. Herein a novel “plane-line-plane” three-dimensional (3D) nanostructure is designed and created by introducing the carbon nanotubes (CNTs) and SnO₂ nanoparticles to Ti₃C₂T_x via a simple hydrothermal method. Due to the capacitance contribution of SnO₂ as well as the buffer role of CNTs, the as-fabricated sandwich-like CNTs@SnO₂/Ti₃C₂T_x nanocomposite shows high lithium ion storage capabilities, excellent rate capability and superior cyclic stability. The galvanostatic electrochemical measurements indicate that the nanocomposite exhibits a superior capacity of 604.1 mAh g^?1 at 0.05?A?g^?1, which is higher than that of raw Ti₃C₂T_x (404.9 mAh g^?1). Even at 3?A?g^?1, it retains a stable capacity (91.7 mAh g^?1). This capacity is almost 5.6 times higher than that of Ti₃C₂T_x (16.6 mAh g^?1) and 58 times higher than that of SnO₂/Ti₃C₂T_x (1.6 mAh g^?1). Additionally, the capacity of CNTs@SnO₂/Ti₃C₂T_x for the 50th cycle is 180.1 mAh g^?1 at 0.5?A?g^?1, also higher than that of Ti₃C₂T_x (117.2 mAh g^?1) and SnO₂/Ti₃C₂T_x (65.8 mAh g^?1), respectively.     

Preparation of Pd/γ-Al2O3/nickel foam monolithic catalyst and its performance for selective hydrogenation in a rotating packed bed reactor

Selective hydrogenation plays an important role in chemical industries,yet its selectivity is usually lim-ited by the mass transfer.In this work,the enhanced hydrogenation selectivity was achieved in a rotating packed bed (RPB) reactor with excellent mass transfer efficiency.Aiming to be used under the centrifugal filed,a monolithic catalyst Pd/γ-Al2O3/nickel foam suiting for the shape and size of the rotor of RPB reac-tor was prepared by the electrophoretic deposition method.The mechanical strength of the catalyst can meet the requirement of high centrifugal force in the RPB.The hydrogenation selectivity in the RPB reac-tor using the 3-methyl-1-pentyn-3-ol hydrogenation system was 3-8 times higher than that in a stirred tank reactor under similar conditions.This work proves the feasibility of intensifying the selectivity of hydrogenation process in the RPB reactor.     

La0.8Sr0.2Co0.3Fe0.7O3−δ as a novel candidate coating material for the positive current collector in sodium sulfur battery

The corrosion behaviors of perovskite La_0.8Sr_0.2Co_0.3Fe_0.7O_3−δ (LSCF) in the sodium tetrasulfide melt have been studied to demonstrate its possibility to be used as a coating material for the positive current collector in the sodium sulfur battery (Na/S). The electrochemical techniques including potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) are applied in the study. The results demonstrate that the corrosion process of the LSCF in sodium tetrasulfide melt is activation controlled. The corrosion current density of the LSCF is approximate 10 times smaller than that of the 316L stainless steel. Two compact corrosion layers which may act as a stable barrier retarding the corrosion process have formed on the surface of LSCF after immersed for 130 days. The promising results suggest that LSCF exhibits high corrosion resistance against molten sodium tetrasulfide and may be an appropriate candidate coating material for the positive current collector in Na/S battery.     

Multiscale investigation on fatigue properties and damage of a 3D braided SiC/SiC + PyC/SiC composites in the full stress range at 1300 °C

Monotonic tensile and fatigue tests of a SiC/SiC composites were conducted at 1300 °C in the full stress range. The macroscopic behaviors were studied based on the strain data. The mesoscopic morphology was observed by X-ray computed tomography, and the microanalysis was conducted using SEM, EDS and XRD. Besides, the interfacial debonding strength (IDS) were measured by nano-indenter. The results reveal that the fatigue behaviors can be divided into three zones. The inelastic strains accumulation and stiffness reduction can be observed in all three zones due to matrix cracking, interface damage, and failure of fibers. The fatigue life is long in the run-out zone because the maximum stress is lower than the proportional limit stress (PLS). In the stress-insensitive zone, the fracture depends on high-temperature and oxidation effects. The failure in the stress-sensitive zone is dominated by the fiber strength. The interface behaviors greatly affect the fatigue life above the PLS.     

