Controlled low-strength material (CLSM) is slurry made by mixing sand, cement, ash, and water. It is primarily used as a replacement for soil and structural fillings. This paper presents the findings of a preliminary investigation carried out on the performance of industrial waste incineration bottom ash as CLSM. CLSM mixes were designed using industrial waste incineration bottom ash, and cement. Tests for density, setting time, bleed, and compressive strength on cubes under various curing conditions, corrosivity, and leaching of heavy metals and salts were carried out on the CLSM mixtures, and the results discussed. Compressive strength for the designed CLSM mixtures ranged from 0.1 to 1.7 MPa. It is shown that the variations in curing conditions have less influence on the compressive strength of CLSM at high values of water to cement ratio (w/c), but low values of w/c influences the strength of CLSM. The CLSM produced does not exhibit corrosive characters as evidenced by pH. Leaching of heavy metals and salts is higher in bleed than in leachate collected from hardened CLSM. Cement reduces the leaching of Boron in bleed. It is concluded that there is good potential for the use of industrial waste incineration bottom ash in CLSM.
Fly ash samples from a mixed hazardous waste (MHW) incinerator were subjected to solidification and stabilization (S/S) studies using ordinary Portland cement (OPC) as the binder. Additives (i.e., activated carbon and rice husk) were also homogenized with the binder and waste to determine the effectiveness of the immobilization of heavy metals. The toxicity characteristics leaching procedure (TCLP), Japanese Leaching Test (JLT-13) and the American Nuclear Test 16.1 (modified) ANS 16.1 were used to gauge the leaching of heavy metals from the solidified matrixes. Compressibility strength of the solidified matrixes was also tested using the American Standard Testing Material (ASTM) test procedure for the compressive strength of hydraulic cement mortars.
Ageing is associated with geometrical changes in muscle fascicles that may lead to deteriorations in physical functions. The purpose of this study was to study the effects of ageing on fibre orientation and strength of the lumbar extensor muscles.
The paper discusses the influence of sintering temperature on the microstructure and strength of hydroxyapatite ceramics prepared using the extrusion process. The average pore diameters observed were in the range of approximately 150mm to 300mm whereas the compaction strength was found to be around 120-160 MPa.
This study aimed to investigate the structural, physical and mechanical behavior of composites and functionally graded materials (FGMs) made of stainless steel (SS-316L)/hydroxyapatite (HA) and SS-316L/calcium silicate (CS) employing powder metallurgical solid state sintering. The structural analysis using X-ray diffraction showed that the sintering at high temperature led to the reaction between compounds of the SS-316L and HA, while SS-316L and CS remained intact during the sintering process in composites of SS-316L/CS. A dimensional expansion was found in the composites made of 40 and 50 wt% HA. The minimum shrinkage was emerged in 50 wt% CS composite, while the maximum shrinkage was revealed in samples with pure SS-316L, HA and CS. Compressive mechanical properties of SS-316L/HA decreased sharply with increasing of HA content up to 20 wt% and gradually with CS content up to 50 wt% for SS-316L/CS composites. The mechanical properties of the FGM of SS-316L/HA dropped with increase in temperature, while it was improved for the FGM of SS-316L/CS with temperature enhancement. It has been found that the FGMs emerged a better compressive mechanical properties compared to both the composite systems. Therefore, the SS-316L/CS composites and their FGMs have superior compressive mechanical properties to the SS-316L/HA composites and their FGMs and also the newly developed FGMs of SS-316L/CS with improved mechanical and enhanced gradation in physical and structural properties can potentially be utilized in the components with load-bearing application.
Hydroxyapatite (HAp) is an attractive bioceramics due to its similar composition to bone mineral and its ability to promote bone-implant interaction. However, its low strength has limited its application as load bearing implants. This paper presented a work focusing on the improvement of HAp mechanical property by synthesizing iron (Fe)-reinforced bovine HAp nanocomposite powders via mechanosynthesis method. The synthesis process was performed using high energy milling at varied milling time (3, 6, 9, and 12h). The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), and scanning electron microscopy (SEM). Its mechanical properties were investigated by micro-Vicker's hardness and compression tests. Results showed that milling time directly influenced the characteristics of the nanocomposite powders. Amorphous BHAp was formed after 9 and 12h milling in the presence of HPO4(2-) ions. Continuous milling has improved the crystallinity of Fe without changing the HAp lattice structure. The nanocomposite powders were found in spherical shape, agglomerated and dense after longer milling time. The hardness and Young's modulus of the nanocomposites were also increased at 69% and 66%, respectively, as the milling time was prolonged from 3 to 12h. Therefore, the improvement of the mechanical properties of nanocomposite was attributed to high Fe crystallinity and homogenous, dense structure produced by mechanosynthesis.
