In vitro genotoxic effects of titanium dioxide nanoparticles (n‐TiO2) in human sperm cells

Titanium dioxide nanoparticles (TiO₂‐NPs) are one of the most widely engineered nanoparticles used. The study has been focused on TiO ₂‐NPs genotoxic effects on human spermatozoa in vitro. TiO ₂‐NPs are able to cross the blood–testis barrier induced inflammation, cytotoxicity, and gene expression changes that lead to impairment of the male reproductive system. This study presents new data about DNA damage in human sperms exposed in vitro to two n‐TiO ₂ concentrations (1 µg/L and 10 µg/L) for different times and the putative role of reactive oxygen species (ROS) as mediators of n‐TiO ₂ genotoxicity. Primary n‐TiO ₂ characterization was performed by transmission electron microscopy. The dispersed state of the n‐TiO ₂ in media was spectrophotometrically determined at 0, 24, 48, and 72 hr from the initial exposure. The genotoxicity has been highlighted by different experimental approaches (comet assay, terminal deoxynucleotidyl transferase dUTP nick end labeling [TUNEL] test, DCF assay, random amplification of polymorphic DNA polymerase chain reaction [RAPD‐PCR]). The comet assay showed a statistically significant loss of sperm DNA integrity after 30 min of exposure. Increased threshold of sperm DNA fragmentation was highlighted after 30 min of exposure by the TUNEL Test. Also, the RAPD‐PCR analysis showed a variation in the polymorphic profiles of the sperm DNA exposed to n‐TiO ₂. The evidence from the DCF assay showed a statistically significant increase in intracellular ROS linked to n‐TiO ₂ exposure. This research provides the evaluation of n‐TiO ₂ potential genotoxicity on human sperm that probably occurs through the production of intracellular ROS.     

The Effect of Hole Transport Material Pore Filling on Photovoltaic Performance in Solid‐State Dye‐Sensitized Solar Cells

A detailed investigation of the effect of hole transport material (HTM) pore filling on the photovoltaic performance of solid‐state dye‐sensitized solar cells (ss‐DSCs) and the specific mechanisms involved is reported. It is demonstrated that the efficiency and photovoltaic characteristics of ss‐DSCs improve with the pore filling fraction (PFF) of the HTM, 2,2’,7,7’‐tetrakis‐(N, N ‐di‐ p ‐methoxyphenylamine)9,9’‐spirobifluorene(spiro‐OMeTAD). The mechanisms through which the improvement of photovoltaic characteristics takes place were studied with transient absorption spectroscopy and transient photovoltage/photocurrent measurements. It is shown that as the spiro‐OMeTAD PFF is increased from 26% to 65%, there is a higher hole injection efficiency from dye cations to spiro‐OMeTAD because more dye molecules are covered with spiro‐OMeTAD, an order‐of‐magnitude slower recombination rate because holes can diffuse further away from the dye/HTM interface, and a 50% higher ambipolar diffusion coefficient due to an improved percolation network. Device simulations predict that if 100% PFF could be achieved for thicker devices, the efficiency of ss‐DSCs using a conventional ruthenium‐dye would increase by 25% beyond its current value.     

Evaluation of the mechanical properties and clinical application of nickel–titanium shape memory alloy scaphoid arc nail

To investigate the mechanical and biomechanical properties of nickel–titanium (Ni–Ti) shape memory alloy scaphoid arc nail (NT‐SAN) fixator as well as study the surgical method of treating carpal scaphoid fractures and evaluate its clinical efficacy. (1) Static and dynamic bending tests with embedded axial bending fixture were conducted to study the mechanical properties. (2) To evaluate biomechanical strength and fatigue, 32 scaphoid samples were classified into four groups to perform the fixation rigidity test: intramedullary Kirschner fixation (group A), Kirschner straddle nail fixation (group B), screw nail fixation (group C), and NT‐SAN fixation (group D). Next, 24 scaphoid waist fracture models were classified to conduct fatigue experiments as follows: Kirschner straddle nail fixation (group E), screw nail fixation (group F), and NT‐SAN fixation (group G). (3) The Krimmer score chart was used for clinical evaluations. (1) NT‐SAN showed excellent mechanical performance and a long lifespan. (2) NT‐SAN was fixated with a strong intensity and an anti‐fatigue outcome. (3) Ninety‐eight interviewed patients were satisfied with the therapeutic effects of the arc nail (satisfaction rate: 95.92%). The designed strength and hardness of NT‐SAN corresponded with the anatomical characteristics of the scaphoid, and the designed mechanical properties met the biomechanical requirements of a scaphoid fracture. The fatigue strength can meet the requirements of bone healing after the scaphoid fracture. Clinical trials on NT‐SAN scaphoid fracture treatment have shown that the surgery is simple and the clinical results are satisfactory. The therapeutic level of NT‐SAN is III; thus, it is worth promoting.     

