Tubular Matrix Research Articles

Solidification characteristics and microstructure of TaNbZrTi refractory high entropy coating by extreme high-speed laser cladding

Extreme high-speed laser cladding (EHLC) has shown potential in producing refractory high entropy alloy (RHEA) coatings with excellent forming quality. However, there is a lack of theoretical guidance for the EHLC process, and the traditional heat source model is unsuitable. In this study, the laser-molten metal composite heat source model was improved based on the characteristics of EHLC, and a temperature field model suitable for EHLC tubular matrix surface was established and verified by infrared thermal imaging. The solidification characteristics and microstructure of TaNbZrTi RHEA coating prepared by laser cladding (LC), high-speed laser cladding (HLC), and EHLC were compared through temperature field simulation and experimental characterization. The results indicate that the cooling rate of molten pool increases significantly with the increase of scanning speed. EHLC coating has higher cladding efficiency, lower heat accumulation and dilution rate, and denser grain structure compared to LC and HLC coatings. TaNbZrTi coating exhibits a BCC1 + BCC2 phase structure, and the hardness of LC, HLC, and EHLC coating is 577.5, 487.8, and 545.2 HV0.3, respectively. This study provides a simulation model and process guidance for the preparation of TaNbZrTi RHEA coatings.

Architecturally robust tubular nano-clay grafted Li0.9Ni0.5Co0.5O2-x/LiFeO2 nanocomposites: New implications for electrochemical hydrogen storage

To meet the demand for sustainable energy development, focusing on storage systems of clean energy like hydrogen is a priority. However, the utilization of new sorbent materials for an in-depth understanding of hydrogen storage mechanisms remains lacking. Herein, a novel composite electrode based on halloysite nanotube-Li0.9Ni0.5Co0.5O2-x/LiFeO2 (HNT-LNCO/LFO) nanostructures with superior electrochemical hydrogen storage behavior is developed via two-pot synthesis strategy, in which the HNT bridges with rich active sites serve as a natural clay support for LNCO/LFO electrocatalysts to equip improved hydrogen sorption kinetics through the spillover phenomena and redox coupling effect. Varied parameters, such as fuel types, the molar ratio of fuel to nitrates, the concentration of the LNCO/LFO (mg/ml), and solvent were optimized to prepare HNT-LNCO/LFO nanocomposites with desired purity, structure, and morphology. These physicochemical changes were realized by a combination of X-ray Powder Diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), High Resolution Transmission Electron Microscopy (HR-TEM), and Brunauer-Emmett-Teller (BET) analyses. Furthermore, the electrochemical nature of the proposed nanocomposites were probed by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and chronopotentiometry charge–discharge (CCD) process in KOH medium. The effect of conductive LNCO/LFO contents (3.0 %, 5.0 % and 7.0 %) on the HNT substrate was evaluated with the discharge efficiency and hydrogen spillover mechanism. As a consequence, the LNCO/LFO nanoparticles and pristine HNT structures exhibited the hydrogen storage capacities of 499.67 and 84.05 mAhg−1 after 15 cycles, respectively. However, the contribution of LNCO/LFO nanoparticles with weight percent of 3.0 %, 5.0 % and 7.0 % in tubular matrix can produce the discharge efficiencies of 309.33, 437.34 and 132.25 mAhg−1 in three electrode cells, respectively. This systematic work will result in alternative insights of the well-designed HNT-based nanocomposites for highly efficient energy storage applications.

Biomimetic Tubular Matrix Induces Periodontal Ligament Principal Fiber Formation and Inhibits Osteogenic Differentiation of Periodontal Ligament Stem Cells.