There are a number of drawbacks to incorporating large concentrations of barium sulfate (BaSO4) as the radiopacifier in PMMA-based bone cements for percutaneous vertebroplasty. These include adverse effects on injectability, viscosity profile, setting time, mechanical properties of the cement and bone resorption. We have synthesized a novel cement that is designed to address some of these drawbacks. Its powder includes PMMA microspheres in which gold particles are embedded and its monomer is the same as that used in commercial cements for vertebroplasty. In comparison to one such commercial cement brand, VertaPlex™, the new cement has longer doughing time, longer injection time, higher compressive strength, higher compressive modulus, and is superior in terms of cytotoxicity. For augmentation of fractured fresh-frozen cadaveric vertebral bodies (T6-L5) using simulated vertebroplasty, results for compressive strength and compressive stiffness of the construct and the percentage of the volume of the vertebral body filled by the cement were comparable for the two cements although the radiopacity of the new cement was significantly lower than that for VertaPlex™. The present results indicate that the new cement warrants further study.
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.
The current study is proposing a design envelope for porous Ti-6Al-4V alloy femoral stems to survive under fatigue loads. Numerical computational analysis of these stems with a body-centered-cube (BCC) structure is conducted in ABAQUS. Femoral stems without shell and with various outer dense shell thicknesses (0.5, 1.0, 1.5, and 2 mm) and inner cores (porosities of 90, 77, 63, 47, 30, and 18%) are analyzed. A design space (envelope) is derived by using stem stiffnesses close to that of the femur bone, maximum fatigue stresses of 0.3σys in the porous part, and endurance limits of the dense part of the stems. The Soderberg approach is successfully employed to compute the factor of safety Nf > 1.1. Fully porous stems without dense shells are concluded to fail under fatigue load. It is thus safe to use the porous stems with a shell thickness of 1.5 and 2 mm for all porosities (18-90%), 1 mm shell with 18 and 30% porosities, and 0.5 mm shell with 18% porosity. The reduction in stress shielding was achieved by 28%. Porous stems incorporated BCC structures with dense shells and beads were successfully printed.
Recently, a modified form of a three-dimension (3D) porous poly(caprolactone-trifumarate) (PCLTF) scaffold has been produced using a fabrication technique that involves gelatin microparticles porogen leaching. This poly(caprolactone trifumarate-gelatin microparticles) (PCLTF-GMPs) scaffold has been shown to be biocompatible, more flowable clinically, and has a shorter degradation time as compared to its existing predecessors. In this report, a detailed characterization of this new scaffold was performed by testing its cytocompatibility, analyzing the surface topography, and understanding its thermal, physical and mechanical properties. The result showed that the PCLTF-GMPs has no critical cytotoxic effect. To confirm improvement, the surface properties were compared against the older version of PCLTF fabricated using salt porogen leaching. This PCLTF-GMPs scaffold showed no significant difference (unpaired t-test; p>0.05) in mechanical properties before and after gelatin leaching. However, it is mechanically weaker when compared to its predecessors. It has a high biodegradability rate of 16weeks. The pore size produced ranges from 40 to 300μm, and the RMS roughness is 613.7±236.9nm. These characteristics are condusive for osteoblast in-growth, as observed by the extension of filopodia across the macropores. Overall, this newly produced material has good thermal, physical and mechanical properties that complements its biocompatibility and ease of use.
This study describes the synthesis of Al(2)O(3)/SiC/ZrO(2) functionally graded material (FGM) in bio-implants (artificial joints) by electrophoretic deposition (EPD). A suitable suspension that was based on 2-butanone was applied for the EPD of Al(2)O(3)/SiC/ZrO(2), and a pressureless sintering process was applied as a presintering. Hot isostatic pressing (HIP) was used to densify the deposit, with beneficial mechanical properties after 2 h at 1800 °C in Ar atmosphere. The maximum hardness in the outer layer (90 vol.% Al(2)O(3)+10 vol.% SiC) and maximum fracture toughness in the core layer (75 vol.% Al(2)O(3)+10 vol.% SiC + 15 vol.% ZrO(2)) composite were 20.8±0.3 GPa and 8±0.1 MPa m(1/2), respectively. The results, when compared with results from Al(2)O(3)/ZrO(2) FGM, showed that SiC increased the compressive stresses in the outer layers, while the inner layers were under a residual tensile stress.
