Polymeric Sponge Method Research Articles

Magnesium-enhanced porous hydroxyapatite ceramics: Morphometric parameters, physical properties and bioactivity

The application of porous bioactive ceramics as bone substitutes requires their effective osseointegration, which relies on specific physical and biological properties. In this study, we developed porous magnesium-doped hydroxyapatite (MgHA) ceramics with four different magnesium concentrations (0.25, 2, 5 and 10 mol%). The ceramics were prepared through the polymeric replication sponge method and subjected to physical and biological characterizations. Upon sintering, the porous 10 mol% MgHA ceramics exhibited increased densification, which resulted in the highest compressive strength of 2.17 MPa at the lowest porosity of 31 %.The porous samples were analysed via microcomputed tomography. The scaffolds with 0.25 and 10 mol% Mg doping concentrations were selected to elucidate the influence of Mg on morphometric parameters and biological properties at two distinct levels. The high level of Mg doping led to considerable improvements in relative bone volume, connectivity density, trabecular number and trabecular thickness. Cell attachment and proliferation tests using Vero cell lines were conducted on both samples to investigate the correlations between their morphometric parameters and bioactivities. Substantially more cells attached to and proliferated on the surface of the 10 mol% MgHA ceramics compared with those on the ceramics containing 0.25 mol% MgHA. In summary, our study underscores the effectiveness of Mg incorporation in improving the physical and biological properties of porous HA ceramics, which makes them promising candidates for bone substitute applications.

Effect of Adding Titania and Alumina on the Bioactivity Properties of Porous Hydroxyapatite via Replication Method for Bone Reconstruction

In this investigation, Hydroxyapatite/Titania and hydroxyapatite/Alumina porous composites at five various proportions were manufactured by replication method A.K.A the polymeric sponge method. HAp powder was fabricated by a “solid-state reaction” in molar proportion between (TCP)Tri calcium phosphate and Ca(OH)2 Calcium hydroxide. The microstructures were examined by utilizing (XRD), (SEM) and EDX”. Incubated for thirty days in SBF (Simulation Body Fluid),a thin layer like apatite formed completely on a bone specially on the surface of the samples was.. There’s a very low degeneracy degree when amount of the reinforcements materials increased..

A novel modification for polymer sponge method to fabricate the highly porous composite bone scaffolds with large aspect ratio suitable for repairing critical-sized bone defects

In this paper, a modified version of the polymer sponge method is proposed to fabricate some porous composite bone scaffolds consisting of hydroxyapatite (HA) and alumina. Findings of the current paper show that the modified polymer sponge scheme presented in this study results in the scaffolds with superior physical and mechanical properties in comparison with the classical foam replica technique which is commonly used in the literature. Scaffolds with the total and open porosity of 75.22 ± 2.97% and 68.19 ± 1.61%, respectively, were achieved by the proposed method. Furthermore, the value of the compressive strength of the fabricated scaffolds was 4.25 ± 0.73 MPa which is good for bone tissue engineering applications. The innovative scheme presented in this paper makes it possible to produce the samples with the large aspect ratio which are suitable for repairing critical-sized bone defects.

Preparation of Hydroxyapatite/Zirconia Porous Composites via Polymeric Sponge Method and Study the Physical and Bioactivity Properties

In this study, Hydroxyapatite/Zirconia porous composites at different ratio were fabricated by polymeric sponge method. HAp were produced via solid state reaction in molar ratio (3:2) between TCP and Ca(OH)2. The crystal structure of the samples were characterized using X-ray diffractometer (XRD), scanning electron microscopy (SEM). Furthermore, the porosity and rheological properties of the samples were also tested. It’s found that the compression strength with the highest value (13.2 MPa) obtained when the composition ratio is (30:70 wt %) and porosity (65.7%). Incubated for 30 days in Simulation Body Fluid, a bone like apatite layer was completely formed on the surface of the porous composite.

Preparation and Characterization of Akermanite/Merwinite Scaffolds for Bone Tissue Repair

The ceramics in the system CaO–MgO–SiO2 has recently attracted a great deal of attention because they display a good in vitro bioactivity and have potential use as bone implants. Biphasic calcium-magnesium-silicate ceramics were prepared by a sol-gel method. The dried gel with chemical composition 3CaO.MgO.2SiO2 was thermally treated at 1200 °C for 2 hrs. The structural behavior of the synthesized ceramics was examined by means of X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). Merwinite crystalline phase and akermanite phase were recognized. Then, porous akermanite/merwinite scaffolds were prepared to utilize polymer sponge method and evaluated by employing SEM. Furthermore, bone marrow stromal cells (BMSC) adhesion and proliferation on the scaffolds were evaluated by MTT assay test. Differentiation of the cells was assessed by measuring alkaline phosphatase (ALP) activity. The results demonstrated that BMSC adhered and spread well on akermanite scaffolds and proliferated with the increase in the culture time, and the differentiation rate of osteoblasts on scaffolds was comparable to that on blank culture plate control. Thus, the obtained results presented that the akermanite/merwinite scaffolds deserve attention for bone tissue engineering applications.