Periodontal ligament (PDL) is assembled from highly organized collagen fiber bundles (PDL principal fibers) that are crucial in supporting teeth and buffering mechanical force. Therefore, regeneration of PDL needs to reconstruct these well-ordered fiber bundles to restore PDL functions. However, the formation of PDL principal fibers has long been a challenge due to the absence of an effective three-dimensional (3D) matrix to guide the growth of periodontal ligament stem cells (PDLSCs) and to inhibit the osteogenic differentiation of PDLSCs during the PDL principal fibers deposition. In this work, we designed and fabricated a bio-inspired tubular 3D matrix to guide the migration and growth of human PDLSCs and form well-aligned PDL principal fibers. As a biomimetic 3D template, the tubular matrix controlled PDLSCs migration inside the tubules and aligned the cells to the designated direction. Inside the tubular matrix, the PDLSCs expressed PDL markers and formed oriented fiber bundles with the same size and density as those of natural PDL principal fibers. Furthermore, the tubular matrix downregulated the osteogenic differentiation of PDLSCs. A mechanism study revealed that the Yap1/Twist1 signaling pathway was involved in the inhibition of PDLSCs osteogenesis within the tubular matrix. This work provides an effective approach to induce PDLSCs to form principal fibers and gives insight into the underlying mechanism of inhibiting the osteogenic differentiation of PDLSCs in biomimetic tubular matrices.

Super resolution microscopy and deep learning identify Zika virus reorganization of the endoplasmic reticulum

The endoplasmic reticulum (ER) is a complex subcellular organelle composed of diverse structures such as tubules, sheets and tubular matrices. Flaviviruses such as Zika virus (ZIKV) induce reorganization of ER membranes to facilitate viral replication. Here, using 3D super resolution microscopy, ZIKV infection is shown to induce the formation of dense tubular matrices associated with viral replication in the central ER. Viral non-structural proteins NS4B and NS2B associate with replication complexes within the ZIKV-induced tubular matrix and exhibit distinct ER distributions outside this central ER region. Deep neural networks trained to distinguish ZIKV-infected versus mock-infected cells successfully identified ZIKV-induced central ER tubular matrices as a determinant of viral infection. Super resolution microscopy and deep learning are therefore able to identify and localize morphological features of the ER and allow for better understanding of how ER morphology changes due to viral infection.

Perovskite CoTiO3/TiO2 hybrid nanotubes synthesis via pulsed anodization for photoelectrochemical application

Herein, for the first time hybrid perovskite CoTiO3/TiO2 nanotubes have been synthesized by a simple pulsed anodization process. The conventional Ti anodization electrolyte has been modified with Co2+ cations. The key to the hybrid nanotubes formation lies in the pulsed biasing instead of continuous one. The positive voltage cycle helps forming nanotubes due to Ti oxidation/ dissolution and the negative cycle simultaneously assists Co2+ in the tubular matrix in a controllable manner. The heat treatment in Ar flow transformed the amorphous matrix into CoTiO3/TiO2 heterojunction resulting in a significant photocurrent under simulated sunlight which is 5 and 10 fold as compared to the conventional TiO2 nanotubes and hybrid nanotubes heated in air at the same temperature, respectively. The simple process presented in the current work can be helpful in synthesizing perovskite or metal oxide hybrid nanotubes applied in photocatalysis and renewable energy applications.

Fast Super-Resolution Imaging Technique and Immediate Early Nanostructure Capturing by a Photoconvertible Fluorescent Protein.

Low temporal resolution and limited photocontrollable fluorescent protein probes have restricted the widespread application of single-molecule localization microscopy (SMLM). In the current study, we developed a new photoconvertible fluorescent protein (PCFP), pcStar, and quick single molecule-guided Bayesian localization microscopy (Quick-SIMBA). The combination of pcStar and Quick-SIMBA achieved the highest temporal resolution (0.1-0.25 s) with large field-of-view (76 × 9.4 μm2 -76 × 31.4 μm2) among the SMLM methods, which enabled the dynamic movements of the endoplasmic reticulum dense tubular matrix to be resolved. Moreover, pcStar extended the application of SMLM to imaging the immediate early nanostructures in Drosophila embryos and revealed a specific "parallel three-pillar" structure in the neuronal-glial cell junction, helping to elucidate glial cell "locking" and support of neurons during Drosophila embryogenesis.

