Novel β-TCP scaffold production using NaCl as a porogen for bone tissue applications

There are numerous methods for producing scaffolds to be applied in bone tissue engineering. However, the best method of scaffold production is essential to consider, with respect to their chemical composition and mechanical and structural properties, so that debris is not produced when the scaffolds are evaluated in vitro or in vivo.The primary aim of the present investigation was to produce six novel β-TCP scaffold compositions, using sodium chloride as a porogen, with two different particle sizes, measuring 1–2 mm and 750 mm-1mm, and at varied concentrations (30, 50, and 70 wt %). Physical, chemical, mechanical, and in vitro characterizations were then performed on each scaffold composition, using artificial saliva, for 7 and 14 days, with promising results. The XRD diffractograms showed the formation of two new crystalline phases (NaCaPO₄ and Ca₅[PO₄]₃Cl) in the scaffolds, after their production. In addition, scaffold porosity, Young's modulus, and the maximum resistance of compression values were in the trabecular bone range and the in vitro test, using artificial saliva, was favorable in relation to scaffold bioactivity.     

Ultra-thin carbon nanosheets coated with SnO2–NbC nanoparticles as high-performance anode materials for lithium-ion batteries

A SnO₂–NbC–C ternary composite was constructed using hydrothermal and ball milling methods. For this special design, the SnO₂–NbC nanoparticles were uniformly coated with ultra-thin carbon nanosheets. It should be noted that the NbC nanoparticles can accommodate the volume variation of SnO₂ particles and prevent Sn agglomeration, resulting in good electrical contact between particles and low charge transfer resistance. After 100 cycles of 0.2 Ag^-1, the SnO₂–NbC–C nanocomposite exhibited a high capacity of 956.0 mAhg^-1, and a rate capacity of 955.2 mAhg^-1, and after 500 cycles of 5.0 Ag^-1, it achieved a capacity of 704.1 mAhg^-1. In addition, the SnO₂–NbC–C composite remained stable after 200 and 700 cycles without agglomeration.     

Development and characterization of printable PLA/β-TCP bioactive composites for bone tissue applications

In this study, poly(lactic acid) (PLA) and PLA/β-tricalcium phosphate (TCP) biocomposites were developed by melt compounding using an internal melt mixer with three different TCP contents (5, 10, and 25 wt%). A comprehensive analysis of the thermal, rheological, and mechanical properties of these biocomposites was performed. TCP presented proper distribution in the PLA/TCP biocomposites: PLA5TCP and PLA10TCP exhibited rheological behavior similar to that of neat PLA. However, PLA25TCP presented significant agglomeration and reduction in thermal stability. Addition of TCP to the biocomposites enhanced their bioactivity and biocompatibility. The bioactivity assay was conducted by immersing the samples in SBF solution for 7 and 21 days, and the SEM and XRD surface analyses of the PLA/TCP biocomposites presented evidence of carbonated hydroxyapatite formation. The biocompatibility assay was performed using the extract method until 7 days, and PLA10TCP presented improved relative cell viability compared with the control. Finally, since the materials presented suitable thermal and rheological properties, filaments for additive manufacturing (AM) were developed, and they were used to produce screw models for bone-ligament fixation. The 3D printed screws exhibited excellent printability and accuracy. Therefore, the PLA/TCP biocomposites developed can be used in further biomedical applications using AM, namely, guided bone tissue engineering.     

High molecular weight copolymers of l-lactide and ε-caprolactone as biodegradable elastomeric implant materials

Summary High molecular weight copolymers of L-lactide and -caprolactone have been synthesized by ring opening copolymerization with stannous octoate as catalyst. The good mechanical properties of the 50/50 copolymers make it a suitable material for biomedical applications such as nerve guides etc., where degradation of the elastomeric implant is required. In contrast to the frequently used MDI containing polyurethanes, degradation products of the P(LLA--CL) are non toxic. The use of such a material is therefore preferable.     

Chitosan Fibers Modified with HAp/β-TCP Nanoparticles

This paper describes a method for preparing chitosan fibers modified with hydroxyapatite (HAp), tricalcium phosphate (β-TCP), and HAp/β-TCP nanoparticles. Fiber-grade chitosan derived from the northern shrimp (Pandalus borealis) and nanoparticles of tricalcium phosphate (β-TCP) and hydroxyapatite (HAp) suspended in a diluted chitosan solution were used in the investigation. Diluted chitosan solution containing nanoparticles of Hap/β-TCP was introduced to a 5.16 wt% solution of chitosan in 3.0 wt% acetic acid. The properties of the spinning solutions were examined. Chitosan fibers modified with nanoparticles of HAp/β-TCP were characterized by a level of tenacity and calcium content one hundred times higher than that of regular chitosan fibers.     

