Development of a bone substitute material based on alpha-tricalcium phosphate scaffold coated with carbonate apatite/poly-epsilon-caprolactone

In Vitro and In Vivo Bone Regeneration Assessment of Titanium-Doped Waste Eggshell-Derived Hydroxyapatite in the Animal Model

In this work, a titanium-doped hydroxyapatite (HAp) scaffold was produced from two different sources (natural eggshell and laboratory-grade reagents) to compare the efficacy of natural and synthetic resources of HAp materials on new bone regeneration. This comparative study also reports the effect of Ti doping on the physical, mechanical, and in vitro as well as in vivo biological properties of the HAp scaffold. Pellets were prepared in the conventional powder metallurgy route, compacted, and sintered at 900 °C, showing sufficient porosity for bony ingrowth. The physical-mechanical characterizations were performed by density, porosity evaluation, XRD, FTIR, SEM analysis, and hardness measurement. In vitro interactions were evaluated by bactericidal assay, hemolysis, MTT assay, and interaction with simulated body fluid. All categories of pellets showed absolute nonhemolytic and nontoxic character. Furthermore, significant apatite formation was observed on the Ti-doped HAp samples in the simulated body fluid immersion study. The developed porous pellets were implanted to assess the bone defect healing in the femoral condyle of healthy rabbits. A 2 month study after implantation showed no marked inflammatory reaction for any samples. Radiological analysis, histological analysis, SEM analysis, and oxytetracycline labeling studies depicted better invasion of mature osseous tissue in the pores of doped eggshell-derived HAp scaffolds as compared to the undoped HAp, and laboratory-made samples. Quantification using oxytetracycline labeling depicted 59.31 ± 1.89% new bone formation for Ti-doped eggshell HAp as compared to Ti-doped pure HAp (54.41 ± 1.93) and other undoped samples. Histological studies showed the presence of abundant osteoblastic and osteoclastic cells in Ti-doped eggshell HAp in contrast to other samples. Radiological and SEM data also showed similar results. The results indicated that Ti-doped biosourced HAp samples have good biocompatibility, new bone-forming ability, and could be used as a bone grafting material in orthopedic surgery.

Facile bioactive transformation of magnesium alloy surfaces for surgical implant applications

The market for orthopedic implant alloys has seen significant growth in recent years, and efforts to reduce the carbon footprint of medical treatment (i.e., green medicine) have prompted extensive research on biodegradable magnesium-based alloys. Magnesium alloys provide the mechanical strength and biocompatibility required of medical implants; however, they are highly prone to corrosion. In this study, Mg-9Li alloy was immersed in cell culture medium to simulate degradation in the human body, while monitoring the corresponding effects of the reaction products on cells. Variations in pH revealed the generation of hydroxyl groups, which led to cell death. At day-5 of the reaction, a coating of MgCO3 (H2O)3, HA, and α -TCP appeared on sample surfaces. The coating presented three-dimensional surface structures (at nanometer to submicron scales), anti-corrosion effects, and an altered surface micro-environment conducive to the adhesion of osteoblasts. This analysis based on bio-simulation immersion has important implications for the clinical use of Mg alloys to secure regenerated periodontal tissue.

Evaluation of the impact of pH of the reaction mixture, type of the stirring, and the reagents' concentration in the wet precipitation method on physicochemical properties of hydroxyapatite so as to enhance its biomedical application potential

Hydroxyapatite (HAp) constitutes a significant inorganic compound which due to its osteoinductivity, osteoconductivity as well as the ability to promote bone growth and regeneration is widely applied in development of biomaterials designed for bone tissue engineering. In this work, various synthesis methodologies of HAp based on the wet precipitation technique were applied, and the impact of pH of the reaction mixture, the concentration of individual reagents as well as the type of stirring applied (mechanical/magnetic) on the properties of final powders was discussed. Spectroscopic methods (Fourier transform infrared, Raman) and X-ray diffraction allowed to verify the synthesis parameters leading to obtaining calcium phosphate with 96% HAp in phase which indicated higher homogeneity of obtained powder (93.4%) than commercial HAp. Powders' morphology was evaluated using microscopic techniques while specific surface area was determined via Brunauer-Emmett-Teller analysis. Particle size distribution, porosity of powders, and stability of HAp suspensions were also characterized. It was proved that synthesis at pH = 11.0 using mechanical stirring resulted in calcium phosphate with a high phase homogeneity and homogeneous pore size distribution (6-20 nm). Moreover, obtained HAp powder showed 71.8% more specific surface area than commercial material-that is, 110 m³ /g for synthetic HAp and 64 m³ /g in the case of commercial powder-which, in turn, is significant in terms of its potential application as carrier of active substances. Thus it was demonstrated that by applying appropriate conditions of HAp synthesis it is possible to obtain powder with properties enhancing its application potential for medical purposes.