Sorption of Strontium Ions on Potassium-Titanate Nanoparticles of Various Morphology Obtained under Hydrothermal Conditions

The results of the study of the interaction of an aqueous solution of strontium nitrate with potas-sium-titanate nanoparticles of different morphology obtained by the hydrothermal method are reported. Comparative analysis showed the advantage of nanotubes as sorbents over nanolayers and nanowires. As can be seen from the experiment conducted with nanotubes containing aluminum, an amount of strontium sorbed from the solution rises with increasing temperature: at 50°C the absorption by the tubular matrix was ≈ 0.76 × 10−3 mol g−1, and at 80°C that was ≈ 2.02 × 10−3 mol g−1. Nanotube samples doped with magnesium had the best sorption characteristics: After 5 h of keeping in a solution at 80°С, the content of strontium in them was ≈3.65 × 10−3 mol g−1. The results show the promise of using potassium titanate nanoparticles to extract strontium from aqueous solutions.

Composite Porous Tubular Biopolymer Matrix of Small Diameter

One of the main problems in cardiovascular surgery is the lack of functionally reliable small-diameter (no more than 4 mm) vascular grafts required for coronary artery bypass grafting and peripheral artery and vein bypass grafting. The purpose of this work is the development of a composite biopolymer porous tubular matrix (CPTB matrix) 2 and 4 mm in diameter with adjustable resorption time and physicomechanical properties close to native blood vessels of the same diameter. The specimens of CPTB matrices with a diameter of 2 and 4 mm were produced by means of electrospinning from poly(hydroxybutyrate-co-hydroxyvalerate) and gelatin solution in hexafluoroisopropanol. The matrix structure was stabilized by treatment with glutaraldehyde (HA) vapor. It was demonstrated that the best specimen in terms of structure, physicomechanical properties, and resorption rate is the matrix obtained with the ratio of poly(hydroxybutyrate-co-hydroxyvalerate) : gelatin equal to 1 : 2 v/v in the solution and additionally crosslinked in HA vapor for 48 h. The detected slight cytotoxicity of the CBPT matrices developed is easily eliminated by treatment with an aqueous solution containing a set of amino acids. Decreasing the diameter of the substrate rod from 4 to 2 mm is accompanied by small changes in the surface structure and the physicomechanical properties of the CPTB matrix.

Композитный пористый трубчатый биополимерный матрикс малого диаметра

Композитный пористый трубчатый биополимерный матрикс малого диаметра

Effects of melatonin oral treatment in pristane-induced lupus nephritis mice

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by lymphocytes hyperactivity and excessive production of pathogenic autoantibodies, pro-inflammatory cytokines and also reactive oxygen species [1]. One of the most severe manifestations of SLE is lupus nephritis (LN), which is characterized by glomerulonephritis and tubulointerstitial inflammation and oxidative stress with also immune-complexes depositing in the renal tissue [2]. Recent evidences suggest that the use of antioxidants in the treatment of LN have satisfactory outcomes. Melatonin is a small, highly conserved pineal indoleamine and due to its important and well known antioxidant and antinflammatory properties [3,4] may be an efficient tool against LN damages. In this study, pristane-induced LN mice were used to investigate the potential protective role of melatonin. At the end of the treatments, the LN animal model presented marked changes in the kidney cytoarchitecture (like glomerular sclerosis, marked tubular degeneration and matrix mesangial expansion) together with significative kidney inflammation, oxidative stress and fibrosis. Interestingly, pristane-mice treated orally with melatonin showed a significative reduction of inflammation, oxidative stress and fibrosis and also of morphological changes at both tubules and glomerular level. In summary, we thought that melatonin may be a potential tool in the management of SLE-glomerulonephritis. Flamma S.p.A.-Italy (www.flammagroup.com) provided with melatonin. Thanks to Fondazione Cariplo e Regione Lombardia “New opportunities and ways towards ERC” (Project 2014-2256) for the grant support.