Three-Dimensional Garnet Framework-Reinforced Solid Composite Electrolytes with High Lithium-Ion Conductivity and Excellent Stability.

We report a three-dimensional (3D) garnet framework-reinforced solid composite electrolyte with enhanced Li-ion conductivity and excellent thermal, mechanical, and electrochemical stabilities. The 3D garnet framework is fabricated via the polymeric sponge method, using low-cost polyurethane foam as the template. The interconnected 3D garnet framework not only reinforces the composite electrolyte but also forms continuous Li-ion transport pathways, thereby increasing the ionic conductivity. The 3D garnet composite electrolyte shows an ionic conductivity of 1.2 × 10-4 S cm-1 at 30 °C, about two times as high as that of the garnet particle-reinforced composite electrolyte. The Li-Li symmetric cell based on the 3D garnet composite electrolyte can be cycled more than 360 h without short circuit, suggesting an improved ability to suppress Li-dendrites. The Li/3D garnet composite electrolyte/LiFePO4 battery demonstrates stable cycling performance at 0.5 C. Owing to the cost-saving characteristics, the 3D garnet-reinforced solid composite electrolyte is promising for mass production.

The physicochemical and biomechanical profile of forsterite and its osteogenic potential of mesenchymal stromal cells.

It has been demonstrated that nanocrystalline forsterite powder synthesised using urea as a fuel in sol-gel combustion method had produced a pure forsterite (FU) and possessed superior bioactive characteristics such as bone apatite formation and antibacterial properties. In the present study, 3D-scaffold was fabricated using nanocrystalline forsterite powder in polymer sponge method. The FU scaffold was used in investigating the physicochemical, biomechanics, cell attachment, in vitro biocompatibility and osteogenic differentiation properties. For physicochemical characterisation, Fourier-transform infrared spectroscopy (FTIR), Energy dispersive X-ray (EDX), X-ray diffraction (XRD), Raman spectroscopy, X-ray photoemission spectrometer (XPS) and Brunauer-Emmett-Teller (BET) were used. FTIR, EDX, XRD peaks and Raman spectroscopy demonstrated correlating to FU. The XPS confirmed the surface chemistry associating to FU. The BET revealed FU scaffold surface area of 12.67 m2/g and total pore size of 0.03 cm3/g. Compressive strength of the FU scaffold was found to be 27.18 ± 13.4 MPa. The human bone marrow derived mesenchymal stromal cells (hBMSCs) characterisation prior to perform seeding on FU scaffold verified the stromal cell phenotypic and lineage commitments. SEM, confocal images and presto blue viability assay suggested good cell attachment and proliferation of hBMSCs on FU scaffold and comparable to a commercial bone substitutes (cBS). Osteogenic proteins and gene expression from day 7 onward indicated FU scaffold had a significant osteogenic potential (p<0.05), when compared with day 1 as well as between FU and cBS. These findings suggest that FU scaffold has a greater potential for use in orthopaedic and/or orthodontic applications.

Effect of SiO&lt;sub&gt;2&lt;/sub&gt; Solid Loading and Sintering Temperatures on the Physical Properties of SiO&lt;sub&gt;2&lt;/sub&gt;-NiO Foam

Porous ceramic is a type of material that has highly open and partially interconnected pores. It has a wide range of applications which include catalyst support, electrical conductivity, refractory insulation of furnaces, filtration, adsorption, and separation. There are many conventional methods for producing silica foam including direct forming, steam heating, freeze casting and the polymeric sponge method which is also known as the replication method. In this study, SiO2-NiO foam was fabricated using 25wt. %, 30wt % and 35wt.% of SiO2 and 5wt.% of NiO under different sintering temperatures (850 °C and 1050 °C) via replication method. The morphologies of SiO2-NiO foams were observed using Scanning Electron Microscopy (SEM) while the identification of the different phases of foam was analysed using X-Ray Diffraction (XRD). The XRD analysis indicated that there were only SiO2 and NiO present and no additional phases were detected after sintering. The effects of sintering temperature (850 °C, 1050 °C) and SiO2 solid loading on properties such as apparent porosity, bulk density and shrinkage were investigated. It was found that when the solid loading of SiO2 and sintering temperature increased, the density of SiO2-NiO foams increased in the range of 0.6373 g/cm3 to 0.8165 g/cm3. On the other hand, the porosity percentage obtained increased from 78.51 % to 81.63 %. The density and porosity analyses showed that the density of foam increases when the porosity of SiO2-NiO foam decreases. However, the shrinkage after sintering ranged between 3.5081cm to 6.9975 cm at 850C ̊ and 7.3618 cm to 8.3704 cm at 1050 °C respectively. Thus, this proves that SiO2-NiO foam can be successfully fabricated through the replication method.

