A Direct Electric Field-Aided Biomimetic Mineralization System for Inducing the Remineralization of Dentin Collagen Matrix

This in vitro study aimed to accelerate the remineralization of a completely demineralized dentine collagen block in order to regenerate the dentinal microstructure of calcified collagen fibrils by a novel electric field-aided biomimetic mineralization system in the absence of non-collagenous proteins. Completely demineralized human dentine slices were prepared using ethylene diamine tetraacetic acid (EDTA) and treated with guanidine hydrochloride to extract the bound non-collagenous proteins. The completely demineralized dentine collagen blocks were then remineralized in a calcium chloride agarose hydrogel and a sodium hydrogen phosphate and fluoride agarose hydrogel. This process was accelerated by subjecting the hydrogels to electrophoresis at 20 mA for 4 and 12 h. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM) were used to evaluate the resultant calcification of the dentin collagen matrix. SEM indicated that mineral particles were precipitated on the intertubular dentin collagen matrix; these densely packed crystals mimicked the structure of the original mineralized dentin. However, the dentinal tubules were not occluded by the mineral crystals. XRD and EDX both confirmed that the deposited crystals were fluorinated hydroxyapatite. TEM revealed the existence of intrafibrillar and interfibrillar mineralization of the collagen fibrils. A novel electric field-aided biomimetic mineralization system was successfully developed to remineralize a completely demineralized dentine collagen matrix in the absence of non-collagenous proteins. This study developed an accelerated biomimetic mineralization system which can be a potential protocol for the biomineralization of dentinal defects.     

Bioconjugation Strategy for Ceramic Membranes Decorated with Candida Antarctica Lipase B—Impact of Immobilization Process on Material Features

A strategy for the bioconjugation of the enzyme Candida antarctica lipase B onto titania ceramic membranes with varied pore sizes (15, 50, 150, and 300 kDa) was successfully performed. The relationship between the membrane morphology, i.e.,the pore size of the ceramic support, and bioconjugation performance was considered. Owing to the dimension of the enzyme (~33 kDa), the morphology of the ceramics allowed (50, 150, and 300 kDa) or did not allow (15 kDa) the entrance of the enzyme molecules into the porous structure. Such a strategy made it possible to better understand the changes in the material (morphology) and physicochemical features (wettability, adhesiveness, and surface charge) of the samples, which were systematically examined. The silane functionalization and enzyme immobilization were accomplished via the covalent route. The samples were characterized after each stage of the modification, which was very informative from the material point of view. As a consequence of the modification, significant changes in the contact angle, roughness, adhesion, and zeta potential were observed. For instance, for the 50 kDa membrane, the contact angle increased from 29.1 ± 1.5° for the pristine sample to 72.3 ± 1.5° after silane attachment; subsequently, it was reduced to 57.2 ± 1.5° after the enzyme immobilization. Finally, the contact angle of the bioconjugated membrane used in the enzymatic process rose to 92.9 ± 1.5°. By roughness (S_q) controlling, the following amendments were noticed: for the pristine 50 kDa membrane, S_q = 1.87 ± 0.21 µm; after silanization, S_q = 2.33 ± 0.30 µm; after enzyme immobilization, S_q = 2.74 ± 0.26 µm; and eventually, after the enzymatic process, S_q = 2.37 ± 0.27 µm. The adhesion work of the 50 kDa samples was equal to 136.41 ± 2.20 mN m⁻¹ (pristine membrane), 94.93 ± 2.00 mN m⁻¹ (with silane), 112.24 ± 1.90 mN m⁻¹ (with silane and enzyme), and finally, 69.12 ± 1.40 mN m⁻¹ (after the enzymatic process). The materials and physicochemical features changed substantially, particularly after the application of the membrane in the enzymatic process. Moreover, the impact of ceramic material morphology on the zeta potential value is here presented for the first time. With an increase in the ceramic support cut-off, the amount of immobilized lipase rose, but the specific productivity was higher for membranes possessing smaller pores, owing to the higher grafting density. For the enzymatic process, two modes of accomplishment were selected, i.e., stirred-tank and cross-flow. The latter method was characterized by a much higher effectiveness, with a resulting productivity equal to 99.7 and 60.3 µmol h⁻¹ for the 300 and 15 kD membranes, respectively.     