A novel porous three-dimensional bone scaffold was developed using a natural polymer (alginate/Alg) in combination with a naturally obtained biomineral (nano cockle shell powder/nCP) through lyophilization techniques. The scaffold was developed in varying composition mixture of Alg-nCP and characterized using various evaluation techniques as well as preliminary in vitro studies on MG63 human osteoblast cells. Morphological observations using SEM revealed variations in structures with the use of different Alg-nCP composition ratios. All the developed scaffolds showed a porous structure with pore sizes ideal for facilitating new bone growth; however, not all combination mixtures showed subsequent favorable characteristics to be used for biological applications. Scaffolds produced using the combination mixture of 40% Alg and 60% nCP produced significantly promising results in terms of mechanical strength, degradation rate, and increased cell proliferation rates making it potentially the optimum composition mixture of Alg-nCP with future application prospects.
A mechanical-conditioning bioreactor has been developed to provide bi-axial loading to three-dimensional (3D) tissue constructs within a highly controlled environment. The computer-controlled bioreactor is capable of applying axial compressive and shear deformations, individually or simultaneously at various regimes of strain and frequency. The reliability and reproducibility of the system were verified through validation of the spatial and temporal accuracy of platen movement, which was maintained over the operating length of the system. In the presence of actual specimens, the system was verified to be able to deliver precise bi-axial load to the specimens, in which the deformation of every specimen was observed to be relatively homogeneous. The primary use of the bioreactor is in the culture of chondrocytes seeded within an agarose hydrogel while subjected to physiological compressive and shear deformation. The system has been designed specifically to permit the repeatable quantification and characterisation of the biosynthetic activity of cells in response to a wide range of short and long term multi-dimensional loading regimes.
This paper presents the development of novel alternative injectable calcium phosphate cement (CPC) composites for orthopaedic applications. The new CPC composites comprise β-tri-calcium phosphate (β-TCP) and di-calcium phosphate anhydrous (DCPA) mixed with bovine serum albumin (BSA) and incorporated with multi-walled carbon nanotubes (MWCNTs) or functionalized MWCNTs (MWCNTs-OH and MWCNTs-COOH). Scanning electron microscopy (SEM), compressive strength tests, injectability tests, Fourier transform infrared spectroscopy and X-ray diffraction were used to evaluate the properties of the final products. Compressive strength tests and SEM observations demonstrated particularly that the concomitant admixture of BSA and MWCNT improved the mechanical properties, resulting in stronger CPC composites. The presence of MWCNTs and BSA influenced the morphology of the hydroxyapatite (HA) crystals in the CPC matrix. BSA was found to act as a promoter of HA growth when bounded to the surface of CPC grains. MWCNT-OH-containing composites exhibited the highest compressive strengths (16.3 MPa), being in the range of values for trabecular bone (2-12 MPa).
An injectable poly(DL-lactic-co-glycolic acid) (PLGA) system comprising both porous and protein-loaded microspheres capable of forming porous scaffolds at body temperature was developed for tissue regeneration purposes. Porous and non-porous (lysozyme loaded) PLGA microspheres were formulated to represent 'low molecular weight' 22-34 kDa, 'intermediate molecular weight' (IMW) 53 kDa and 'high molecular weight' 84-109 kDa PLGA microspheres. The respective average size of the microspheres was directly related to the polymer molecular weight. An initial burst release of lysozyme was observed from both microspheres and scaffolds on day 1. In the case of the lysozyme-loaded microspheres, this burst release was inversely related to the polymer molecular weight. Similarly, scaffolds loaded with 1 mg lysozyme/g of scaffold exhibited an inverse release relationship with polymer molecular weight. The burst release was highest amongst IMW scaffolds loaded with 2 and 3 mg/g. Sustained lysozyme release was observed after day 1 over 50 days (microspheres) and 30 days (scaffolds). The compressive strengths of the scaffolds were found to be inversely proportional to PLGA molecular weight at each lysozyme loading. Surface analysis indicated that some of the loaded lysozyme was distributed on the surfaces of the microspheres and thus responsible for the burst release observed. Overall the data demonstrates the potential of the scaffolds for use in tissue regeneration.
