Peripheral nerve injuries (PNIs) are the most common injury types to affect the nervous system. Restoration of nerve function after PNI is a challenging medical issue. Extended gaps in transected ...peripheral nerves are only repaired using autologous nerve grafting. This technique, however, in which nerve tissue is harvested from a donor site and grafted onto a recipient site in the same body, has many limitations and disadvantages. Recent studies have revealed artificial nerve conduits as a promising alternative technique to substitute autologous nerves. This Review summarizes different types of artificial nerve grafts used to repair peripheral nerve injuries. These include synthetic and natural polymers with biological factors. Then, desirable properties of nerve guides are discussed based on their functionality and effectiveness. In the final part of this Review, fabrication methods and commercially available nerve guides are described.
This paper describes the improvements in microwave absorbency and other functional properties of silicone rubber-based nanocomposite sheets with iron (Fe)- and nickel (Ni)-deposited nanographite ...(NG). NG was synthesized using the ball milling method and then acid functionalized. The deposition was performed on acid-functionalized NG dispersed in an electrochemical bath containing Fe and Ni salts in a designed fluidized bed reactor system. The electrolyte concentration, stirring speed, applied current, and time of electrolysis were optimized. X-ray diffraction, Fourier transform infrared spectroscopy, Brenner–Emmet–Teller analysis, transmission electron microscopy, scanning electron microscopy, and atomic force microscopy were used to characterize the structural as well as morphological properties of the material. The applied current, average particle size, and density of the electrolyte–powder suspension have a significant impact on the material’s morphology and microwave absorption capabilities. To measure tensile strength, electrical impedance, and microwave absorption in the 2–20 GHz range, co-deposited nanographite was mixed in a silicone rubber matrix and molded into 1.00–2.00 mm thick nanocomposite sheets. The nanocomposite sheets demonstrated a − 15 dB reflection loss in the 9–13 GHz frequency band with an absorber thickness of 1.24 mm.
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Application of hydrostatic pressure under adiabatic conditions causes a change in temperature in any substance. This effect is known as the barocaloric effect and the vast majority of materials heat ...up when adiabatically squeezed, and they cool down when pressure is released (conventional barocaloric effect). There are, however, materials exhibiting an inverse barocaloric effect: they cool when pressure is applied, and they warm when it is released. Materials exhibiting the inverse barocaloric effect are rather uncommon. Here we report an inverse barocaloric effect in the intermetallic compound La-Fe-Co-Si, which is one of the most promising candidates for magnetic refrigeration through its giant magnetocaloric effect. We have found that application of a pressure of only 1 kbar causes a temperature change of about 1.5 K. This value is larger than the magnetocaloric effect in this compound for magnetic fields that are available with permanent magnets.
Three-dimensional bioprinting is a promising technology for bone tissue engineering. However, most hydrogel bioinks lack the mechanical and post-printing fidelity properties suitable for such hard ...tissue regeneration. To overcome these weak properties, calcium phosphates can be employed in a bioink to compensate for the lack of certain characteristics. Further, the extracellular matrix of natural bone contains this mineral, resulting in its structural robustness. Thus, calcium phosphates are necessary components of bioink for bone tissue engineering. This review paper examines different recently explored calcium phosphates, as a component of potential bioinks, for the biological, mechanical and structural properties required of 3D bioprinted scaffolds, exploring their distinctive properties that render them favorable biomaterials for bone tissue engineering. The discussion encompasses recent applications and adaptations of 3D-printed scaffolds built with calcium phosphates, delving into the scientific reasons behind the prevalence of certain types of calcium phosphates over others. Additionally, this paper elucidates their interactions with polymer hydrogels for 3D bioprinting applications. Overall, the current status of calcium phosphate/hydrogel bioinks for 3D bioprinting in bone tissue engineering has been investigated.