Silica- Iron Oxide Nanocomposite Enhanced with Porogen Agent Used for Arsenic Removal

This study aims to remove arsenic from an aqueous medium by adsorption on a nanocomposite material obtained by the sol–gel method starting from matrices of silica, iron oxide and NaF (SiO₂/Fe(acac)₃/NaF). Initially, the study focused on the synthesis and characterization of the material by physico–chemical methods such as: X-ray diffraction, FT-IR spectroscopy, Raman spectroscopy, atomic force microscopy, and magnetization. Textural properties were obtained using nitrogen adsorption/desorption measurements. The zero load point, pHpZc, was also determined by the method of bringing the studied system into equilibrium. In addition, this study also provides a comprehensive discussion of the mechanism of arsenic adsorption by conducting kinetic, thermodynamic and equilibrium studies. Studies have been performed to determine the effects of adsorbent dose, pH and initial concentration of arsenic solution, material/arsenic contact time and temperature on adsorption capacity and material efficiency. Three theoretical adsorption isotherms were used, namely Langmuir, Freundlich and Sips, to describe the experimental results. The Sips isotherm was found to best describe the experimental data obtained, the maximum adsorption capacity being ~575 µg As(III)/g. The adsorption process was best described by pseudo-second order kinetics. Studies have been performed at different pH values to establish not only the optimal pH at which the adsorption capacity is maximum, but also which is the predominantly adsorbed species. The effect of pH and desorption studies have shown that ion exchange and the physiosorption mechanism are implicated in the adsorption process. From a thermodynamic point of view, parameters such as ΔG°, ΔH° and ΔS° were evaluated to establish the mechanism of the adsorption process. Desorption studies have been performed to determine the efficiency of the material and it has been shown that the material can be used successfully to treat a real-world example of deep water with a high arsenic content.     

Synthesis of Ni/Y2O3 Nanocomposite through USP and Lyophilisation for Possible Use as Coating

The Ni/Y₂O₃ catalyst showed high catalytic activity. Based on this, the aim of this study was to create Ni/Y₂O₃ nanocomposites powder with two innovative technologies, Ultrasonic Spray Pyrolysis (USP) and lyophilisation. In the USP process, thermal decomposition of the generated aerosols in an N₂/H₂ reduction atmosphere caused a complete decomposition of the nickel (II) nitrate to elemental Ni, which became trapped on the formed Y₂O₃ nanoparticles. The Ni/Y₂O₃ nanocomposite particles were captured via gas washing in an aqueous solution of polyvinylpyrrolidone (PVP) in collection bottles. PVP was chosen for its ability to stabilise nano-suspensions and as an effective cryoprotectant. Consequently, there was no loss or agglomeration of Ni/Y₂O₃ nanocomposite material during the lyophilisation process. The Ni/Y₂O₃ nanocomposite powder was analysed using ICP-MS, SEM-EDX, and XPS, which showed the impact of different precursor concentrations on the final Ni/Y₂O₃ nanocomposite particle composition. In a final step, highly concentrated Ni/Y₂O₃ nanocomposite ink (Ni/Y₂O₃ > 0.140 g/mL) and test coatings from this ink were prepared by applying them on a white matte photo paper sheet. The reflection curve of the prepared Ni/Y₂O₃ nanocomposite coating showed a local maximum at 440 nm with a value of 39% reflection. Given that Ni is located on the surface of the Ni/Y₂O₃ nanocomposite in the elemental state and according to the identified properties, tests of the catalytic properties of this coating will be performed in the future.     

