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Exosomes are extracellular nanovesicles that play an important role in cellular communication. The modulatory effects of bone morphogenetic protein 2 (BMP2) on macrophages have ...encouraged the functionalization of scaffolds through the integration of the exosomes from the BMP2-stimulated macrophages to avoid ectopic bone formation and reduce adverse effects. To determine the functionality of exosomal nanocarriers from macrophages after BMP2 stimulation, we isolated the exosomes from Dulbecco’s modified Eagle’s medium (DMEM)- or BMP2-stimulated macrophages and evaluated their effects on osteogenesis. Morphological characterization of the exosomes derived from DMEM- or BMP2-treated macrophages revealed no significant differences, and the bone marrow-derived mesenchymal stromal cells showed similar cellular uptake patterns for both exosomes. In vitro study using BMP2/macrophage-derived exosomes indicated their beneficial effects on osteogenic differentiation. To improve the bio-functionality for titanium implants, BMP2/macrophage-derived exosomes were used to modify titanium nanotube implants to favor osteogenesis. The incorporation of BMP2/macrophage-derived exosomes dramatically increased the expression of early osteoblastic differentiation markers, alkaline phosphatase (ALP) and BMP2, indicative of the pro-osteogenic role of the titanium nanotubes incorporated with BMP2/macrophage-derived exosomes. The titanium nanotubes functionalized with BMP2/macrophage-derived exosomes activated autophagy during osteogenic differentiation. In conclusion, the exosome-integrated titanium nanotube may serve as an emerging functional material for bone regeneration.
The clinical application of bone morphogenetic protein 2 (BMP2) is often limited by its side effects. Exosomes are naturally secreted nanosized vesicles derived from cells and play an important role in intercellular communication.
The contributions of this study include (1) the demonstration of the potential regulatory role of BMP2/macrophage-derived exosomes on the osteogenic differentiation of mesenchymal stromal cells (MSCs); (2) fabrication of titanium nanotubes incorporated with exosomes; (3) new insights into the application of titanium nanotube-based materials for the safe use of BMP2.
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Implanted biomaterials play a key role in the current success of orthopedic and dental procedures. Pure titanium and its alloys are the most commonly used materials for permanent ...implants in contact with bone. However, implant-related infections remain among the leading reasons for failure. The most critical pathogenic event in the development of infection on biomaterials is biofilm formation, which starts immediately after bacterial adhesion. In the last decade, numerous studies reported the ability of titanium surface modifications and coatings to minimize bacterial adhesion, inhibit biofilm formation and provide effective bacterial killing to protect implanted biomaterials. In the present review, the different strategies to prevent infection onto titanium surfaces are reported: surface modification and coatings by antibiotics, antimicrobial peptides, inorganic antibacterial metal elements and antibacterial polymers.
Implanted biomaterials play a key role in the current success of orthopedic and dental procedures. Pure titanium and its alloys are the most commonly used materials for permanent implants in contact with bone. Microbial infection is one of the main causes of implant failure. Currently, the global infection risk is 2–5% in orthopedic surgery. Numerous solutions exist to render titanium surfaces antibacterial. The LBPS team is an expert on the functionalization of titanium surfaces by using bioactive polymers to improve the biologiocal response. In this review, the different strategies to prevent infection are reported onto titanium and titanium alloy surfaces such as surface modification by antibiotics, antimicrobial peptides, inorganic antibacterial metal elements and antibacterial polymers.
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Selective laser melting (SLM) has enabled the production of porous titanium structures with biological and mechanical properties that mimic bone for orthopedic applications. These ...porous structures have a reduced effective stiffness which leads to improved mechanotransduction between the implant and bone. Triply periodic minimal surfaces (TMPS), specifically the sheet-based gyroid structures, have improved compressive fatigue resistance due lack of stress concentrations. Sheet-based gyroid microarchitectures also have high surface area, permeability, and zero mean curvature. This study examines the effects of the gyroid microarchitectural design in parallel with SLM parameters on structure and function of as-built titanium alloy (Ti6Al4V ELI) scaffolds. Scaffold design was varied by varying unit cell size and wall thickness to produce scaffolds with porosity within the range of trabecular bone (50–90%). Manufacturer’s default and refined laser parameters were used to examine the effect of input energy density on mechanical properties. Scaffolds exhibited a stretching-dominated deformation behavior under both compressive and tensile loading, and porosity dependent stiffness and strength. Internal void defects were observed within the walls of the gyroids structure, serving as sites for crack initiation leading to failure. Refinement of laser parameters resulted in increased compressive and tensile fatigue behavior, particularly for thicker walled gyroid microarchitectures, while thinner walls showed no significant change. The observed properties of as-built gyroid sheet microarchitectures indicates that these structures have potential for use in bone engineering applications. Furthermore, these results highlight the importance of parallel design and processing optimization for complex sheet-based porous structures produced via SLM.