Sequential Blade‐Coated Acceptor and Donor Enables Simultaneous Enhancement of Efficiency,Stability, and Mechanical Properties for Organic Solar Cells

As a predominant fabrication method of organic solar cells (OSCs), casting of a bulk heterojunction (BHJ) structure presents overwhelming advantages for achieving higher power conversion efficiency (PCE). However, long‐term stability and mechanical strength are significantly crucial to realize large‐area and flexible devices. Here, controlling blend film morphology is considered as an effective way toward co‐optimizing device performance, stability, and mechanical properties. A PCE of 12.27% for a P‐i‐N‐structured OSC processed by sequential blade casting (SBC) is reported. The device not only outperforms the as‐cast BHJ devices (11.01%), but also shows impressive stability and mechanical properties. The authors corroborate such enhancements with improved vertical phase separation and purer phases toward more efficient transport and collection of charges. Moreover, adaptation of SBC strategy here will result in thermodynamically favorable nanostructures toward more stable film morphology, and thus improving the stability and mechanical properties of the devices. Such co‐optimization of OSCs will pave ways toward realizing the highly efficient, large‐area, flexible devices for future endeavors.     

High‐Energy,High‐Rate,Lithium–Sulfur Batteries: Synergetic Effect of Hollow TiO2‐Webbed Carbon Nanotubes and a Dual Functional Carbon‐Paper Interlayer

A novel nanocomposite cathode consisting of sulfur and hollow‐mesoporous titania (HMT) embedded within carbon nanotubes (CNT), which is designated as S‐HMT@CNT, has been obtained by encapsulating elemental sulfur into the pores of hollow‐mesoporous, spherical TiO₂ particles that are connected via CNT. A carbon‐paper interlayer, referred to as dual functional porous carbon wall (DF‐PCW), has been obtained by filling the voids in TiO₂ spheres with carbon and then etching the TiO₂ template with a chemical process. The DF‐PCW interlayer provides a medium for scavenging the lithium polysulfides and suppressing them from diffusing to the anode side when it is inserted between the sulfur cathode and the separator. Lithium–sulfur cells fabricated with the thus prepared S‐HMT@CNT cathode and the DF‐PCW interlayer exhibit superior performance due to the containment of sulfur in TiO₂ and improved lithium–ion and electron transports. The Li–S cells display high capacity with excellent capacity retention at rates as high as 1C, 2C, and 5C rates.     

Changes in nano‐mechanical properties of human epidermal cornified cells depending on their proximity to the skin surface

During formation of the stratum corneum (SC) barrier, terminally differentiated keratinocytes continue their maturation process within the dead superficial epidermal layer. Morphological studies of isolated human corneocytes have revealed differences between cornified envelopes purified from the deep and superficial SC. We used atomic force microscopy to measure the mechanical properties of native human corneocytes harvested by tape‐stripping from different SC depths. Various conditions of data acquisition have been tested and optimized, in order to obtain exploitable and reproducible results. Probing at 200 nN allowed us to investigate the total stiffness of the cells (at 50 nm indentation) and that of the cornified envelopes (at 10 to15 nm), and lipid envelopes (at 5 to 10 nm). The obtained data indicated statistically significant differences between the superficial (more rigid) and deep (softer) corneocytes, thus confirming the existence of depth and maturation‐related morphological changes within the SC. The proposed approach can be potentially used for minimally invasive evaluation of various skin conditions such as aging, skin hydration, and pathologies linked to SC.     