The ability of inkjet-based 3D printing (3DP) to fabricate biocompatible ceramics has made it one of the most favorable techniques to generate bone tissue engineering (BTE) scaffolds. Calcium sulfates exhibit various beneficial characteristics, and they can be used as a promising biomaterial in BTE. However, low mechanical performance caused by the brittle character of ceramic materials is the main weakness of 3DP calcium sulfate scaffolds. Moreover, the presence of certain organic matters in the starting powder and binder solution causes products to have high toxicity levels. A post-processing treatment is usually employed to improve the physical, chemical, and biological behaviors of the printed scaffolds. In this study, the effects of heat treatment on the structural, mechanical, and physical characteristics of 3DP calcium sulfate prototypes were investigated. Different microscopy and spectroscopy methods were employed to characterize the printed prototypes. The in vitro cytotoxicity of the specimens was also evaluated before and after heat treatment. Results showed that the as-printed scaffolds and specimens heat treated at 300°C exhibited severe toxicity in vitro but had almost adequate strength. By contrast, the specimens heat treated in the 500°C-1000°C temperature range, although non-toxic, had insufficient mechanical strength, which was mainly attributed to the exit of the organic binder before 500°C and the absence of sufficient densification below 1000°C. The sintering process was accelerated at temperatures higher than 1000°C, resulting in higher compressive strength and less cytotoxicity. An anhydrous form of calcium sulfate was the only crystalline phase existing in the samples heated at 500°C-1150°C. The formation of calcium oxide caused by partial decomposition of calcium sulfate was observed in the specimens heat treated at temperatures higher than 1200°C. Although considerable improvements in cell viability of heat-treated scaffolds were observed in this study, the mechanical properties were not significantly improved, requiring further investigations. However, the findings of this study give a better insight into the complex nature of the problem in the fabrication of synthetic bone grafts and scaffolds via post-fabrication treatment of 3DP calcium sulfate prototypes.
This study was aimed to improve of the corrosion resistance and mechanical properties of Mg/15TiO2/5HA nanocomposite by silicon and magnesium oxide coatings prepared using a powder metallurgy method. The phase evolution, chemical composition, microstructure and mechanical properties of uncoated and coated samples were characterized. Electrochemical and immersion tests used to investigate the in vitro corrosion behavior of the fabricated samples. The adhesion strength of ~36MPa for MgO and ~32MPa for Si/MgO coatings to substrate was measured by adhesion test. Fabrication a homogenous double layer coating with uniform thicknesses consisting micro-sized particles of Si as outer layer and flake-like particles of MgO as the inner layer on the surface of Mg/15TiO2/5HA nanocomposite caused the corrosion resistance and ductility increased whereas the ultimate compressive stress decreased. However, after immersion in SBF solution, Si/MgO-coated sample indicates the best mechanical properties compared to those of the uncoated and MgO-coated samples. The increase of cell viability percentage of the normal human osteoblast (NHOst) cells indicates the improvement in biocompatibility of Mg/15TiO2/5HA nanocomposite by Si/MgO coating.
Magnesium (Mg) alloys present great potential for the development of orthopedic implants, whereas, their high degradation rate and poor antibacterial performance have restricted orthopedic applications. In this work, PLLA/GO-AgNP (poly-L-lactic acid/graphene oxide- silver nanoparticle) with different concentration of GO-AgNPs were deposited on Mg alloy via electrospinning method for enhancement of corrosion resistance and antibacterial performance. The result revealed that incorporation of GO into PLLA fibrous considerably slowed down the degradation rate of Mg alloy substrate and reduced the H2 release rate from the substrate. Also, co-incorporation of GO and AgNPs into PLLA fibrous resulted in substantial escalate in compressive strength after immersion in simulated body fluid (SBF). Antibacterial activity test exhibited that Mg alloy and neat PLLA fibrous presented minimal inhibition area toward Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). In contrast, using PLLA/GO-AgNPs fibrous improved antibacterial performance against both bacteria. Cytocompatibility results indicated that PLLA/GO-AgNPs fibrous with a low amount of GO-AgNPs enhanced cell proliferation and growth while high co-incorporation of GO-AgNPs showed a negative effect on cell proliferation. Taken together, PLLA/1GO-AgNPs fibrous coating shows suitable corrosion resistance, cytocompatibility, and antibacterial function for use in orthopedic applications.
Cross-linked soy protein isolate (SPI) gels were produced via single-treatment of SPI with microbial transglutaminase (MTG) for 5 h or 24 h, or with ribose for 2 h, or via combined-treatments of SPI with MTG followed by heating with ribose. Assessment of gel strength and solubility concluded that measures which increased protein cross-links resulted in improved gel strength; however, in most cases the digestibility and amino acid content of the gels were reduced. The combined treated gel of SPI/MTG for 24 h/ribose was more easily digested by digestive enzymes and retained higher amounts of amino acids compared with the control Maillard gels of SPI with ribose. MTG consumed lysine and glutamine and reduced the availability of amino acids for the Maillard reaction with ribose. MTG was able to preserve the nutritional value of SPI against the destructive effect of the Maillard reaction and cross-links.