Dentine-pulp tissue engineering in miniature swine teeth by set calcium silicate containing bioactive molecules

Objective: The present study aims to investigate whether reparative dentinogenesis could be guided at central pulpal sites or at a distance from the amputated pulp of miniature pig teeth, by using set calcium silicate-based carriers containing human recombinant bioactive molecules. DesignPulp exposures were performed in 72 permanent teeth of 4 healthy miniature swine. The teeth were capped with pre-manufactured implants of set calcium silicate-based material containing BMP-7, TGFβ1 or WnT-1, for 3 weeks. Conical-shaped intrapulpal implants were exposed in the central pulp core, while disc-shaped extrapulpal implants were placed at a distance from the amputated pulp. Implants without bioactive molecules were used as controls. Thickness and forms of new matrix mineralized deposition were assessed histologically at post-operative periods of 3 weeks by light microscopy. ResultsIntrapulpal applications: Calcified structures composed of osteodentine were found in contact with the BMP-7 implants. An inhomogeneous calcified tissue matrix was found around the WnT-1 carriers. A two-zone calcified structure composed of osteodentine and a thicker tubular matrix zone was seen at the TGFβ1 carrier-pulp interface. Extrapulpal applications: The space between WnT-1 implants and pulp periphery had been invaded by soft tissue with traces of calcified foci. Thick calcified structures composed of osteodentine were found surrounding pulp exposure sites in response to application of BMP-7. Spindle-shaped cells associated with atubular calcified matrix or elongated polarized cells associated with tubular dentine-like matrix were found along the cut dentinal walls of the TGFβ1 group. ConclusionThe present experiments indicated that set calcium silicate could be used as carrier for biologically active molecules. TGFβ1 was shown to be an effective bioactive molecule in guiding tertiary dentine formation.

Genipin cross-linked decellularized tracheal tubular matrix for tracheal tissue engineering applications.

Decellularization techniques have been widely used as an alternative strategy for organ reconstruction. This study investigated the mechanical, pro-angiogenic and in vivo biocompatibility properties of decellularized airway matrices cross-linked with genipin. New Zealand rabbit tracheae were decellularized and cross-linked with genipin, a naturally derived agent. The results demonstrated that, a significant (p < 0.05) increase in the secant modulus was computed for the cross-linked tracheae, compared to the decellularized samples. Angiogenic assays demonstrated that decellularized tracheal scaffolds and cross-linked tracheae treated with 1% genipin induce strong in vivo angiogenic responses (CAM analysis). Seven, 15 and 30 days after implantation, decreased (p < 0.01) inflammatory reactions were observed in the xenograft models for the genipin cross-linked tracheae matrices compared with control tracheae, and no increase in the IgM or IgG content was observed in rats. In conclusion, treatment with genipin improves the mechanical properties of decellularized airway matrices without altering the pro-angiogenic properties or eliciting an in vivo inflammatory response.

Development of bi-layer vascular constructs by combining polymer biomaterial and cellular self assembly

Development of bi-layer vascular constructs by combining polymer biomaterial and cellular self assembly

Effect of Oxygen Content on the Photoelectrochemical Activity of Crystallographically Preferred Oriented Porous Ta3N5 Nanotubes

Crystallographically preferred oriented porous Ta3N5 nanotubes (NTs) were synthesized by thermal nitridation of vertically oriented, thick-walled Ta2O5 NTs, strongly adhered to the substrate. The adherence on the substrate and the wall thickness of the Ta2O5 NTs were fine-tuned by anodization, thereby helping to preserve their tubular morphology for nitridation at higher temperatures. Samples were studied by scanning electron microscopy, high-resolution electron microscopy, X-ray diffraction, Rietveld refinements, ultraviolet–visible spectrophotometry, X-ray photoelectron spectroscopy, photoluminescence spectra, and electrochemical techniques. Oxygen content in the structure of porous Ta3N5 NTs strongly influenced their photoelectrochemical activity. Structural analyses revealed that the nitridation temperature has crystallographically controlled the preferential orientation along the (110) direction, reduced the oxygen content in the crystalline structure and the tubular matrix, and increased the grain size. The preferred oriented porous Ta3N5 NTs optimized by the nitridation temperature presented an enhanced photocurrent of 7.4 mA cm–2 at 1.23 V vs RHE under AM 1.5 (1 Sun) illumination. Hydrogen production was evaluated by gas chromatography, resulting in 32.8 μmol of H2 in 1 h from the pristine porous Ta3N5 NTs. Electrochemical impedance spectroscopy has shown an effect of nitridation temperature on the interfacial charge transport resistance at the semiconductor–liquid interface; however, the flat band of Ta3N5 NTs remained unchanged.