Biosilica‐loaded poly(ϵ‐caprolactone) nanofibers mats provide a morphogenetically active surface scaffold for the growth and mineralization of the osteoclast‐related SaOS‐2 cells

Bioprinting/3D cell printing procedures for the preparation of scaffolds/implants have the potential to revolutionize regenerative medicine. Besides biocompatibility and biodegradability, the hardness of the scaffold material is of critical importance to allow sufficient mechanical protection and, to the same extent, allow migration, cell–cell, and cell–substrate contact formation of the matrix‐embedded cells. In the present study, we present a strategy to encase a bioprinted, cell‐containing, and soft scaffold with an electrospun mat. The electrospun poly(?‐caprolactone) (PCL) nanofibers mats, containing tetraethyl orthosilicate (TEOS), were subsequently incubated with silicatein. Silicatein synthesizes polymeric biosilica by polycondensation of ortho‐silicate that is formed from prehydrolyzed TEOS. Biosilica provides a morphogenetically active matrix for the growth and mineralization of osteoblast‐related SaOS‐2 cells in vitro. Analysis of the microstructure of the 300–700 nm thick PCL/TEOS nanofibers, incubated with silicatein and prehydrolyzed TEOS, displayed biosilica deposits on the mats formed by the nanofibers. We conclude and propose that electrospun PCL nanofibers mats, coated with biosilica, may represent a morphogenetically active and protective cover for bioprinted cell/tissue‐like units with a suitable mechanical stability, even if the cells are embedded in a softer matrix.     

Effect of scaffold material, construct length and mechanical stimulation on the in vitro stiffness of the engineered tendon construct

Introducing mesenchymal stem cell (MSC)-seeded collagen constructs into load-protected wound sites in the rabbit patellar and Achilles tendons significantly improves their repair outcome compared to natural healing of the unfilled defect. However, these constructs would not be acceptable alternatives for repairing complete tendon ruptures because they lack the initial stiffness at the time of surgery to resist the expected peak in vivo forces thereafter. Since the stiffness of these constructs has also been shown to positively correlate with the stiffness of the subsequent repairs, improving initial stiffness by appropriate selection of in vitro culture conditions would seem crucial. In this study we examined the individual and combined effects of collagen scaffold type, construct length, and mechanical stimulation on in vitro implant stiffness. Two levels each of scaffold material (collagen gel vs. collagen sponge), construct length (short vs. long), and mechanical stimulation (stimulated vs. non-stimulated) were examined. Our results indicate that all three treatment factors influenced construct linear stiffness. Increasing the length of the construct had the greatest effect on the stiffness compared to introducing mechanical stimulation or changing the scaffold material. A significant interaction was also found between length and stimulation. Of the eight groups studied, longer, stimulated, cell-sponge constructs showed the highest in vitro linear stiffness. We now plan in vivo studies to determine if higher stiffness constructs generate higher stiffness repairs 12 weeks after surgery and if in vitro construct stiffness continues to correlate with in vivo repair parameters like linear stiffness.     

Effect of carbopol and polyvinylpyrrolidone on the mechanical, rheological, and release properties of bioadhesive polyethylene glycol gels

This study examined the mechanical (hardness, compressibility, adhesiveness, and cohesiveness) and rheological (zero-rate viscosity and thixotropy) properties of polyethylene glycol (PEG) gels that contain different ratios of Carbopol 934P (CP) and polyvinylpyrrolidone K90 (PVP). Mechanical properties were examined using a texture analyzer (TA-XT2), and rheological properties were examined using a rheometer (Rheomat 115A). In addition, lidocaine release from gels was evaluated using a release apparatus simulating the buccal condition. The results indicated that an increase in CP concentration significantly increased gel compressibility, hardness, and adhesiveness, factors that affect ease of gel removal from container, ease of gel application onto mucosal membrane, and gel bioadhesion. However, CP concentration was negatively correlated with gel cohesiveness, a factor representing structural reformation. In contrast, PVP concentration as negatively correlated with gel hardness and compressibility, but positively correlated with gel cohesiveness. All PEG gels exhibited pseudoplastic flow with thixotropy, indicating a general loss of consistency with increased shearing stress. Drug release T_50% was affected by the flow rate of the simulated saliva solution. A reduction in the flow rate caused a slower drug release and hence a higher T_50% value. In addition, drug release was significantly reduced as the concentrations of CP and PVP increased because of the increase in zero-rate viscosity of the gels. Response surfaces and contour plots of the dependent variables further substantiated that various combinations of CP and PVP in the PEG gels offered a wide range of mechanical, rheological, and drug-release characteristics. A combination of CP and PVP with complementary physical properties resulted in a prolonged buccal drug delivery.     