La1−xSrxFeO3−δ perovskites as redox materials for application in a membrane reactor for simultaneous production of pure hydrogen and synthesis gas

This work reports on the preparation and characterization of perovskitic materials with the general formula La_1−xSr_xFeO₃ (x = 0, 0.3, 0.7, 1) for application in a dense mixed conducting membrane reactor process for simultaneous production of synthesis gas and pure hydrogen. Thermogravimetric experiments indicated that the materials are able to loose and uptake reversibly oxygen from their lattice up to 0.2 oxygen atoms per “mole” for SrFeO₃ with x = 1 at 1000 °C. The capability of the prepared powders to convert CH₄ during the reduction step, in order to produce synthesis gas, as well as their capability to dissociate water during the oxidation step, in order to produce hydrogen were evaluated by pulse reaction experiments in a fixed bed pulse reactor. The high sintering temperatures (1100-1300 °C) required for the densification of the membrane materials result in decreased methane conversion and H₂ yields during the reduction step compared to the corresponding values obtained with the perovskite powders calcined at 1000 °C. Addition of small quantities of NiO, by simple mechanical mixing, to the perovskites after their sintering at high temperatures, increases substantially both their methane decomposition reactivity, their selectivity towards CO and H₂ and their water splitting activity. Maximum H₂ yield during the reduction step is achieved with the La_0.7Sr_0.3FeO₃ sample mixed with 5% NiO and is 80% of the theoretically expected H₂, based on complete methane decomposition. In the oxidation - water splitting step, 912 μmol H₂ per gr solid are produced with the La_0.3Sr_0.7FeO₃ sample mixed with 5% NiO. The experimental results of this work can be equally well applied for the “chemical-looping reforming” process since they concern using the lattice oxygen of the perovskite oxides for methane partial oxidation to syngas, in the absence of molecular oxygen, and subsequent oxidation of the solid.     

A missing oxidation-state level in the family of polyoxo(azide)octadecavanadate(IV/V) clusters: Synthesis,structure and antitumoural properties of [VIV11VV7O44(N3)]10 − in a sodium containing-3D architecture

The missing V^IV₁₁V^V₇ oxidation-state member of the polyoxooctadecavanadate(IV/V) — azide family of inorganic host-guest systems has been incorporated in a Na^I-containing 3D architecture; the complex shows remarkable inhibition properties on human platelet aggregation and antitumoural activity against cancer cell lines.     

Inhibiting HDS and HYD reactions with quinoline on Co(Ni)–PMo(W)/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts: Effect of active phase composition on stability in the hydrotreatment of a model petroleum raw material

Со(Ni)–PMo(W)/Al₂O₃ catalysts are prepared using Keggin heteropoly acids H₃PMo(W)₁₂O₄₀ and cobalt (nickel) citrate. The physicochemical properties of the catalysts are studied via low-temperature nitrogen adsorption, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy. Their catalytic properties are determined in the hydrotreatment of a model raw material containing dibenzothiophene, naphthalene, and different amounts of quinoline (up to 1000 ppm of nitrogen), and in the hydrotreatment of a straight-run diesel fraction and vacuum gas oil. The composition of Со(Ni)–PMo(W)/Al₂O₃ catalysts plays an important role in the hydrotreatment of a complex hydrocarbon raw material. Ni–PW/Al₂O₃ catalyst is more resistant to organonitrogen inhibitors than Ni(Co)–PMo/Al₂O₃ samples with more reactive active sites. Ni–PW/Al₂O₃ catalyst provides the greatest depth of conversion for sulfur- and nitrogen-containing compounds and polycyclic aromatic hydrocarbons in the hydrotreatment of vacuum gas oil.