Investigation Effect of Different Feldspar Ratio on the Mechanical Properties of Porcelain Ceramic Foam Prepared by Polymeric Sponge Method

Investigation Effect of Different Feldspar Ratio on the Mechanical Properties of Porcelain Ceramic Foam Prepared by Polymeric Sponge Method

Processing of layered porous mullite ceramics

In the current study, layered porous mullite ceramics with different pore sizes were produced via polymeric sponge method by using CC31 commercial-grade kaolin as starting raw material. Polyurethane sponges with three different pore sizes (10, 20, and 30 ppi) changing from coarse to fine pores were physically assembled and then prepared ceramic slurry was impregnated into this structure to achieve the designed layered porous structure. After drying the polymeric sponges impregnated with the slurry, binder burnout and sintering studies were carried out. Phase composition and microstructure evolution of the porous samples, sintered at 1300°-1600°C for 1 and 3 h dwell time at a 3°C/minute constant heating rate, were investigated. In situ mullite phase formation was achieved at all sintering conditions. It was determined that mullite grain morphology development strongly depends on the sintering temperature and time. Sintering at 1300 °C for 1 h resulted in the formation of equiaxed mullite grains. When the sintering temperature was increased to 1400 °C, first elongated fine mullite grains were achieved. Increasing dwell time at this temperature from 1 to 3 h resulted in more elongated mullite grain development. It was observed that aspect ratio of the mullite grains was significantly increased when the sintering temperature was increased to 1500 and 1600 °C. Scanning electron microscopy investigations demonstrated that the mullite needles do not reveal a significant preferred orientation and all porous mullite samples have uniform microstructure. It was determined that highly porous (60–70%) and light weight (0.7–1.1 g cm−3) layered mullite ceramics were fabricated.

Biphasic calcium phosphate scaffolds with controlled pore size distribution prepared by in-situ foaming

In this study, a reproducible method of fabricating hierarchically 3D porous scaffolds with high porosity and pore interconnectivity is reported. The method is based on in-situ foaming of a dispersion of diisocyanate, polyol, water and hydroxyapatite (HA) to form a hard foamed HA/polyurethane composite which after heat treatment provided a bi-phase calcium phosphate scaffold. This technique, combining the advantages of polymer sponge and direct foaming methods, provides a better control over the macrostructure of the scaffold. A modification of the multi-scaled porous macrostructure of scaffolds produced by changing the ratio of input reactants and by sintering temperature was studied. The pore morphology, size, and distribution were characterized using a scanning electron microscope and mercury porosimetry. The pores were open and interconnected with multi-scale (from several nanometres to millimetres) sizes convenient for using in tissue engineering applications. The bioactivity was confirmed by growing an apatite layer on the surfaces after immersion in simulated body fluid. The material was biocompatible, as shown by using normal human adipose tissue-derived stem cells (ASC). When seeded onto the scaffolds, the ASC adhered and remained healthy while maintaining their typical morphology.

PZT/PLZT - elastomer composites with improved piezoelectric voltage coefficient

Lead Zirconate Titanate (PZT) and Lanthanum-modified Lead Zirconate Titanate (PLZT) ceramic sensor materials are widely used because of their excellent piezoelectric coefficients. These materials are brittle, high density and have low achievable piezoelectric voltage coefficients. The density of the sintered ceramics shall be reduced by burnable polymeric sponge method. The achievable porosity level in this case is nearly 60 – 90%. However, the porous ceramic structure with 3-3 connectivity produced by this method is very fragile in nature. The strength of the porous structure is improved with Sylgard®-184 (silicone elastomer) by vacuum impregnation method maintaining the dynamic vacuum level in the range of -650 mm Hg. The elastomer Sylgard®-184 is having low density, low dielectric constant and high compliance (as a resultant stiffness of the composites is increased). To obtain a net dipole moment, the impregnated ceramic composites were subjected to poling treatment with varying conditions of D.C. field and temperature. The properties of the poled PZT/PLZT - elastomer composites were characterized with LCR meter for measuring the dielectric constant values (k), d33 meter used for measuring piezo-electric charge coefficient values (d33) and piezo-electric voltage coefficient (g33) values which were derived from d33 values. The voltage coefficient (g33) values of these composites are increased by 10 fold as compared to the conventional solid ceramics demonstrates that it is possible to fabricate a conformable detector.