Selective laser melting (SLM) is an additive manufacturing technology which produces complex porous scaffolds for orthopedic applications. Titanium alloy scaffolds with novel sheet-based gyroid microarchitectures were produced via SLM and evaluated for mechanical performance including fatigue behavior. Gyroid structures are function based topologies have been hypothesized to be promising for tissue engineering scaffolds due to the high surface area to volume ratio, zero mean curvature, and high permeability. This paper presents the effects of scaffold design and processing parameters in parallel, a novel study in the field on bone tissue scaffolds produced via additive manufacturing. Additionally, the comparison of compressive and tensile behavior of scaffolds presented is important in characterizing behavior and failure mechanisms of porous metals which undergo complex loading in orthopedic applications.
Interfaces in heterostructures have been a key point of interest in condensed-matter physics for decades owing to a plethora of distinctive phenomena-such as rectification
, the photovoltaic effect
, ...the quantum Hall effect
and high-temperature superconductivity
-and their critical roles in present-day technical devices. However, the symmetry modulation at interfaces and the resultant effects have been largely overlooked. Here we show that a built-in electric field that originates from band bending at heterostructure interfaces induces polar symmetry therein that results in emergent functionalities, including piezoelectricity and pyroelectricity, even though the component materials are centrosymmetric. We study classic interfaces-namely, Schottky junctions-formed by noble metal and centrosymmetric semiconductors, including niobium-doped strontium titanium oxide crystals, niobium-doped titanium dioxide crystals, niobium-doped barium strontium titanium oxide ceramics, and silicon. The built-in electric field in the depletion region induces polar structures in the semiconductors and generates substantial piezoelectric and pyroelectric effects. In particular, the pyroelectric coefficient and figure of merit of the interface are over one order of magnitude larger than those of conventional bulk polar materials. Our study enriches the functionalities of heterostructure interfaces, offering a distinctive approach to realizing energy transduction beyond the conventional limitation imposed by intrinsic symmetry.
Because of the limited penetration depth of visible light that generally excites most of the available photosensitizers (PSs), conventional photodynamic therapy (PDT) is limited to the treatment of ...superficial and flat lesions. Recently, the application of deep penetrating near-infrared (NIR) light excitable upconversion nanoparticles (UCNs) in conjunction with PDT has shown to have clear potential in the treatment of solid tumors due to its ability to penetrate thick tissue. However, various constructs developed so far have certain limitations such as poor or unstable PS loading, reducing their therapeutic efficacy and limiting their application to solution or cell-based studies. In this work, we present a method to fabricate uniform core–shell structured nanoconstruct with a thin layer of photocatalyst or PS–titanium dioxide (TiO2) stably coated on individual UCN core. Our design allows controllable and highly reproducible PS loading, preventing any leakage of PS compared to previously developed nanoconstructs, thus ensuring repeatable PDT results. Further surface modification of the developed nanoconstructs with polyethylene glycol (PEG) rendered them biocompatible, demonstrating good therapeutic efficacy both in vitro and in vivo.
Orthorhombic (space group Pmmm) and tetragonal (space group P422) models are proposed for the Ti.sub.5O.sub.5 (MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII) family of nonstoichiometric titanium ...monoxide Ti.sub.xO.sub.z with double imperfection. The disorder-order (Ti.sub.xO.sub.z (space group Fm bar.3 m)-Ti.sub.5O.sub.5 (space group (Fm bar.3 m)- and Ti.sub.xO.sub.z (space group (Fm bar.3 m)- Ti.sub.5O.sub.5 (space group P422)) transition channels include five superstructure vectors, which belong to stars {k.sub.10}, {k.sub.4(1)}, and {k.sub.4(2)} or {k.sub.10}, {k.sub.6(1)}, and {k.sub.6(2)}, respectively. The functions of distribution of Ti and O atoms over the sites of the model Ti.sub.5O.sub.5 superstructures are calculated. The well-known cubic and monoclinic Ti.sub.5O.sub.5 superstructures are compared with the model orthorhombic and tetragonal superstructures. It is shown that, as temperature decreases, two physically allowable transformation sequences related to the Ti.sub.5O.sub.5 superstructure formation are possible in nonstoichiometric titanium monoxide Ti.sub.xO.sub.z.
Variety of implant materials have been employed in various disciplines of medical science depending on the requirement of a particular application. Metals, alloys, ceramics, and polymers are the ...commonly used biomaterials. The main focus of this study is to review the various structural and microstructural properties of titanium and titanium based alloys used as orthopaedic implants. Orthopaedic implants need to possess certain important qualities to ensure their safe and effective use. These properties like the biocompatibility, relevant mechanical properties, high corrosion and wear resistance and osseointegration are summarized in this review. Various attempts to improve upon these properties like different processing routes, surface modifications have also been inculcated in the paper to provide an insight into the extent of research and effort that has been put into developing a highly superior titanium orthopaedic implant.
