Interconnected Spherical Pores Research Articles

Cells Resident to Precision Templated 40-µm Pore Scaffolds Generate Small Extracellular Vesicles that Affect CD4+ T Cell Phenotypes Through Regulatory TLR4 Signaling.

Precision porous templated scaffolds (PTS) are a hydrogel construct of uniformly sized interconnected spherical pores that induce a pro-healing response (reducing the foreign body reaction, FBR) exclusively when the pores are 30-40µm in diameter. Our previous work demonstrated the necessity of Tregs in the maintenance of PTS pore size specific differences in CD4+ T cell phenotype. Work here characterizes the role of Tregs in the responses to implanted 40µm and 100µm PTS using WT and FoxP3+ cell (Treg) depleted mice. Proteomic analyses indicate that integrin signaling, monocytes/macrophages, cytoskeletal remodeling, inflammatory cues, and vesicule endocytosis may participate in Treg activation and the CD4+ T cell equilibrium modulated by PTS resident cell-derived small extracellular vesicles (sEVs). The role of MyD88-dependent and MyD88-independent TLR4 activation in PTS cell-derived sEV-to-T cell signaling is quantified by treating WT, TLR4ko, and MyD88ko splenic T cells with PTS cell-derived sEVs. STAT3 and mTOR are identified as mechanisms for further study for pore-size dependent PTS cell-derived sEV-to-T cell signaling. STATEMENT OF SIGNIFICANCE: Unique cell populations colonizing only within 40µm pore size PTS generate sEVs that resolve inflammation by modifying CD4+ T cell phenotypes through TLR4 signaling.

Fabrication of hyperbranched polyamidoamine immobilized mesocellular siliceous foam for rapid decontamination of lead(II) from aqueous solution

Developing of adsorbents with merits of higher adsorption capacity and quicker adsorption equilibrium through facile method merits more attention. Generally, large specific surface area porous adsorbent coupled with multi functional groups is a wise option. In the current work, a feasible protocol of preparing efficient adsorbent toward Pb2+ was established via integrating amino abundant hyperbranched polyamidoamine and bimodal pore structured mesocellular siliceous foam. The polyamidoamine was synthesized through a vacuum thermo polymerization method by gradually elevating temperature. The uniform spherical mesocellular siliceous foam substrate was prepared via inorganic salt-assisted soft-template method, and the pore structure and particle morphology were adjusted through post hydrothermal treatment. The obtained hyperbranched polyamidoamine immobilized mesocellular siliceous foam was characterized using FT-IR, SAXS, BET, SEM, TEM, TGA and zeta potential measurement techniques. Large specific surface area, unique bimodal pore structure with interconnected spherical and window pore and ultra large pore diameter rendered the adsorbent high adsorption capacity and efficient elimination. Batch experiment results elucidated that various operating parameters including pH, contact time, initial Pb2+ concentration, temperature and ionic strength deemed to be at play in adsorption behavior. The measured experimental maximum adsorption capacity at 298.15 K was 142.87 mg·g−1. The equilibrium data fitted well by pseudo second order kinetic model unveiled that the rate determining step might be chemical adsorption. The adsorption behavior was found to more suitable described with Langmuir isotherm model, implying the formation of adsorbate monolayer, and thus a maximum adsorption capacity of 315.46 mg·g−1 at 298.15 K was estimated. An underlying spontaneous entropy increased endothermic nature of adsorption of Pb2+ by the as-prepared adsorbent was conceived through adsorption thermodynamics study. Furthermore, a possible adsorption mechanism of comprehensive interaction of chemical chelation and ion exchange was proposed. This study supports the prospect that hyperbranched polyamidoamine immobilized mesocellular siliceous foam can serve as a candidate for efficiently removing Pb2+ from aqueous solution.

Preparation of an Ordered Nanoporous Silicone-based Material Using Silica Colloidal Crystals as a Hard Template

An ordered nanoporous silicone-based material with an inverse opal structure consisting of interconnected spherical pores was prepared by the thiol-ene reaction of linear and cyclic organosiloxanes...

Hybrid Three-Dimensional-Printed Ear Tissue Scaffold With Autologous Cartilage Mitigates Soft Tissue Complications.