Airbrushed Polysulfone (PSF)/Hydroxyapatite (HA) Nanocomposites: Effect of the Presence of Nanoparticles on Mechanical Behavior

Nanocomposite films of polysulfone (PSF)—hydroxyapatite (HA) were prepared with a commercial airbrush. Structural, thermal, and mechanical characterization allows obtaining new information to understand the role of the nanofiller–polymer matrix interphase in the final performance of these materials in relation to its possible applications in the restoration of bones. Fourier-transform infrared spectroscopy shows that there are hardly any structural changes in the polymer when adding HA particles. From thermal analysis (differential scanning calorimetry and thermogravimetry), it can be highlighted that the presence of HA does not significantly affect the glass transition temperature of the PSF but decelerates its thermal degradation. All this information points out that any change in the PSF performance because of the addition of HA particles cannot be due to specific interactions between the filler and the polymer. Results obtained from uniaxial tensile tests indicate that the addition of small amounts of HA particles (1% wt) leads to elastic moduli higher than the upper bound predicted by the rule of mixtures suggesting there must be a high contribution of the interphase. A simple model of the nanocomposite is proposed for which three contributions must be considered, particles, interphase and matrix, in such a way that interphases arising from different particles can interact by combining with each other thus leading to a decrease in its global contribution when the amount of particles is high enough. The mechanical behavior can be explained considering a balance between the contribution of the interphase and the number of particles. Finally, a particular mechanism is proposed to explain why in certain nanocomposites relatively high concentrations of nanoparticles may substantially increase the strain to failure.

Development and Characterization of Cellulose/Iron Acetate Nanofibers for Bone Tissue Engineering Applications

In tissue engineering, design of biomaterial with a micro/nano structure is an essential step to mimic extracellular matrix (ECM) and to enhance biomineralization as well as cell biocompatibility. Composite polymeric nanofiber with iron particles/ions has an important role in biomineralization and collagen synthesis for bone tissue engineering. Herein, we report development of polymeric cellulose acetate (CA) nanofibers (17 wt.%) and traces of iron acetates salt (0.5 wt.%) within a polymeric solution to form electrospinning nanofibers mats with iron nanoparticles for bone tissue engineering applications. The resulting mats were characterized using field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM), Fourier transform infrared (FTIR), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The resulted morphology indicated that the average diameter of CA decreased after addition of iron from (395 ± 30) to (266 ± 19) nm and had dense fiber distributions that match those of native ECM. Moreover, addition of iron acetate to CA solution resulted in mats that are thermally stable. The initial decomposition temperature was 300 °C of CA/Fe mat > 270 °C of pure CA. Furthermore, a superior apatite formation resulted in a biomineralization test after 3 days of immersion in stimulated environmental condition. In vitro cell culture experiments demonstrated that the CA/Fe mat was biocompatible to human fetal-osteoblast cells (hFOB) with the ability to support the cell attachment and proliferation. These findings suggest that doping traces of iron acetate has a promising role in composite mats designed for bone tissue engineering as simple and economically nanoscale materials. Furthermore, these biomaterials can be used in a potential future application such as drug delivery, cancer treatment, and antibacterial materials.

Performance of two bone substitutes of novel cotton-like β-TCP/PDLGA and granular β-TCP on bone regeneration in the femoral bone defect of the Beagle dogs

This study aimed to clarify whether novel cotton-like composite made of β-tricalcium phosphate (β-TCP) and poly(Dl-lactide-co-glycolide) (PDLGA) has a different effect on in vivo bone regeneration after bone defect than that of granular β-TCP. Five male Beagle dogs served as subjects. Cortical and medullary bone defect as non-through holes were made at the diaphysis of the bilateral femurs. One side was implanted with β-TCP/PDLGA (β-TCP/PDLGA group) and the other side was implanted with granular β-TCP (β-TCP group). At 4 weeks after implantation, we found no significant differences in the percentages of newly formed bone area and fibrous tissue area in the bone defect between the two groups. The β-TCP/PDLGA group showed more uniform filling on the surface and earlier disappearance of the material in the medullary region, and there were fewer inflammatory cells and osteoclasts in the bone defect in the β-TCP/PDLGA group. In conclusion, β-TCP/PDLGA performs better at filling the bone defect uniformly and disappears earlier at the cortical and medullary regions while causing less inflammation and bone resorption. Although bone formation activity of the β-TCP/PDLGA group in the cortical region was lower, the newly formed bone volume in bone defect of the β-TCP/PDLGA group was equal to that of the β-TCP group.

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Novel cotton-like composite made of β-TCP/PDLGA was compared with granular β-TCP.

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Cotton-like β-TCP/PDLGA performed better at filling the bone defect uniformly.

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Cotton-like β-TCP/PDLGA disappeared earlier at the implanted bone regions.

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β-TCP/PDLGA caused less inflammation and bone resorption in the bone defect.

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The newly formed bone volume in bone defect was equal between the two materials.

Chiral Tartaric Acid Improves Fracture Toughness of Bioactive Brushite-Collagen Bone Cements

Brushite cements are promising bone regeneration materials with limited biological and mechanical properties. Here, we engineer a mechanically improved brushite-collagen type I cement with enhanced biological properties by use of chiral chemistry; d- and l-tartaric acid were used to limit crystal growth and increase the mechanical properties of brushite-collagen cements. The impact of the chiral molecules on the cements was examined with Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). A 3-point bend test was utilized to study the fracture toughness, and cell attachment and morphology studies were carried out to demonstrate biocompatibility. XRD and SEM analyses showed that l-, but not d-tartaric acid, significantly restrained brushite crystal growth by binding to the {010} plane of the mineral and increased brushite crystal packing and the collagen interaction area. l-Tartaric acid significantly improved fracture toughness compared to traditional brushite by 30%. Collagen significantly enhanced cell morphology and focal adhesion expression on l-tartaric acid-treated brushite cements.