Effect of a single impact loading on the structure and mechanical properties of articular cartilage

AIM: To study the effect of a single impact on the structure and mechanical properties of cartilage. MATERIALS AND METHOD: Osteochondral plugs harvested from bovine femora were subjected each to a single impact using an in-house designed drop-tower. Impact masses of different values were released from different drop heights in selected combinations to apply stresses at strain rates and impact energies within specific ranges. Changes in the storage and loss moduli were estimated from cyclic compressive loading test undertaken before and after impact. The conditions of these tests were set to those occurring during walking and running. The extent of the damage on cartilage surface and depth was assessed using optical and confocal microscopy. RESULTS: The storage modulus varied slightly at level walking and running after performing impact tests up to the impact energy of 0.736 J. However, the decrease in the storage modulus was considerable at the impact energy of 1.962 J for test conditions representing both walking and running. This impact energy resulted in strain rate of 1500 s(-1), stress of 25 MPa and energy absorbed per unit volume of 12.79 mJ/mm(3). After impact the loss modulus increased over the loading cycles at all energies. Severe fissures were observed across the cartilage surface and through its thickness at levels of impact energy equal or greater than 1.472 J. CONCLUSIONS: This study identified thresholds for the strain rate, impact stress and impact energy, which caused permanent changes in the mechanical properties and damage to structure of cartilage.     

Size,but not sex,predicts pinch force and exoskeleton mechanical properties in crayfish of the genus Faxonius

Studies of animal weaponry and defensive structures rarely take into consideration their underlying mechanical properties. We measured the compressive strength and thickness of the exoskeleton of the claw (chela) in two North American crayfish species, Faxonius virilis and F. limosus. We performed similar measures on the carapace, a body region not directly involved in agonistic contests. Males of both species generated significantly stronger maximum pinch forces than females. However, these differences can be attributed to differences in claw size between the sexes. The thickness (ultrastructure) of the claw exoskeleton was a significant predictor of its compressive strength and likely explained the difference in compressive strength we observed between the two species. Neither claw thickness nor claw compressive strength was correlated with maximum pinch force. Additionally, we found that crayfish body size was a strong predictor of carapace compressive strength and thickness, whereas sex was not. The claw had greater compressive strength and thickness than the corresponding values for the carapace. Our study shows that the mechanical properties of the crayfish exoskeleton are largely a function of size and highlights the need to integrate mechanical properties into studies of animal morphology and performance.     

Functionalization of poly(amidoamine) dendrimer‐based nano‐architectures using a naphthalimide derivative and their fluorescent,dyeing and antimicrobial properties on wool fibers

Novel naphthalimide–poly(amidoamine) dendrimer fluorescent dyes were synthesized, and their structures were identified and confirmed using different characterization methods such as Fourier transform infrared, ¹H NMR, ¹³C NMR, differential scanning calorimetry, elemental analysis and UV–vis spectroscopy. The spectrophotometric studies demonstrated absorption maxima (λ_max) and extinction coefficient (ε_max) values in the ranges of 429–438 nm and 25,635–88,618 L/mol/cm, respectively. The dyeing, fastness and antimicrobial properties of dyed wool fibers were examined. Colorimetric measurements demonstrated a greenish‐yellow hue with remarkable fluorescence intensity on dyed wool. Although the fastness properties of naphthalimide dye on wool fibers were poor/moderate, color fastness was appreciably improved through modification of the dye using dendrimers. The results revealed that the newly synthesized dyes are potent antimicrobial agents on wool fibers. Overall, it was deduced that poly(amidoamine) (PAMAM) dendrimers could be exploited as a promising tool in tailoring the different properties of naphthalimide dyes, being suitable for dyeing and antimicrobial finishing agents for wool fibers. Copyright © 2015 John Wiley & Sons, Ltd.     

Effects of mechanical vibration on cell morphology,proliferation, apoptosis,and cytokine expression/secretion in osteocyte‐like MLO‐Y4 cells exposed to high glucose