To analyze the use of highly translatable three-dimensional (3D)-printed auricular scaffolds with and without novel cartilage tissue inserts in a rodent model. Preclinical rodent animal model. This prospective study assessed a single-stage 3D-printed auricular bioscaffold with or without porcine cartilage tissue inserts in an athymic rodent model. Digital Imaging and Communications in Medicine computed tomography images of a human auricle were segmented to create an external anatomic envelope filled with orthogonally interconnected spherical pores. Scaffolds with and without tissue inset sites were 3D printed by laser sintering bioresorbable polycaprolactone, then implanted subcutaneously in five rats for each group. Ten athymic rats were studied to a goal of 24 weeks postoperatively. Precise anatomic similarity and scaffold integrity were maintained in both scaffold conditions throughout experimentation with grossly visible tissue ingrowth and angiogenesis upon explantation. Cartilage-seeded scaffolds had relatively lower rates of nonsurgical site complications compared to unseeded scaffolds with relatively increased surgical site ulceration, though neither met statistical significance. Histology revealed robust soft tissue infiltration and vascularization in both seeded and unseeded scaffolds, and demonstrated impressive maintenance of viable cartilage in cartilage-seeded scaffolds. Radiology confirmed soft tissue infiltration in all scaffolds, and biomechanical modeling suggested amelioration of stress in scaffolds implanted with cartilage. A hybrid approach incorporating cartilage insets into 3D-printed bioscaffolds suggests enhanced clinical and histological outcomes. These data demonstrate the potential to integrate point-of-care tissue engineering techniques into 3D printing to generate alternatives to current reconstructive surgery techniques and avoid the demands of traditional tissue engineering. NA Laryngoscope, 131:1008-1015, 2021.

Fabrication of highly porous merwinite scaffold using the space holder method

In this study, for the first time, the space holder method was used to fabricate a 3D macroporous nanostructured merwinite scaffold with highly interconnected spherical pores. The nanostructured merwinite powders were prepared by the sol-gel method and an optimal calcination cycle was ascertained. The average values of true and apparent porosities of the prepared scaffolds calculated in the range 85–81% and 80–74%, respectively, while the macropore sizes are determined in the range of 400–600 μm. The compressive strength of the prepared scaffold was obtained to be about 0.18–0.29 MPa. Immersion testing in simulated body fluid proved the appropriate bioactivity and biodegradability of the prepared scaffolds. Our study indicated the merwinite scaffold possessed suitable mechanical strength along with highly porous structure and apatite-formation ability which could be used for bone tissue engineering applications.

Post Polymerisation Hypercrosslinking with Emulsion Templating for Hierarchical and Multi-Level Porous Polymers

Porosity in polymers and polymeric materials adds to their functionality due to achieving the desired tailored characteristics porosity offers, such as improved mass transfer through the material, improved accessibility of reactive sites, reduced overall mass, tunable separation properties, etc. Therefore, applications in many fields, e.g. catalysis, separation, solid phase synthesis, adsorption, sensing, biomedical devices etc., drive the development of polymers with controlled morphology in terms of pore size, shape, interconnectivity and pore size distribution. Of particular interest are polymers with distinct bimodal or hierarchical pore distribution as this enables uses in applications where pore sizes on multiple levels are needed. Emulsion templating can be used for the preparation of polymers with included interconnected spherical pores on the micrometre level while post polymerisation crosslinking adds micro porosity. Combined use of both techniques yields multi-level and hierarchically porous materials with great application potential.

Digitization and image-based structure-properties relationship evaluation of a porous gold micro-electrode

The advantage of using porous materials for biofuel cells and biosensors is their very large internal surface area (where electron exchange takes place) compared to the overall material volume, yielding much larger current densities than on a bare solid electrode of the same size. However, limitations occur because of mass transfer resistance through the pores. We describe here a bottom-up approach to optimize the design of such materials, through the analysis and modeling of their porous structure. Electrodes prepared by replicating stacked Langmuir-Blodgett films, with 1-μm diameter interconnected spherical pores, were studied. Since pore window dimensions are around 100 nm, Focused Ion Beam-Scanning Electron Microscopy (FIB-SEM) has been performed to obtain a 3D reconstruction of the porous medium. Then, a determination of the geometrical characteristics has been achieved through image analysis. The structure of the sphere packing, the shape and size of the connections between spheres, the distances between spheres, the sphere diameters and the specific surface area have been analyzed. The porous medium is close to a face-centered cubic arrangement of spherical pores, but several deviations from ideality are present: missing pores (point defects), stacking errors (dislocations), and incomplete connection between spheres (only 50% of the ideal sphere connections are present). The consequence of such defects on transport is studied through image-based simulations of mass diffusion in the actual porous medium and in similar ideal media.