Congenital trigger thumb in children

Although numerous studies have been performed on congenital trigger thumb (CTT), the pathogenesis is still unknown. Cytocontractile proteins and myofibroblasts are present during soft-tissue contraction, and they may have a role in CTT. The aim of the study is to clarify the immunohistochemical and the electron microscopy characteristics of the first annular (A-1) pulley in CTT. The specimens from the A-1 pulleys were collected from 22 children with CTT. Electron microscopy was used to study the last five specimens. Immunohistochemistry staining demonstrated that all specimens stained positively for vimentin and for α-smooth muscle actin, and stained negatively for desmin. Electron microscopy showed fibroblasts in collagenous matrix, which contain vimentin-like material and associated at the surface with elastin-like tubular matrix filaments and elastin fibers. In two specimens, a few cells showed markers of myofibroblastic differentiation. The presence of the cytocontractile proteins and myofibroblasts suggests proliferation of fibrous tissues during either the intrauterine or extrauterine phase of development and may account for the presence of congenital stenosis at the level of the A-1 pulley. We believe that CTT may be developmental; if the process started in the intrauterine phase it might present as a fixed flexion contracture and will show mature fibroblasts. If the process started in the extrauterine phase, it might present as triggering first and will show myofibroblastic changes, then with the maturation of the fibrous tissue, result in a fixed flexion contracture.

Preparation of porous polycaprolactone tubular matrix by salt leaching process

AbstractSalt leaching technique has been employed to produce polycaprolactone (PCL) based porous tubular matrix. Salt was dispersed into PCL solution in chloroform and the subsequent leaching of salt was accomplished in water. The effect of salt and polymer concentration on the mechanical properties, porosity and surface characteristics was studied. It was observed that salt concentration has significant influence over crystalline nature of the scaffold. The porous structures became more interconnected as the salt concentration increased. This process yields a tubular porous matrix with maximum porosity of 61%, strength of 1.84 (±0.04) MPa and tensile strain of 120 (±7.94). © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Electrical and optical characteristics of surface treated ZnO nanotubes

Vertical ZnO nanotubes were electrochemically deposited onto an indium doped tin oxide glass substrate. These nanotubes were surface treated with zinc acetate and annealed at 450°C, resulting in a nanotubes/nanoparticles composite layer. Scanning electron microscopy of the surface treated samples showed nanoparticles been dispersed uniformly along the ZnO tubular matrix, which was confirmed by X-ray diffractrometry. Photoluminescence and fluorescence microscopy showed untreated ZnO nanotubes exhibiting blue emission, while the treated samples exhibited green emissions. Ultra-violet spectroscopy of treated samples revealed lower band gap values compare to their untreated counterparts. Lifetime measurements showed higher excitonic lifetimes in treated samples. Conductance studies using atomic force microscopy showed significant improvement in the conductance values for the treated samples. A significant increase in photocurrent was observed in treated samples when used as photo-anodes in dye sensitized solar cells.

Designing a tubular matrix of oriented collagen fibrils for tissue engineering

A scaffold composed entirely of an extracellular matrix component, such as collagen, with cellular level control would be highly desirable for applications in tissue engineering. In this article we introduce a novel, straightforward flow processing technique that fabricates a small diameter tubular matrix constructed of anisotropic collagen fibrils. Scanning electron microscopy confirmed the uniform alignment of the collagen fibrils and subsequent matrix-induced alignment of human fibroblasts. The uniform alignment of the fibroblasts along the collagen fibrils demonstrated the ability of the aligned fibrils to successfully dictate the directional growth of human fibroblasts through contact guidance. Various non-cytotoxic cross-linking techniques were also applied to the collagen conduit to enhance the mechanical properties. Tensile testing and burst pressure were the two measurements performed to characterize the mechanical integrity of the conduit. Mechanical characterization of the cross-linked collagen conduits identified 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide hydrochloride cross-linking as the most promising technique to reinforce the mechanical properties of native collagen. An oriented conduit of biocompatible material has been fabricated with decent mechanical strength and at a small diameter scale, which is especially applicable in engineering cardiovascular tissues and nerve grafts.