Diabetic patients exhibit significant bone deterioration. Our recent findings demonstrate that mechanical vibration is capable of resisting diabetic bone loss, whereas the relevant mechanism remains unclear. We herein examined the effects of mechanical vibration on the activities and functions of osteocytes (the most abundant and well‐recognized mechanosensitive cells in the bone) exposed to high glucose (HG). The osteocytic MLO‐Y4 cells were incubated with 50 mM HG for 24 h, and then stimulated with 1 h/day mechanical vibration (0.5 g, 45 Hz) for 3 days. We found that mechanical vibration significantly increased the proliferation and viability of MLO‐Y4 cells under the HG environment via the MTT, BrdU, and Cell Viability Analyzer assays. The apoptosis detection showed that HG‐induced apoptosis in MLO‐Y4 cells was inhibited by mechanical vibration. Moreover, increased cellular area, microfilament density, and anisotropy in HG‐incubated MLO‐Y4 cells were observed after mechanical vibration via the F‐actin fluorescence staining. The real‐time polymerase chain reaction and western blotting results demonstrated that mechanical vibration significantly upregulated the gene and protein expression of Wnt3a, β‐catenin, and osteoprotegerin (OPG) and decreased the sclerostin, DKK1, and receptor activator for nuclear factor‐κB ligand (RANKL) expression in osteocytes exposed to HG. The enzyme‐linked immunosorbent assay assays showed that mechanical vibration promoted the secretion of prostaglandin E₂ and OPG, and inhibited the secretion of tumor necrosis factor‐α and RANKL in the supernatant of HG‐treated MLO‐Y4 cells. Together, this study demonstrates that mechanical vibration improves osteocytic architecture and viability, and regulates cytokine expression and secretion in the HG environment, and implies the potential great contribution of the modulation of osteocytic activities in resisting diabetic osteopenia/osteoporosis by mechanical vibration.     

Effects of Daphnia ‐Associated Infochemicals on the Morphology,Polysaccharides Content and PSII‐Efficiency in Scenedesmus obliquus

We investigated the effects of infochemicals from Daphnia carinata on the morphology, polysaccharides yield and PSII‐efficiency in Scenedesmus obliquus. Infochemicals released from D. carinata induced colony formation in S. obliquus. The contents of soluble extracellular polysaccharides, bounded extracellular polysaccharides, and the total polysaccharides per cell in the induced colonies of S. obliquus increased significantly relative to those of the unicells, which indicated that Daphnia ‐associated infochemicals could also stimulate S. obliquus to increase the synthesis of extracellular polysaccharides. The increased extracellular polysaccharides may play an important role in cementing S. obliquus cells together to form colonies. In addition, no significant differences in growth, the maximal efficiency of PSII photochemistry (F_v/F_m), and the effective quantum yields of PSII (Φ_PSII) were detected between unicellular and induced colonial populations, which showed that the cost of induced colony formation was not reflected on these indices. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The role of chromium and nickel on the thermal and mechanical properties of FeNiCr austenitic stainless steels under high pressure and temperature: a molecular dynamics study

The effect of Cr and Ni content on thermo-mechanical properties of FeNiCr austenitic stainless steel under ambient and high pressure and temperature were investigated by MD simulations. The FCC structure was selected as optimum structure for FeNiCr system based on obtained MD results from Bonny EAM potential and valid experimental results. The structural and mechanical properties of pure Fe, Ni, and Cr were also estimated based on this potential, indicating good agreement with experimental results. These properties were computed for four experimental case studies which showed less than 10% error. Moreover, the elastic constants of the Fe–(8–18)Ni–(18–25)Cr systems were estimated. Results showed that bulk modulus increases by increasing the Ni and Cr contents, which can be connected to the changes in bonding electrons. The thermal properties of FeNiCr were calculated in ambient and high pressure. Although thermo-mechanical properties confirm good agreement with experimental results at the ambient condition, however, they indicate that FeNiCr Bonny potential is not applicable at high pressure. In order to tackle this issue, a hybrid potential was used at high Pressure/Temperature. The results illustrate enhanced mechanical properties, increase of melting point and reduction of LTE in high pressure and deteriorated mechanical properties at high temperature.     

Doping‐Induced Screening of the Built‐in‐Field in Organic Solar Cells: Effect on Charge Transport and Recombination

We report on the effects of screening of the electric field by doping‐induced mobile charges on photocurrent collection in operational organic solar cells. Charge transport and recombination were studied using double injection (DI) and charge extraction by linearly increasing voltage (CELIV) transient techniques in bulk‐heterojunction solar cells made from acceptor‐donor blends of poly(3‐n‐hexylthiophene):phenyl‐C61‐butyric acid methyl ester (P3HT:PC60BM). It is shown that the screening of the built‐in field in operational solar cells can be controlled by an external voltage while the influence on charge transport and recombination is measured. An analytical theory to extract the bimolecular recombination coefficient as a function of electric field from the injection current is also reported. The results demonstrate that the suppressed (non‐Langevin) bimolecular recombination rate and charge collection are not strongly affected by native doping levels in this materials combination. Hence, it is not necessary to reduce the level of doping further to improve the device performance of P3HT‐based solar cells.