BTEX Detection Using Piezoelectric Cantilever with Mesocellular Foam Silica Functionalized with Hexamethyldisilazane Sensitive Coating

Introduction Gas detection with gravimetric sensors such as SAW, MEMS, FBAR or QCM is based on a frequency shift when the target specie is (ad)sorbed on a sensitive layer covering the sensor [1]. Sensor’s sensitivity and reliability depend on transducer type and sensitive coating, while selectivity and reversibility are correlated with the sensitive coating’s nature. Research studies are still active on the development of transducers to reduce their cost and power consumption but sensitive coating optimization remains a hot topic for sensitive and selective sensor achievements. Among attractive sensitive coating for gravimetric sensors, high specific area coatings such as CNTs, graphene oxide, microporous/mesoporous materials or MOFs are nowadays majorly studied one [2-3]. Their performances in gas detection can be modified by tuning of pores or surface functionalization. In this work we are interested in applying mesoporous foam silica (MCF), a type of mesoporous silica, as a base for hydrophobic hexamethy-disilazane (HDMS) functionalization, and tested for BTEX detection. Also, low cost printed piezoelectric MEMS cantilevers are used as gravimetric transducers. Piezoelectric cantilever sensor fabrication and tests One type of inorganic mesoporous silica (MPS), mesocellular foam (MCF), is synthesized by using P123 as a template and 1,3,5-trimethylbenzene (TMB) as a pore expander as described in [4]. After the template removal by ethanol extraction, the template removed MCFs are then functionalized by hexamethyldisilazane (HDMS) following protocol described in [5]. For the piezoelectric PZT based transducer fabrication, the process consists of screen-printing of all the layers before a co-sintering at 900°C allowing releasing of the PZT cantilever with Au electrodes. Details on the process can be found in [6]. Photographs of the fired cantilever (~ 3x2x0.08 mm3) are shown Fig. 1. The HDMS functionalized MCF (F_MCF) powder is dispersed in deionized water with the ratio of 100 mg/1 mL before depositing by drop-coating with 1µl of this suspension, followed by a drying . The cantilever is self-actuated and self-readout thanks to piezoelectric effect. Admittance circle B(G) (Fig.3a and Fig. 3b)) shows the piezoelectric effect for the 31 in-plane longitudinal mode. Conductance (G(f)) curve before and after F_MCF deposit (weight ~0.05mg) shows the damping effect due to the additional mass (Fig.3c). Based on the measured dimensions of the cantilever, its density and its resonance, frequency f0 , a theoretical sensitivity S=-f0/2m of ~23Hz/µg is calculated. Finally, the cantilever is tested under gas. A PULL110 vapor generator controls N2 flow (100ml/min) and toluene concentration sent in a home-made PTFE cell. Temperature is controlled during the measurements, and acquisition data (f0 as a function of time) are extracted from G measurement using a polynomial fit described in [6]. Results and Conclusions After washing and drying of the MCF, interconnected spherical pore structure are observed by TEM analysis even after functionalized by HMDS (Fig.2). The analysis results of the N2 adsorption-desorption isotherms of the MCFs are shown in Table 1. Pore and window sizes are not affected by functionalization whereas BET surface areas and BJH pore volumes decrease with the increasing HMDS ratio. Also, after functionalization, as expected, reduction of water adsorbed on the surface of the MCF has been observed by TGA and FTIR analysis, and the optimum HDMS:SiO2 for VOCs detection has been shown to be 0.15 (for benzene detection in fact) [5]. This composition is selected for further experiment under gas. Tests under toluene with F_MCF show a sensitivity of 241 mHz/ppm at f0 ~ 256kHz (Figs. 4a and 3b). The blank cantilever also demonstrates slight sensitivity to toluene (~6 mHz/ppm) (Fig. 4b), attributed to density/viscosity changes of the surrounding fluid and cantilevers’s stiffness. In previous work using polymer PEUT coating, silicon cantilever (0.15x0.15x0.095mm3 ) showed sensitivity of 125mHz/ppm at 350 kHz (out of plane mode), whereas similar printed PZT cantilever of size 8x2x0.08mm3 gave sensitivity of 15mHz/ppm at 70kHz (in plane vibration mode) [7]. Size reduction leading to higher sensitivity because of the increased f0 and lower m, combined with the F_MCF coating clearly improves the sensor performances. Good reversibility is also observed. The noisy curve is mainly due to temperature fluctuation which is not precisely controlled in the cell (±0.2°C). The sensor is indeed sensitive to temperature as shown Fig. 3c. Tests under humidity and benzene are ongoing and temperature compensation with another dummy cantilever fabricated in the same conditions could be implemented.