Nano grain sized zirconia–silica glass ceramics for dental applications

Glass ceramics based on lithium disilicates are commonly used in dental veneers and crowns. Alternative materials with improved mechanical properties may be of interest for more demanding applications, e.g. bridgeworks. In this study, a sol–gel method was optimized to produce nano grain-sized zirconia–silica glass ceramics with properties adequate for dental applications. The material properties were compared to those of IPS e.max^® CAD, a commercially available lithium disilicate. The zirconia–silica glass ceramic was found to be translucent, with a transmittance of over 70%, and possessed excellent corrosion resistance. It also presented a somewhat lower elastic modulus but higher hardness than the lithium disilicate, and with the proper heat treatment a higher fracture toughness was achieved for the zirconia–silica glass ceramic. In conclusion, the material produced in this study showed promising results for use in dental applications, but the production method is sensitive and large specimen sizes may be difficult to achieve.     

Characterization of sol–gel coated 316L stainless steel for biomedical applications

Silica based organic–inorganic hybrid coatings were deposited on 316L stainless steel by sol–gel technique. The hybrid sols were prepared by hydrolysis and condensation of 3-methacryloxypropyltrimethoxysilane (TMSM) and tetraethylorthosilicate (TEOS) at different molar ratios. Electrochemical experiments were performed to evaluate the corrosion resistance properties of the coatings. Structural characterization of the coatings was performed using scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. Contact angle measurement and cell morphology assay were performed to investigate the hydrophilicity and in vitro cytotoxicity of the coatings, respectively. The results indicate formation of a crack-free and highly adherent film acting as a protective barrier against the physiological medium. Corrosion resistance of hybrid coatings was influenced by the molar ratios of TMSM:TEOS. The best corrosion protection was obtained at TMSM:TEOS molar ratio of 1:1. Sol–gel coatings enhanced the hydrophilicity of 316L steel surfaces. Also, these coatings showed non-toxicity for L929 cells.     

Multicomponent pyrochlore solid solutions with uranium incorporation – A new perspective of materials design for nuclear applications

Multicomponent pyrochlore solid solutions with and without uranium incorporation were fabricated and their thermal-mechanical properties were characterized. Multicomponent pyrochlore solid solutions without uranium exhibit comparable thermal conductivity and higher mechanical strength compared to baseline single component rare-earth titanate pyrochlore (A₂Ti₂O₇). Uranium incorporation reduces hardness as compared with single component compositions. High entropy pyrochlore with uranium displays the highest thermal conductivity within multicomponent pyrochlore solid solutions with significantly better mechanical properties than UO₂. The measured thermal conductivity correlates well with A-site cation mixing entropy and a modified size disorder parameter, and thus the size disorder and mixing entropy could be good indicators for predicting thermal conductivity of multicomponent pyrochlore solid solutions. This work opens up the possibility of designing multicomponent oxide solid solutions by controlling their chemical disorder/mixing entropy to achieve acceptable thermal-mechanical properties, desired radiation and corrosion performance for potential nuclear waste form and inert matrix fuel applications.     

Diamond-ceramics composites—New materials for a wide range of challenging applications

Materials with enhanced wear resistance are of great interest for modern industry. The different ways of producing superhard ceramic materials are shortly reviewed. In detail, the preparation of diamond–silicon carbide composites by reactive infiltration of diamond preforms with liquid silicon at ambient pressure is investigated. In addition to homogeneous SiC/diamond materials with nearly 50 vol.% of diamond layered composites were also prepared. The microstructures of the materials prepared under different infiltration conditions were analyzed using X-ray diffraction, electron microscopy, electron back-scatter diffraction (EBSD) and Raman spectroscopy. The properties of the materials depend strongly on the formation of graphite interlayers at the boundary between SiC and diamond. Hardness of 47 GPa was reached for materials where the formation of the interlayer was prevented.     

Synthesis and characterization of cellulose nanowhisker-reinforced-poly(ε-caprolactone) scaffold for tissue-engineering applications

Poly(ε-caprolactone) (PCL) is a bioresorbable and biocompatible polymer with assorted medical applications. However, remarkable hydrophobicity and nonosteoconductivity have stood as a barrier to limit its applications. The present study aims to modify the bulk characteristics of PCL to develop a polymeric scaffold with adequate structural and mechanical properties to support regenerated tissues. For this purpose, functionalized bacterial cellulose nanowhiskers (BCNW-g-βCD-PCL₂₀₀₀) are synthesized. Reinforcing PCL matrix with 4 wt % of the nanowhiskers resulted in a bionanocomposite with promoted bulk properties. Compared to neat PCL, the obtained bionanocomposite shows improvements of 115 and 51% in tensile strength and Young's modulus, respectively; 20% increase in hydrophilicity; 7% increase in degradation rate; and 6% decrease in crystallinity. Gas foaming/combined particulate leaching technique is used to develop highly porous structures of 86–95% porosity with interconnected macropores of mean pore diameters of 250–420 μm. Porous scaffolds showed compression modulus values of 5.3–9.1 MPa and would have promising applications in regenerative medicine. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48481.     