Conventional superconductors are robust diamagnets that expel magnetic fields through the Meissner effect. It would therefore be unexpected if a superconducting ground state would support spontaneous ...magnetics fields. Such broken time-reversal symmetry states have been suggested for the high-temperature superconductors, but their identification remains experimentally controversial. We present magnetization, heat capacity, zero field and transverse field muon spin relaxation experiments on the recently discovered caged type superconductor Y5Rh6Sn18 ( TC= 3.0 K). The electronic heat capacity of Y5Rh6Sn18 shows a T(3) dependence below Tc indicating an anisotropic superconducting gap with a point node. This result is in sharp contrast to that observed in the isostructural Lu5Rh6Sn18 which is a strong coupling s-wave superconductor. The temperature dependence of the deduced superfluid in density Y5Rh6Sn18 is consistent with a BCS s-wave gap function, while the zero-field muon spin relaxation measurements strongly evidences unconventional superconductivity through a spontaneous appearance of an internal magnetic field below the superconducting transition temperature, signifying that the superconducting state is categorized by the broken time-reversal symmetry.
Bioglasses are used in applications related to bone rehabilitation and repair. The mechanical and bioactive properties of polysaccharides like alginate and agarose can be modulated or improved using ...bioglass nanoparticles. Further essential metal ions used as crosslinker have the potential to supplement cultured cells for better growth and proliferation.
In this study, the alginate bioink is modulated for fabrication of tissue engineering scaffolds by extrusion-based 3D bioprinting using agarose, bioglass nanoparticles and combination of essential trace elements such as iron, zinc, and copper. Homogeneous bioink was obtained by in situ mixing and bioprinting of its components with twin screw extruder (TSE) based 3D bioprinting, and then distribution of metal ions was induced through post-printing diffusion of metal ions in the printed scaffolds. The mechanical and 3d bioprinting properties, microscopic structure, biocompatibility of the crosslinked alginate/agarose hydrogels were analyzed for different concentrations of bioglass. The adipose derived mesenchymal stem cells (ADMSC) and osteoblast cells (MC3T3) were used to evaluate this hydrogel's biological performances.
The porosity of hydrogels significantly improves with the incorporation of the bioglass. More bioglass concentration results in improved mechanical (compressive, dynamic, and cyclic) and 3D bioprinting properties. Cell growth and extracellular matrix are also enhanced with bioglass concentration.
For bioprinting of the bioinks, the advanced TSE head was attached to 3D bioprinter and in situ fabrication of cell encapsulated scaffold was obtained with optimized composition considering minimal effects on cell damage. Fabricated bioinks demonstrate a biocompatible and noncytotoxic scaffold for culturing MC3T3 and ADMSC, while bioglass controls the cellular behaviors such as cell growth and extracellular matrix formation.
Worldwide, many people suffer from knee injuries and articular cartilage damage every year, which causes pain and reduces productivity, life quality, and daily routines. Medication is currently ...primarily used to relieve symptoms and not to ameliorate cartilage degeneration. As the natural healing capacity of cartilage damage is limited due to a lack of vascularization, common surgical methods are used to repair cartilage tissue, but they cannot prevent massive damage followed by injury.
Functional tissue engineering has recently attracted attention for the repair of cartilage damage using a combination of cells, scaffolds (constructs), biochemical factors, and biomechanical stimuli. As cyclic biomechanical loading is the key factor in maintaining the chondrocyte phenotype, many studies have evaluated the effect of biomechanical stimulation on chondrogenesis. The characteristics of hydrogels, such as their mechanical properties, water content, and cell encapsulation, make them ideal for tissue-engineered scaffolds. Induced cell signaling (biochemical and biomechanical factors) and encapsulation of cells in hydrogels as a construct are discussed for biomechanical stimulation-based tissue regeneration, and several notable studies on the effect of biomechanical stimulation on encapsulated cells within hydrogels are discussed for cartilage regeneration.
Induction of biochemical and biomechanical signaling on the encapsulated cells in hydrogels are important factors for biomechanical stimulation-based cartilage regeneration.