The use of dental papillae cells and millipore filter for bioengineered dentin

To observe the ability of SD rat dental papillae cells forming dentin-like structure induced by millipore filter combined with transforming growth factor-β(1) (TGF-β(1)). The first passage SD rat dental papillae cells were enzymatically dissociated and centrifuged to obtain a cell mass. The cell mass was seeded on the millipore filter combined with TGF-β(1). The complex was incubated for 6 d in vitro or transplanted under the renal capsule for 2 weeks. Then the differentiation of dental papillae cells on the filter and the formation of mineral tissue on the implant were analyzed. A layer of polarized columnar cells were observed along the surface of the millipore filter, with cell processes extending into the porous media. Dentin sialoprotein (DSP) and dentin matrix protein-1 (DMP-1) were positive in these cells. After 2 weeks, tubular dentin matrix was deposited on the surface of the aligned cells. Scanning electron microscopy showed that the thickness of newly formed tubular dentin was consistent. DSP and DMP-1 were expressed in columnar cells, tubular matrix and the dental papillae cells adjacent to the filter. The millipore filter combined with TGF-β(1) could effectively recruit progenitors onto its surface and induce odontoblast differentiation, secrete matrix in a homogenous manner, leading to dentinogenesis.

High Density Collagen Tubes for Tissue Engineering of Ureteral and Urethral Structures

Purpose Ureteral and urethral structures need to be replaced in several congenital and acquired diseases. Tissue engineered structures might be a solution for replacing diseased or missing tubular structures of the urinary tract. Collagen, the most abundant protein in mammals, gives structure, consistency and resistance to soft tissues and might act as adequate scaffold to engineer such tissue constructs. Material and Methods We designed a novel method to obtain a cell-seeded tubular scaffold, based on collagen gel submitted to a process of plastic compression. We specifically investigated their mechanical properties, and their aptitude for human bladder smooth muscle cell growth was evaluated by histology and electron microscopy. Results The resulting construct has a particularly high collagen density and is characterized by very promising mechanical properties regarding burst pressure and water tightness, which makes it an attractive candidate for tissue engineering of ureteral and urethral structures. Seeding density of 106 smooth muscle cells per 300ml gel gives a more than 25-fold increase of the cell population within the tubes after two weeks in culture. The histology of the three-dimensional smooth muscle cell growth within the tubular matrix is demonstrated and electron microscopy analysis of the construct discussed. The results of such tubes, further seeded with human urothelial cells and cultured in a flow bioreactor system, will be discussed. Conclusions The plastic compressed collagen gel tubes are easy-to-produce, readily cell-seeded matrices. The reported results clearly set plastic compressed collagen gel tubes as suitable scaffolds for tissue engineering of tubular structures of the human urinary tract. Ureteral and urethral structures need to be replaced in several congenital and acquired diseases. Tissue engineered structures might be a solution for replacing diseased or missing tubular structures of the urinary tract. Collagen, the most abundant protein in mammals, gives structure, consistency and resistance to soft tissues and might act as adequate scaffold to engineer such tissue constructs. We designed a novel method to obtain a cell-seeded tubular scaffold, based on collagen gel submitted to a process of plastic compression. We specifically investigated their mechanical properties, and their aptitude for human bladder smooth muscle cell growth was evaluated by histology and electron microscopy. The resulting construct has a particularly high collagen density and is characterized by very promising mechanical properties regarding burst pressure and water tightness, which makes it an attractive candidate for tissue engineering of ureteral and urethral structures. Seeding density of 106 smooth muscle cells per 300ml gel gives a more than 25-fold increase of the cell population within the tubes after two weeks in culture. The histology of the three-dimensional smooth muscle cell growth within the tubular matrix is demonstrated and electron microscopy analysis of the construct discussed. The results of such tubes, further seeded with human urothelial cells and cultured in a flow bioreactor system, will be discussed. The plastic compressed collagen gel tubes are easy-to-produce, readily cell-seeded matrices. The reported results clearly set plastic compressed collagen gel tubes as suitable scaffolds for tissue engineering of tubular structures of the human urinary tract.