Bio-cellular glass–ceramic composite with embedded calcium phosphate from eggshell for alternative biomaterials in medical and dental applications

Green biomaterial foams with nontoxicity, low weight, low density, and high-compressive strength, which can be easily manufactured at low cost, are urgently sought. When implanted as a scaffold, bio-cellular glass–ceramic composite has potential for bone bonding, connective tissue growth, and reconstruction of lost tissue. The present study investigates the physical-thermo-mechanical properties of bio-cellular glass–ceramic composite supplemented with calcium phosphate from eggshell powder (0, 1, 3, or 5 wt%) and sodium-silicate binder. The composite materials were prepared by hand pressing and fired at 800 or 900°C for 1 h. The composites containing 1 and 3 wt% calcium phosphate from eggshell powder and fired at 800°C achieved suitable porosity (74–79%), pore size (20–800 μm), bulk density (0.57–0.70 g/cm³), true density (0.98–1.06 g/cm³), water absorption (10.31–21.41%), compressive strength (2.71–3.23 MPa), and thermal expansion coefficient ([5.95–5.98] × 10⁻⁶°C⁻¹) for practical applications. The obtained bio-cellular glass–ceramic composite is an alternative biomaterial for biomedical and dental applications.     

Reduced graphene oxide anchored with δ-MnO2 nanoscrolls as anode materials for enhanced Li-ion storage

We developed a one-pot in situ synthesis procedure to form nanocomposite of reduced graphene oxide (RGO) sheets anchored with 1D δ-MnO₂ nanoscrolls for Li-ion batteries. The as-prepared products were characterized by X-ray diffraction (XRD), Raman spectra, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM). The electrochemical performance of the δ-MnO₂ nanoscrolls/RGO composite was measured by galvanostatic charge/discharge cycling and electrochemical impedance spectroscopy. The results show that the δ-MnO₂ nanoscrolls/RGO composite displays superior Li-ion battery performance with large reversible capacity and high rate capability. The first discharge and charge capacities are 1520 and 810 mAh g⁻¹, respectively. After 50 cycles, the reversible discharge capacity is still maintained at 528 mAh g⁻¹ at the current density of 100 mAh g⁻¹. The excellent electrochemical performance is attributed to the unique nanostructure of the δ-MnO₂ nanoscrolls/RGO composite, the high capacity of MnO₂ and superior electrical conductivity of RGO.     

Hybrid organic–inorganic materials as coatings for protecting wood

A new coating based on organic–inorganic materials was prepared using concurrent sol–gel and polymerization techniques, and applied to wood using a dip coating method. Vinyl-functionalized zirconium oxoclusters were co-polymerized with vinyltrimethoxysilane on wood. The coating process was examined, also assessing the specific weight of hybrid polymer left on the wood after one or two coating steps. The efficacy of the process in consolidating and protecting the wood was investigated using high-temperature differential scanning calorimetry (DSC), environmental scanning electron microscopy (ESEM), infrared spectroscopy and solid state NMR spectroscopy. The coating did not affect the morphology and appearance of the wood. However, it did modify its behavior on exposure to fire and preliminary accelerated biological tests with the brown rot fungus Coniophora puteana showing an improved resistance to the fungal attack.     

Comparative ion-exchange characterization of zeolitic and clayey materials for pedotechnical applications—Part 2: interaction with nutrient cations

With the purpose to evaluate the possible use of a phillipsite-rich tuff, in place of the naturally occurring clay minerals, as inorganic ion-exchanger component of organo-mineral aggregates of pedotechnical interest, the ion-exchange behavior of Neapolitan yellow tuff and a reference montmorillonite-rich material towards some nutrient cations was investigated. Accordingly, exchange kinetics and isotherms of Na⁺, K⁺, and NH₄ ⁺ for Ca²⁺, at 25 °C and 0.1 total normality, were determined, and the related kinetic and thermodynamic quantities computed. The obtained results point out that the zeolitic material, apart from a higher cation exchange capability, exhibits selectivity performances towards nutrient cations comparable or even better than those of the montmorillonitic material, confirming, on the basis of the previous data concerning noxious cations, that phillipsite-rich tuffs can be considered potential substitutes of clay materials to recover and/or rebuild polluted and degraded soils.     