The current study investigates iron (Fe)-nickel (Ni)-nanographite (NG) / silicone rubber composites for improved microwave absorption in 8–18 GHz range. Fe–Ni particles were produced in three ...different ratios (50:50, 60:40, and 75:25) using high-energy planetary ball mill. NG was also prepared from graphite using wet milling. The Fe–Ni combinations were then ball milled with NG at 75:25 ratio (Fe–Ni: NG) and coded as (Fe
0.75
Ni
0.25
)
0.75
NG
0.25
, (Fe
0.6
Ni
0.4
)
0.75
NG
0.25
, and (Fe
0.5
Ni
0.5
)
0.75
NG
0.25
. These hybrid nanoparticles were investigated for their structural and morphological properties. The thermomechanical, environmental and electromagnetic properties of silicone rubber composites with these nanoparticles (20% w/w) were studied. Around 60% improvement in tensile strength with 40% more elongation is achieved compared to the pure silicone rubber samples. (Fe
0.5
Ni
0.5
)
0.75
NG
0.25
based sample shows good dynamic mechanical properties with almost 4 times increase in storage modulus and twice increase in loss modulus from − 20 °C to room temperature. The conducting nature of hybrid nanoparticles helps to reduce the electrical impedance up to two orders (from 10
4
to 10
2
Ω). The composites with (Fe
0.75
Ni
0.25
)
0.75
NG
0.25
have excellent mechanical characteristics and good dielectric and magnetic loss while the electromagnetic characteristics of (Fe
0.6
Ni
0.4
)
0.75
NG
0.25
based composites have shown greater broad-spectrum absorption in 8–18 GHz range. Real and imaginary permittivity values are up to 50 and 8, respectively while real and imaginary permeability values are around 1 and 0.5, respectively. The results indicate that these flexible polymer nanocomposite sheets are a viable contender as microwave absorbers in a variety of stealth applications over wide range environmental conditions.
The Development of bioresponsive extrudable hydrogels for 3D bioprinting is imperative to address the growing demand for scaffold design as well as efficient and reliable methods of tissue ...engineering and regenerative medicine. This study proposed genipin (5 mg) cross-linked gelatin (1 to 1.5 g)-hyaluronic acid (0.3 g) hydrogel bioink (20 mL) tailored for 3D bioprinting. The focus is on high cell loading and a less artificial extra-cellular matrix (ECM) effect, as well as exploring their potential applications in tissue engineering. The bioresponsiveness of these hydrogel scaffolds was successfully evaluated at 37 °C and room temperature (at pH 2.5, 7.4, and 9). The rheological and mechanical properties (more than three times) increased with the increase in gelatin content in the hydrogel; however, the hydrogel with the least amount of gelatin showed the best extrusion capability. This optimized hydrogel’s high extrusion ability and post-printing shape fidelity were evident from 3D and four-axis printing of complex structures such as hollow tubes, stars, pyramids, and zigzag porous tubular (four-axis) scaffolds (printed at 90 kPa pressure, 70 mm/s speed, 22G needle, fourth axis rotation of 4 rpm). 3 million/mL MC3T3-E1 mouse osteoblast cells were used in preparing 3D bioprinted samples. The in vitro cell culture studies have been carried out in a CO2 incubator (at 37 °C, 5% CO2). In the cytocompatibility study, almost three times more cell viability was observed in 3 days compared to day 1 control, proving the non-toxicity and cell-supportiveness of these hydrogels. High cell viability and cell-to-cell interactions observed at the end of day 3 using this moderately stable hydrogel in 3D bioprinting exhibit high potential for precise cell delivery modes in tissue engineering as well as regenerative medicine.
In the present study, we address the combined response of iron (Fe) and nickel (Ni) metal powders on the microwave absorption properties of nanographite (NG) particles in the 8–18 GHz frequency band. ...NG was synthesized from graphite via high-energy planetary ball mill (wet milling). Similarly, hybrid Fe-Ni-NG particles in two individual (25:25:50 and 37.5:37.5:25) ratios were synthesized and characterized for studying their structural and morphological properties. Further, the samples were dispersed in epoxy-based aero-grade paints to analyze their particle size and rheological properties. Thus, produced nanocomposite paints were coated on aluminum sheets for analyzing their functional properties including impedance measurement and microwaves absorbency measurements. The hybrid nanoparticle coatings exhibited a reflection loss of − 21 dB for 25:25:50 (Fe-Ni-NG) sample at 18 GHz and nearly − 18 dB for 37.5:37.5:25 (Fe-Ni-NG) sample for a wider frequency range from 14 to 18 GHz with a coating thickness of 1.8 mm. These advanced nanoparticles can be used for the development of flexible coatings in various defense applications including stealth aircrafts and low observable technologies in the future.
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