Pore architecture effects on chondrogenic potential of patient-specific 3-dimensionally printed porous tissue bioscaffolds for auricular tissue engineering

ObjectiveThis study aims to determine the effect of auricular scaffold microarchitecture on chondrogenic potential in an in vivo animal model. MethodsDICOM computed tomography (CT) images of a human auricle were segmented to create an external anatomic envelope. Image-based design was used to generate 1) orthogonally interconnected spherical pores and 2) randomly interspersed pores, and each were repeated in three dimensions to fill the external auricular envelope. These auricular scaffolds were then 3D printed by laser sintering poly-l-caprolactone, seeded with primary porcine auricular chondrocytes in a hyaluronic acid/collagen hydrogel and cultured in a pro-chondrogenic medium. The auricular scaffolds were then implanted subcutaneously in rats and explanted after 4 weeks for analysis with Safranin O and Hematoxylin and Eosin staining. ResultsAuricular constructs with two micropore architectures were rapidly manufactured with high fidelity anatomic appearance. Subcutaneous implantation of the scaffolds resulted in excellent external appearance of both anterior and posterior auricular surfaces. Analysis on explantation showed that the defined, spherical micropore architecture yielded histologic evidence of more robust chondrogenic tissue formation as demonstrated by Safranin O and Hematoxylin and Eosin staining. ConclusionsImage-based computer-aided design and 3D printing offers an exciting new avenue for the tissue-engineered auricle. In early pilot work, creation of spherical micropores within the scaffold architecture appears to impart greater chondrogenicity of the bioscaffold. This advantage could be related to differences in permeability allowing greater cell migration and nutrient flow, differences in surface area allowing different cell aggregation, or a combination of both factors. The ability to design an anatomically correct scaffold that maintains its structural integrity while also promoting auricular cartilage growth represents an important step towards clinical applicability of this new technology.

Finite element multiscale modelling of elastic behavior of cellulose acetate—Graphene oxide nanocomposites, produced using a SC-CO2 assisted technique

This work focuses on the modelling of the mechanical performance of cellulose acetate-graphene oxide nanocomposite membranes, produced by supercritical CO2 assisted phase inversion, using a set of algorithms able to build and integrate two different parametric variational 3D finite element (FE) models. These models simulate micro- and nano-level morphology of the nanocomposite using a multiscale approach. Microlevel is characterized by interconnected spherical pores; whereas, nanolevel is a composites whose filler is formed by graphene oxide sheets. Information about nanocomposite morphology, derived from electron scanning microscopy analyses, was used to build periodic representative volume elements. A numerical-experimental correlation was performed comparing FE model results with the experimental ones obtained by compression tests, at different weight percentages of graphene oxide with respect to the polymer loaded in the membrane. A good approximation of the experimental trend of Young modulus was obtained by FE simulations.

Degradation behavior and compatibility of micro, nanoHA/chitosan scaffolds with interconnected spherical macropores

Hydroxyapatite/Chitosan (HA/CS) composite have significant application in biomedical especially for bone replacement. Inorganic particle shape and size of composite affect the scaffold mechanical property, biological property, and degradation. The aim of this study was to fabricate HA/CS scaffold with good pore connectivity and analyze their biological, degradation properties. Microhydroxyapatite/chitosan (mHA/CS) and nanohydroxyapatite/chitosan (nHA/CS) composite scaffolds with interconnected spherical pore architectures were fabricated. Composite scaffolds structure parameters were analyzed using micro CT. Cell proliferation and morphology were tested and compared between two scaffolds using mouse osteoblastic cell line MC3T3-E1. To research the composite degradation in lysozyme PBS solution, degradation rate and reducing sugar content were tested, and scaffolds morphology were observed by SEM. The results showed that microHA and nanoHA were fabricated by being calcined and synthesis methods, and their infrared spectra are very similar. EDAX composition analysis demonstrated that both of microHA and nanoHA were calcium deficiency HA. Micro-CT results demonstrated the scaffolds had interconnected spherical pores, and the structure parameters were similar. Cell viabilities were significant increased with cultured time, but there were no significant difference between microHA/CS and nanoHA/CS scaffolds. Scaffold structure was gradually destroyed and inorganic composition HA particles are more prominent with degradation time.Significance: (1) Inorganic particle shape and size of composite affect the scaffold mechanical property, biological property, and degradation. NanoHA/CS and microHA/CS scaffolds with good pore connectivity were fabricated and their biological, degradation properties were studied in this manuscript. (2) The scaffold with interconnected porosity construct provides the necessary support for cells to proliferate and maintain their differentiated function, and its architecture related to the structure and morphology of new bone. Polymer scaffolds were fabricated by the technique of compression molding and particulate leaching method, and paraffin microspheres were used as the porogen. (3) MicroHA/CS and nanoHA/CS composite scaffolds are potential materials for use in bone tissue engineering.