MCMB–SiC composites; new class high-temperature structural materials for aerospace applications

Graphite–silicon carbide (G–SiC), carbon/carbon–silicon carbide (C/C–SiC) and mesocarbon microbeads–silicon carbide (MCMB–SiC) composites were produced using liquid silicon infiltration (LSI) method and their physical and mechanical properties, including density, porosity, flexural strength and ablation resistance were investigated. In comparison with G–SiC and C/C–SiC composites, MCMB–SiC composites have the highest bending strength (210 MPa) and ablation resistance (9.1%). Moreover, scanning electron microscopy (SEM) and optical microscopy (OM) are used to analyze the reacted microstructure, pore morphology and pore distribution of carbon-based matrices. As a result, SiC network reinforcement was formed in situ via a reaction between liquid silicon and carbon. The unreacted carbon and solidified silicon are two phases present in the final microstructure and are characterized by X-ray diffraction (XRD). Based on the results obtained and the low-cost processing of pitch-based materials, the MCMB–SiC composite is a promising candidate for aerospace applications.     

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.     

A single-step polymerization method for poly(β-amino ester) biodegradable hydrogels

A novel one-step method for the preparation of poly(β-amino ester) hydrogels has been developed. The one-step method utilizes a Michael type addition reaction between a difunctional diacrylate and a tetrafunctional primary diamine to create a crosslinked biodegradable hydrogel. It was shown that the molar ratio of the reactive acrylate to amine controlled the extent of polymerization and crosslinking density of the hydrogel system, which enabled for the end properties of the network (e.g., swelling, degradation, and mechanical) to be tuned.     

A novel foam-like silane modified alumina scaffold coated with nano-hydroxyapatite–poly(ε-caprolactone fumarate) composite layer

Although alumina scaffolds with biodegradable polymer coating can overcome the limitations of conventional ceramic bone substitutes, the bioactivity potential of these scaffolds needs to be enhanced. In this study, the macroporous alumina scaffolds with the defined pore-channel interconnectivity were successfully prepared by the foam replication method. The average pore size of the scaffolds was in the range 200–900 μm with around 82% porosity. The average Young's modulus of alumina scaffolds was 2.8 GPa. Coating of nano-hydroxyapatite (nano-HA) in poly(ε-caprolactone fumarate) (PCLF) as a carrier on the surface of alumina scaffold was performed. The nano-HA powder was synthesized successfully by the sol–gel method. The crystallite and particle sizes of HA powders were in nano range and confirmed by the Scherrer equation from X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The PCLF was synthesized and characterized by fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). In order to make a chemical link between the alumina scaffolds and the coating, a silane coupling agent was used. The results showed that using of 1 g Methacryloxypropyl trimethoxysilane in 100 g solvent is sufficient for making a thin interface layer between the scaffold and the polymer. The coating process was performed by immersion of scaffolds in the solutions with different percents of nano-HA. The morphology and chemical structure of the coated scaffolds were investigated by SEM and FTIR. SEM images demonstrated that the scaffolds were constituted of interconnected and homogeneously distributed pores. Also, HA distribution and agglomerates on the surface of scaffolds were enhanced by increasing the nano-HA percent in the coating solutions.     

PCL/β-AgVO3 nanocomposites obtained by solvent casting as potential antimicrobial biomaterials

The adhesion of microorganisms on biomaterials can impair its effective application. The addition of antimicrobial agents is a promising alternative to overcome this limitation. In this work, films of polycaprolactone (PCL) and nanostructured β-AgVO₃ (SV) were produced by solvent casting with 0.1, 0.5, and 1.0 wt% of SV. The effect of SV on the structure of PCL was investigate using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Raman spectroscopy, differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). The antimicrobial activity of the films against Staphylococcus aureus and Escherichia coli was evaluated by the agar diffusion method and by direct contact test. FTIR confirmed the presence of SV into the PCL films, with chemical interaction between them. SEM showed that SV nanorods were well dispersed and with good interfacial adhesion with PCL. XRD diffraction and Raman spectroscopy showed that the presence of SV increased the number of nucleation sites, reducing the size of crystallites and increasing the amorphous domains in the PCL matrix, consequently reducing crystallinity. This behavior was confirmed by DSC, which showed a reduction in the crystallinity with increasing SV content. Films with 1 wt% of SV showed antimicrobial activity against Staphylococcus aureus in direct contact test.