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•Process parameters and microstructure are important for selection of implants.•Surface modifications improve biocompatibility, wear, and corrosion resistance.•Equal channel angular pressing improves mechanical properties of titanium implants.•Nano-scale surface features help avoid infection and enhance osseointegration.•Modulus of gyroid scaffold from selective laser melting close to trabecular bone
Powder-based additive manufacturing technologies such as selective laser melting (SLM) and selective electron beam melting (SEBM) hold great promise for producing high-value metal components with ...customized geometries. Development of scanning strategies and prediction of optimal process parameters thereby remain key factors for the fabrication of high-quality products without local inhomogeneities in alloy composition or porosity.
In this contribution, the relation between energy input, evaporation and residual porosity is numerically investigated on the titanium aluminide alloy Ti-48Al-2Cr-2Nb. The numerical model is based on a lattice Boltzmann method and includes hydrodynamics, thermodynamics and multi-component evaporation. Simulation results show that the spatial distribution of alloying elements within the final part is dominated by the advection of melt which is driven by surface tension and evaporative recoil and influenced by the random arrangement of powder particles. Regarding evaporation losses, the line energy appears to be of central importance, as it strongly affects peak temperatures during processing. For a given melt strategy there is a trade-off between porosity and loss of aluminum due to evaporation. It is demonstrated that significant reductions in evaporation losses can be achieved by application of a suitable beam scanning strategy. The presented numerical findings are consistent with experimental data.
As an exoplanet transits its host star, some of the light from the star is absorbed by the atoms and molecules in the planet's atmosphere, causing the planet to seem bigger; plotting the planet's ...observed size as a function of the wavelength of the light produces a transmission spectrum. Measuring the tiny variations in the transmission spectrum, together with atmospheric modelling, then gives clues to the properties of the exoplanet's atmosphere. Chemical species composed of light elements-such as hydrogen, oxygen, carbon, sodium and potassium-have in this way been detected in the atmospheres of several hot giant exoplanets, but molecules composed of heavier elements have thus far proved elusive. Nonetheless, it has been predicted that metal oxides such as titanium oxide (TiO) and vanadium oxide occur in the observable regions of the very hottest exoplanetary atmospheres, causing thermal inversions on the dayside. Here we report the detection of TiO in the atmosphere of the hot-Jupiter planet WASP-19b. Our combined spectrum, with its wide spectral coverage, reveals the presence of TiO (to a confidence level of 7.7σ), a strongly scattering haze (7.4σ) and sodium (3.4σ), and confirms the presence of water (7.9σ) in the atmosphere.
Category:
Hindfoot, Midfoot/Forefoot
Introduction/Purpose:
Lateral column lengthening and a medial cuneiform plantarflexion (Cotton) osteotomy are procedures commonly used in the treatment of ...symptomatic flexible pes planovalgus. Traditionally, structural autograft or allograft have been used for both osteotomies. While union rates for both types of graft have been shown to be comparably high, the use of allograft or autograft each come with their own set of inherent risks and/or potential complications. A trabecular titanium wedge implant provides an attractive alternative that avoids the concerns associated with autograft and allograft use, and has previously been shown in the literature to demonstrate similar union rates. The purpose of this study was to retrospectively review the radiographic outcomes of corrective osteotomies utilizing trabecular metal wedges to address severe flexible pes planovalgus deformity.
Methods:
115 feet in 109 patients who were treated with corrective osteotomies using a trabecular titanium wedges performed by one surgeon were retrospectively reviewed. All patients had symptomatic flexible pes planovalgus, mostly secondary to stage IIB posterior tibialis tendon dysfunction. Other diagnoses included pes planovalgus secondary to the adolescent idiopathic flexible subtype, traumatic posterior tibialis tendon rupture, coalition, or an accessory navicular. Preoperative radiographic parameters assessing severity of deformity were recorded and compared to the postoperative measurements taken at the time of most recent follow up visit to assess for correction. The radiographic measurements included the (1) AP talo-1st metatarsal angle (2) Lateral talo-1st metatarsal angle (3) Calcaneal pitch (4) Lateral talo-calcaneal angle and (5) Talonavicular uncoverage angle. All angles were measured off standard weight-bearing radiographs by one author using our institution’s picture archiving and communication system (PACS) software. All complications were also recorded.
Results:
At an average follow up time of 40 weeks, there were statistically significant corrective changes in the AP-talo-1st metatarsal angle (-12.56), lateral talo-1st metatarsal angle (+14.15), calcaneal pitch (+5.23), lateral talo-calcaneal angle (-3.87) and talonavicular uncoverage angle (-17.76). There were 3 nonunions (2.6%) confirmed by CT, 2 of which were eventually revised. There were a total of 9 complications (7.8%). Other than the nonunion revisions, none of these complications required a return to the operating room. There were no cases of collapse or loss of correction at the time of followup, as compared to the initial post-operative radiographs.
Conclusion:
In our study population corrective osteotomies using a trabecular titanium wedge was effective in improving radiographic parameters associated with flexible pes planovalgus deformity. The nonunion and overall complication rates using a trabecular titanium wedge were shown to be comparable or superior to what has previously been reported in the literature using allograft or autograft.
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![Family of [Ti.sub.5][O.sub....](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/1063-7761/small "Family of [Ti.sub.5][O.sub.5] superstructures")