Characteristics and Mechanism of Cu(II) Extraction with Polymeric Particles with Interconnected Spherical Pores Impregnated with LIX84-I

Characteristics and Mechanism of Cu(II) Extraction with Polymeric Particles with Interconnected Spherical Pores Impregnated with LIX84-I

Fabrication and characterization nanostructured forsterite foams with high compressive strength, desired porosity and suitable bioactivity for biomedical applications

This work deals with the fabrication and mechanical improvement of nanostructured forsterite foam. Nanostructured forsterite foams were prepared via gelcasting followed by two step sintering. Phase composition, morphology, porosity and compressive strength of the sintered foams were evaluated by X-ray diffractometry, scanning electron microscopy, Archimedes method, and compression tests. In addition, the in vitro bioactivity of forsterite foams was evaluated by soaking the samples in simulated body fluid. Results showed that nanostructured forsterite foams were prepared with maximum compressive strength and elastic modulus of about 7.2 and 271 MPa, respectively. The foams had highly interconnected spherical pores with size in the range of 60–320 μm. Total porosity of the prepared foams was in the range of 79–87 %, which depends on the heat treatment process. During immersion in simulated body fluid, apatite layer was formed on nanostructured forsterite foam, which proved the good bioactivity of the prepared foam. It was concluded that two step sintering can prepare highly porous foams with appropriate compressive strength for tissue engineering applications.

Quasi-ballistic Electronic Thermal Conduction in Metal Inverse Opals.

Porous metals are used in interfacial transport applications that leverage the combination of electrical and/or thermal conductivity and the large available surface area. As nanomaterials push toward smaller pore sizes to increase the total surface area and reduce diffusion length scales, electron conduction within the metal scaffold becomes suppressed due to increased surface scattering. Here we observe the transition from diffusive to quasi-ballistic thermal conduction using metal inverse opals (IOs), which are metal films that contain a periodic arrangement of interconnected spherical pores. As the material dimensions are reduced from ∼230 nm to ∼23 nm, the thermal conductivity of copper IOs is reduced by more than 57% due to the increase in surface scattering. In contrast, nickel IOs exhibit diffusive-like conduction and have a constant thermal conductivity over this size regime. The quasi-ballistic nature of electron transport at these length scales is modeled considering the inverse opal geometry, surface scattering, and grain boundaries. Understanding the characteristics of electron conduction at the nanoscale is essential to minimizing the total resistance of porous metals for interfacial transport applications, such as the total electrical resistance of battery electrodes and the total thermal resistance of microscale heat exchangers.

A mechanical evaluation of micro-HA/CS composite scaffolds with interconnected spherical macropores.