Bone Density Micro-CT Assessment during Embedding of the Innovative Multi-Spiked Connecting Scaffold in Periarticular Bone to Elaborate a Validated Numerical Model for Designing Biomimetic Fixation of Resurfacing Endoprostheses

Our team has been working for some time on designing a new kind of biomimetic fixation of resurfacing endoprostheses, in which the innovative multi-spiked connecting scaffold (MSC-Scaffold) that mimics the natural interface between articular cartilage and periarticular trabecular bone in human joints is the crucial element. This work aimed to develop a numerical model enabling the design of the considered joint replacement implant that would reflect the mechanics of interacting biomaterials. Thus, quantitative micro-CT analysis of density distribution in bone material during the embedding of MSC-Scaffold in periarticular bone was applied. The performed numerical studies and corresponding mechanical tests revealed, under the embedded MSC-Scaffold, the bone material densification affecting its mechanical properties. On the basis of these findings, the built numerical model was modified by applying a simulated insert of densified bone material. This modification led to a strong correlation between the re-simulation and experimental results (FVU = 0.02). The biomimetism of the MSC-Scaffold prototype that provided physiological load transfer from implant to bone was confirmed based on the Huber–von Mises–Hencky (HMH) stress maps obtained with the validated finite element (FE) model of the problem. The micro-CT bone density assessment performed during the embedding of the MSC-Scaffold prototype in periarticular bone provides insight into the mechanical behaviour of the investigated implant-bone system and validates the numerical model that can be used for the design of material and geometric features of a new kind of resurfacing endoprostheses fixation.     

Significance of Serum Type-IV Collagen Levels in Various Liver Diseases Measurement with a One-Step Sandwich Enzyme Immunoassay Using Monoclonal Antibodies with Specificity for Pepsin-Solubilized Type-IV Collagen

Serum type-IV collagen levels determined with a one-step sandwich enzyme immunoassay (EIA) using monoclonal antibodies with specificity for pepsin-solubilized type-IV collagen were compared with histologic changes in liver biopsy specimens from 107 patients with various liver diseases. Serum type-IV collagen levels were increased in the groups with liver diseases compared with controls. The serum type-IV collagen levels in the group with alcoholic cirrhosis showed significantly higher values than the other groups (P < 0.05). A significant positive correlation was found between the serum type-IV collagen level and the degree of fibrosis or cell infiltration in 107 patients. Immunolocalization of type-IV collagen was observed around blood vessels and bile ducts increased in number in the portal tracts, with cell infiltration and fibrosis, increased around vessels in fibrous septa, and sinusoidal walls of areas with cell infiltration or necrosis in hepatic lobules, and along the boundary between fibrous septa and hepatocytes. The present data indicate that serum type-IV collagen may be a sensitive marker for active fibrosis and that the elevation of serum type-IV collagen level primarily reflects the enhancement of type-IV collagen synthesis and deposition in the liver tissue at the stage of active fibrosis in liver disease.     

The Effect of Changes in the Separation Process for the Performance of Recycled Cement Powder: A Comparison with a Previous Study for Radioactive Waste Immobilization

Separation of hydrated cement paste from aggregate is a key technology to reduce the amount of radioactive concrete waste during the decommissioning process. If separated cement-paste portions can be recycled as a solidifying agent for other radioactive waste, the amount of radioactive concrete waste could be close to “zero”. A study was conducted to achieve circular economy in the area of concrete decommissioning and found it to be successfully used as a solidifying agent for immobilization of liquid radioactive waste. However, previous work used a process that requires large amounts of energy (heat treatment was applied to most of the concrete fraction) because the objective was to completely remove hydrated cement powder from the aggregate. In this work, the separation system was modified to increase energy efficiency (heat treatment was applied to separated powder only), but such a change decreased the surface area of the recycled cement powder due to a higher inclusion of aggregate powder. A relatively lower solution to binder ratio could have been achieved for the preparation of wasteform specimens, and as a result, a 28 day compressive strength of wasteform could have become higher, but the final leachability indices were lower than the results observed from previous work. The results from 28 day compressive strength, thermal cycling and 90 day leaching experiments met the acceptance criteria for wasteform, indicating that this modified system can also be used for immobilization of liquid radioactive waste to meet the “zero” production of concrete waste during the decommissioning of a nuclear power plant. It should be noted that accurate monitoring of aggregate content in recycled cement powder during production is important to maintain proper reactivity of recycled cement powder.