Coagulated concentrated anatase slurry leads to improved strength of ceramic TiO2 bone scaffolds

Slurry behaviour has an important influence on the properties of ceramic scaffolds produced by the polymer sponge method. By adding chloride salts to the TiO2 slurry, the viscosity was increased depending on the chloride concentration at low pH and high particle concentration. Slurries with higher viscosity led to closed and dense scaffold struts combined with high porosity, resulting in a compressive strength over 1.6MPa. Furthermore, scaffold prepared with 0.1M CaCl2 and SrCl2 showed the formation of Ca- and Sr-rich phases at the grain boundaries. These ions were also shown to reduce the activation energy for grain growth in the TiO2 scaffold as indicated by the significantly larger grain size. Ca2+-doped scaffolds had the highest compressive strength, while the strength of Sr2+-doped scaffolds was reduced by the formation of a solid solution phase below the sintering temperature.

Obtainment of Porous Ceramic Structures: A Comparison among Different Compositions and Methods of Conformation

This paper presents comparative results concerning to the obtaining of porous ceramic structures obtained by pressing, slip casting and polymeric sponge method. Three compositions were prepared, using calcium carbonate as pore-generating agent and characterized by X-ray fluorescence, thermogravimetric analysis and determination of sintering behavior. Each formulation was wet mixed and dried. Then, each formulation was formed by each one of the investigated methods. The obtained samples were dried and heat treated with the appropriate heating rate for calcium carbonate degasification and sintered at 900, 1100 and 1180 °C. The sintered samples were characterized by determination of porosity, crystalline phases formed, compressive strength and permeability. Results showed that porosity and permeability depends strongly on the composition and used conformation method.

Effect of Pressure and Temperature in Solid State Sintering Approach Producing Porous Tricalcium Phosphate Bioceramics

Porous Tricalcium Phosphate (TCP) is recognized as a good biomaterial having excellent biocompatibility, biodegrability and bioresorbability. Some of the techniques to produce porous β-TCP, are replica technique (polymeric sponge method), sacrificial template method and direct forming method, however, these methods are complicated and can be costly. In this study, solid state sintering was adopted to form porous TCP as a new approach to overcome these problems. TCP bioceramic was prepared by mixing calcium hydrogen phosphate dihydrate and calcium carbonate. The powders were pressed into pellet form with four different pressures; 10, 20, 30 and 40 MPa. Then, the pellets were sintered at 1100°C to 1400°C and subsequently characterized by X-ray diffraction (XRD), density and porosity measurement, diametral tensile strength test (DTS) and scanning electron microscopy (SEM) evaluation. β-TCP phase was maintained at 1100°C and 1200°C whilst α-TCP phase had formed as second phase above 1300°C. The highest apparent porosity (60.93%) was obtained at 10 MPa and 1100°C sintering temperature, with the density of 1.12 g/cm3. The DTS values were in the range of 0.31 to 3.78 MPa in with lower DTS values were obtained at low compaction pressure and sintering temperature. Interconnected pores with high level porosity were observed at the fracture surfaces of the sintered pellets. Intraporosity was also observed. In conclusion, TCP bioceramics with interconnected pores were produced via solid state reaction; however, more work is required to improve the level of porosity.

Influence of sodium on the properties of sol-gel derived hydroxyapatite powder and porous scaffolds

Abstract This study investigates the properties of sol-gel derived sodium (Na)-doped hydroxyapatite (HA) powder. Different amounts of Na (1, 5, 10 and 15 mol%) were prepared and the sintered bodies were characterized to determine the current phases, microstructural evolution and mechanical properties. X-ray diffraction analysis reveals that a phase pure HA of crystallite sizes, which varied from 35 nm to 65 nm, was obtained in the synthesized powder after calcining from 500 °C to 1000 °C. Scanning electron microscopy examination shows evidence of larger particle sizes, particularly in samples that contain higher amounts of Na concentration. The resultant powders were subsequently used to prepare porous NA-doped HA bodies through a polymeric sponge method. The addition of 5% Na resulted in a porous body with 27% porosity and was beneficial in enhancing the compressive strength of HA 17-fold compared with undoped HA. The prepared scaffold also shows suitable pore interconnectivity with pore sizes that vary between 100 and 300 µm which is suitable for use as porous bone substitutes.