BackgroundIn the process of bone defective reparation and engineered bone tissue construction, osteoblasts are adhered to the surface of the scaffold materials and impart the external mechanical load to the osteoblasts. So, the dynamic mechanical property of the scaffolds play an important role in the bone tissue repair and it is valuable to research. Material type and the architectural design of scaffolds are also important to facilitate cell and tissue growth. The aim of this study was to prepare a kind of material with good pore connectivity and analyze its dynamic mechanical property.MethodsFabrication and characterization of micro-hydroxyapatite(m-HA)/chitosan(CS) polymer composite scaffolds with well interconnected spherical pore architectures were reports. Micro-HA was prepared by being calcined and ball milled. Paraffin spheres in the range of 160–330 µm were fabricated with a dispersion method and used as the porogen in the fabrication of the scaffolds. Polymer scaffolds were fabricated by the technique of compression molding and particulate leaching method. The effects of the porogen content on the properties of the scaffolds were studied.ResultsWith the increase of porogen, the pore of the scaffolds increased and became interconnected. Cyclic loading of three scaffolds were tested with 10 % strain under four levels of loading frequency, 0.1, 0.5, 1 and 1.5 Hz. The porous composite scaffolds exhibited a viscosity-elastic behaviour with a maximum stress of 3–4 kPa. At each frequency, modulus value is decreased with the paraffin microspheres content, but there was no significance difference in the peak stress of the three samples. All the samples tested displayed clear hysteresis loops. There was no significance difference in the peak hysteresis of the three samples, and the hysteresis difference values between the sixth compression cycle and the initial cycle for three samples was similar, with no statistically significant differences.ConclusionsMicro-HA/CS composite scaffolds with interconnected spherical macropores were fabricated using pherical paraffin as porogen. The porous composite scaffolds exhibited a viscosity-elastic behaviour with good repeatability. It is benefit to study the influence of the mechanical load on the cell of the scaffold.

Fabrication and characterization of hydroxyapatite-coated forsterite scaffold for tissue regeneration applications

In this study, a novel hydroxyapatite (HA)-coated forsterite scaffold with a desired porous structure, high mechanical properties and good bioactivity was successfully fabricated via gel-casting and sol–gel in low pressure methods. X-ray diffraction, scanning electron microscopy, transmission electron microscopy and X-ray map techniques were utilized in order to evaluate the phase composition, dimension, morphology, interconnectivity of the pores and state of the coating on the porosities of the synthesized scaffold. The porosity and compressive strength of the scaffolds were measured and the bioactivity was investigated by soaking the scaffolds in simulated body fluid (SBF). The results show that the prepared scaffolds had highly interconnected spherical pores with size in the range of 65–245 μm. Additionally, compressive strength and elastic modulus were 7.5 ± 0.2 and 291 ± 10 MPa, respectively. The crystallite size of the scaffolds was less than 60 nm. True (total) and apparent (interconnected) porosity of the scaffolds were in the range of 75–80 and 65–70%, respectively. In vitro tests in the SBF also confirmed good bioactivity of the prepared scaffolds. While bone-like apatite formation started from the first day of soaking and apatite covered the entire surface and inner wall of the scaffolds pores at long immersion time. Conclusion suggested that HA coating on forsterite scaffolds could significantly improve the mechanical properties and bioactivity, which might be promising for tissue engineering applications.

Porous Sulfur/Polypyrrole/Multiwalled Carbon Nanotube Ternary Composite Cathode for Lithium/Sulfur Batteries

Introduction Lithium batteries have the highest energy density among the commercialized secondary batteries and they are leading the path for energy storage and sources for portable applications, including electric vehicle transportation. Commercial lithium batteries are based on oxide cathodes such as LiCoO2, LiFePO4 and LiMn2O4, which can deliver only up to 200 mAh g-1 of capacity, limiting their use for energy demanding applications. The elemental sulfur could be a best choice for the cathode due its theoretical capacity of 1672 mAh g-1, which is one of the highest among all known cathode materials. Combined with its abundant availability, this makes sulfur a most promising cathode for lithium batteries. However, this cathode material suffers from its low conductivity and capacity fading due to the dissolution of electrochemical reaction products [1, 2]. In this work, we report on the preparation of a novel hierarchical porous sulfur/polypyrrole/multiwalled carbon nanotube composite (S/PPy/MWNT), and on its physical and electrochemical properties as a cathode for lithium secondary batteries. Experimental The S/PPy/MWNT composite preparation is schematically presented in Fig.1. The porous S/PPy/MWNT composite was synthesized via in situpolymerization of pyrrole monomer with nano-sulfur and MWNT aqueous suspension followed by a low temperature heat-treatment. The S/PPy/MWNT composite was characterized using chemical analysis, XRD, SEM and HRTEM. The composite cathode electrode was prepared by mixing S/PPy/MWNT composite with conductive carbon and PVdF binder and coating this mixture on Al foil. The electrochemical properties of the composite cathode were investigated in a lithium half cell (coin-type CR2032) by cyclic voltammetry (CV) and galvanostatic cycling. Results and Discussion Figure 2 a present that SEM result, which reveal that a porous structure with interconnected spherical pores has been formed. While the pore sizes are about 500-1000 nm in diameter, the holes with the diameters of about 20-30 nm connect them with each other in the sample structure. This S/PPy/MWNT composite with hierarchical nano/microstructures can utilize the advantages of both nanometer-sized building blocks and micro- or submicrometer-sized assemblies. While the former could provide negligible lithium ion diffusion time and distances, and possibly a new Li storage mechanism for the favorable kinetics and high capacities, the latter could be beneficial to afford good stability of the electrode materials, which are important for enhancing the cycle performance of the electrodes. The elemental analysis (mapping) of the S/PPy/MWNT composite carried out by EDS is shown in Fig. 2 (b and c), demonstrating the existence and homogeneous distribution of sulfur and MWNT in the composite. Further development of this research will be presented at the Meeting.

Porous hydroxyapatite bioceramics in bone tissue engineering: current uses and perspectives

The goals of bone tissue engineering are to apply biomaterial scaffolds with adhered cells, such as osteoblasts, bone marrow stromal stem cells, or chondrocytes, to repair, regenerate, and restore the functions of damaged bone tissue or to replace those tissues with porous engineered biomaterials. Over recent decades, a diverse class of biomaterials has been applied in bone tissue engineering field. Porous hydroxyapatite bioceramic is currently receiving significant attention as a bone tissue engineering substitute because of its biological characteristics, including biocompatibility, bioactivity, osteoconduction, and vasculogenesis. This biomaterial has a three-dimensional structure with interconnected spherical pores of uniform size, which encourages bone ingrowth and achieves good integration of the material and the host bone over time. However, the compressive strength and elastic modulus of porous hydroxyapatite scaffolds generally weaken as the porosity increases, in both in vitro and in vivo testing. Zirconia can be used to toughen hydroxyapatite materials for bone repair and replacement because of its unique biomechanical properties, including compressive strength and fracture toughness. Additionally, a zirconia chitosan hybrid containing bone morphogenetic protein-2 and mesenchymal stem cells derived from induced pluripotent stem cells has been used as a coating material adhered to surface of scaffolds to promote bone regeneration and repair. Here, we provide a succinct review of zirconia toughened hydroxyapatite biomaterial scaffolds that incorporate bone morphogenetic protein-2 and mesenchymal stem cells for bone tissue engineering and describe the biomaterials that are currently being investigated based on the recent literature and our own data.

Random stacking template of polymer spheres and water soluble particles to fabricate porous hydroxyapatite with interconnected pores

Particle stacking simulation is applied in the fabrication of porous hydroxyapatite (HA) ceramics to predict the relationship between the template preparation process and the porosity of porous ceramics. The stacking of multi-diameter spherical particles, such as polymer spheres and NaCl particles, in three-dimensional space is simulated by using continuous generation method. The porosity of porous HA is predicted by calculating the stacking density of large spheres (the ratio of large sphere volume and container volume). The model of three-dimensional random stacking spheres is implemented by using the C++ program. Porous HA ceramics with interconnected spherical pores were fabricated by slipcasting which the use of a polymer template. Templates were produced by randomly stacking polymer spheres and NaCl particles. The arithmetic average error between the porosity of porous HA ceramics and the stacking density of polymer spheres (large spheres) is 3.52%. Simulation results obtained by using the proposed method are consistent with the experimental results.

Effect of solids concentration on pore structure of ZnO-foams prepared by particle-stabilized foaming route

An initially hydrophilic zinc oxide (ZnO) surface with a contact angle (θ) of ~32° has been changed to hydrophobic (θ~90°) through preferential adsorption of anionic sodium dodecul sulfate molecules on the particle surface by electrostatic interactions. Macroporous ZnO foams are prepared by anchoring the hydrophobic ZnO nanoparticles at the air/water interface to stabilize the air-in-water bubbles produced by mechanical frothing, followed then by sintering at elevated temperatures. Solids concentration (ϕ) of the ZnO suspensions is found critically important to pore structure of the sintered ZnO foams; in which, a broad pore-size distribution (~20–160μm) results and the pore volume decreases pronouncedly from 2.41mLg−1 to 0.85mLg−1 when ϕ was increased from 3vol% to 6vol%. The pore-volume difference stems primarily from the degree of coverage of the nanoparticles on the bubble surface. This is particularly pronounced for the suspension with ϕ of 3vol%; to which, interconnected spherical pores with a highly porous wall structure are formed because of the insufficient coverage. The process is indeed facile and is readily applicable to “one-pot” preparation of composite foams, such as ZnO foams decorated with discrete distribution of silver particles.