Caracterização microestrutural de compósitos de hidroxiapatita-alumina confeccionados pelo método da esponja polimérica

Resumo O aumento do número de cirurgias de substituição e reparação óssea propiciou o estudo e a disseminação do uso de biomateriais, devido à sua biocompatibilidade e custo inferior ao de outros materiais utilizados como implantes. A hidroxiapatita é um biomaterial eficaz para utilização em engenharia tecidual, por ela fazer parte da matriz óssea. Porém, sua baixa resistência mecânica torna necessária a adição de outros materiais objetivando aumentar tal propriedade. A alumina é um material bioinerte que tem sido bastante utilizado como reforço mecânico para a hidroxiapatita. Este trabalho buscou desenvolver, pelo método da esponja polimérica, arcabouços cerâmicos de hidroxiapatita-alumina nas proporções em massa 50%-50%, 60%-40% e 70%-30. Os corpos de prova foram calcinados a 550 °C e sinterizados a 1250, 1300 e 1350 °C para avaliar características microestruturais. Os resultados obtidos estão de acordo com a literatura, o que justifica a realização de ensaios de caracterização físico-mecânica.

The effect of macro/micro combination pore structure of biphasic calcium phosphate scaffold on bioactivity

Cellular responses such as adhesion, spreading, growth and proliferation can be altered by macro and micro pores as well as surface patterns on its surface. In this study, the scaffold was prepared with interconnected macro pores by the polymeric sponge method and with interconnected micro pores by BCP slurry coating with different particle sizes on sintered porous body and necking sintering process. Two particle sizes for micro pores, 200–400nm and 600–800nm, were coated on a pre-sintered porous body. A combined macro and micro pore structure of the BCP scaffold can improve osteoblast cellular activity. In vitro study of MG63 cells suggest that the modified scaffolds improved cell response such as cell spreading, proliferation and differentiation. The scaffold that has a uniform distribution of micro pores ranging 1~5µm in diameter on its surface yields the highest rate of cellular response.

Preparation and characterization of highly porous ceramic scaffolds based on thermally treated fish bone

The present study aims at the preparation of highly porous 3D scaffolds from the biological resource; fish bone skeletons. To the best of the authors׳ knowledge, few works were reported for preparation of highly porous scaffolds from biogenic hydroxyapatite. The preparation method includes two essential steps: the first is the extraction of pure hydroxyapatite powder having an average particle size of 50–80nm from fish bone skeletons. The second is the formation of highly porous hydroxyapatite scaffolds prepared from fish bone skeletons via polymeric sponge method. Such scaffolds are highly bioactive as they are able to attract calcium and phosphorous ions to the scaffold surface in a very short time; less than one hour. The produced hydroxyapatite powder was investigated using transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR), while the formed porous scaffolds were evaluated for their physical and chemical properties in addition to their pore size, microstructure and bioactivity.The results revealed that the porosity of the obtained 3D scaffolds is 85±0.4 and the median pore diameter ranging between about 1 and 3μm. The compressive and bending strengths of the scaffolds are 0.13±0.007MPa and 1.72±0.02MPa respectively, which is very near to the strength of trabecular bone.

Porous bodies of hydroxyapatite produced by a combination of the gel-casting and polymer sponge methods

A combination of gel-casting and polymeric foam infiltration methods is used in this study to prepare porous bodies of hydroxyapatite (HA), to provide a better control over the microstructures of samples. These scaffolds were prepared by impregnating a body of porous polyurethane foam with slurry containing HA powder, and using a percentage of solids between 40% and 50% w/v, and three different types of monomers to provide a better performance. X-Ray Diffraction (XRD), and Fourier Transformed Infrared (FTIR) and Scanning Electron Microscopy (SEM) were employed to evaluate both the powder hydroxyapatite and the scaffolds obtained. In addition, porosity and interconnectivity measurements were taken in accordance with the international norm. Bioactivity was checked using immersion tests in Simulated Body Fluids (SBF). After the sintering process of the porous bodies, the XRD results showed peaks characteristic of a pure and crystalline HA (JCPDS 9-432) as a single phase. SEM images indicate open and interconnected pores inside the material, with pore sizes between 50 and 600μm. Also, SEM images demonstrate the relatively good bioactivity of the HA scaffolds after immersion in SBF. All results for the porous HA bodies suggest that these materials have great potential for use in tissue engineering.