Poly(dopamine) and Ag nanoparticle-loaded TiO2 nanotubes with optimized antibacterial and ROS-scavenging bioactivities

AIM

To create polydopamine (PDA) and Ag nanoparticle-loaded TiO₂ nanotubes coating on titanium (Ti) alloy.

MATERIALS & METHODS

TiO₂-PDA-Ag coating was fabricated on Ti implants by electrochemical anodization. The in vitro and in vivo bactericidal and antibiofilm activities were tested. Intracellular reactive oxygen species (ROS) and antioxidative capability were measured, and cell proliferation, adhesion and cell morphology were characterized.

RESULTS

TiO₂-PDA-Ag coating showed satisfactory bactericidal and antibiofilm activities in vitro and in vivo, improved Ag release pattern, evident ROS scavenging properties and enhanced cell adhesion and proliferation.

CONCLUSION

Our study successfully fabricated a PDA and Ag nanoparticle-loaded TiO₂ nanotubes coating on Ti alloy. The improved Ag release kinetics and ROS-scavenging properties achieve an optimal balance between antibacterial ability and biocompatibility.

The role of Th1/Th2 cytokines played in regulation of specific CD4 + Th1 cell conversion and activation during inflammatory reaction of chronic obstructive pulmonary disease

CD4 ⁺ Th1-CXCR3 signalling pathway may play a key role in chronic obstructive pulmonary disease (COPD). The aim of this study was to explore Th1/Th2 cytokines ratio differences in patients in different stages of COPD and to confirm the hypothesis that elastin exposure might serve as an antigen to initiate the stimulation of CD4 ⁺ Th1-CXCR3 immune inflammation pathway. Patients of COPD in different stages and normal individuals were enrolled. Ten millilitres of peripheral blood was drawn from patients. The concentration of CXCR3, IFN-γ, IL-2, IL-4 and IL-13 in plasma was detected by ELISA. The Naïve CD4⁺ T cells were isolated from the peripheral blood mononuclear cells, which were stimulated by elastin and collagen before determining the level of IFN-γ secretion by ELISPOT. Compared with control group, the concentration of CXCR3 in the acute exacerbation COPD (AECOPD) group was higher (P < .05). The concentration of IFN-γ and IL-2 in AECOPD group was lower than that in remission (P < .05). The concentration of IFN-γ in the AECOPD and remission was higher than that in controls (P < .05), while IL-2 was opposite (P < .01). The concentration of IL-4 and IL-13 in AECOPD group was higher than that in the controls (P < .05). The CD4⁺ Th1 cells stimulated by the elastin as antigen secreted more IFN-γ than that by collagen (P < .01). CXCR3 was highly expressed in patients with COPD. There were different Th1/Th2 cytokines in different stages of COPD. The CD4+Th1-specific conversion and activation may be an initiator of COPD immune inflammatory response.

In Situ Synthesis of MoP Nanoflakes Intercalated N-Doped Graphene Nanobelts from MoO3 -Amine Hybrid for High-Efficient Hydrogen Evolution Reaction

Molybdenum phosphide (MoP) is a promising non-noble-metal electrocatalyst in the hydrogen evolution reaction (HER), but practical implementation is impeded by the sluggish HER kinetics and poor chemical stability. Herein, a novel high-efficiency HER electrocatalyst comprising MoP nanoflakes intercalated nitrogen-doped graphene nanobelts (MoP/NG), which are synthesized by one-step thermal phosphiding organic-inorganic hybrid dodecylamine (DDA) inserted MoO₃ nanobelts, is reported. The intercalated DDA molecules are in situ carbonized into the NG layer and the sandwiched MoO₃ layer is converted into MoP nanoflakes which are intercalated between the NG layers forming the alternatingly stacked MoP/NG hybrid nanobelts. The MoP nanoflakes provide abundant edge sites and the sandwiched MoP/NG hybrid enables rapid ion/electron transport thus yielding excellent electrochemical activity and stability for HER. The MoP/NG shows a low overpotential of 94 mV at 10 mA cm^-2 , small Tafel slope of 50.1 mV dec^-1 , and excellent electrochemical stability with 99.5% retention for over 22 h.

Hierarchical TiN nanoparticles-assembled nanopillars for flexible supercapacitors with high volumetric capacitance

Titanium nitride (TiN) is an attractive electrode material in fast charging/discharging supercapacitors because of its excellent conductivity. However, the low capacitance and mechanical brittleness of TiN restricts its further application in flexible supercapacitors with high energy density. Thus, it is still a challenge to rationally design TiN electrodes with both high electrochemical and mechanical properties. Herein, the hierarchical TiN nanoparticles-assembled nanopillars (H-TiN NPs) array as binder free electrodes were obtained by nitriding of hierarchical titanium dioxide (TiO2) nanopillars, which was produced by a simple hydrothermal treatment of anodic TiO2 nanotubes (NTs) array in water. The porous TiN nanoparticles connected to each other to form ordered nanopillar arrays, effectively providing larger specific surface area and more active sites for charge storage. The H-TiN NPs delivered a high volumetric capacitance of 120 F cm-3 at 0.83 A cm-3, which is better than that of TiN NTs arrays (69 F cm-3 at 0.83 A cm-3). After assembling into all-solid-state devices, the H-TiN NPs based supercapacitors exhibited outstanding volumetric capacitance of 5.9 F cm-3 at 0.02 A cm-3 and a high energy density of 0.53 mW h cm-3. Our results reveal a new strategy to optimize the supercapacitive performance of metal nitrides.

[Application of 3D virtual reality technology with multi-modality fusion in resection of glioma located in central sulcus region]

Objective: To explore the clinical and teaching application value of virtual reality technology in preoperative planning and intraoperative guide of glioma located in central sulcus region. Method: Ten patients with glioma in the central sulcus region were proposed to surgical treatment. The neuro-imaging data, including CT, CTA, DSA, MRI, fMRI were input to 3dgo sczhry workstation for image fusion and 3D reconstruction. Spatial relationships between the lesions and the surrounding structures on the virtual reality image were obtained. These images were applied to the operative approach design, operation process simulation, intraoperative auxiliary decision and the training of specialist physician. Results: Intraoperative founding of 10 patients were highly consistent with preoperative simulation with virtual reality technology. Preoperative 3D reconstruction virtual reality images improved the feasibility of operation planning and operation accuracy. This technology had not only shown the advantages for neurological function protection and lesion resection during surgery, but also improved the training efficiency and effectiveness of dedicated physician by turning the abstract comprehension to virtual reality. Conclusion: Image fusion and 3D reconstruction based virtual reality technology in glioma resection is helpful for formulating the operation plan, improving the operation safety, increasing the total resection rate, and facilitating the teaching and training of the specialist physician.

Few-Layer Antimonene: Anisotropic Expansion and Reversible Crystalline-Phase Evolution Enable Large-Capacity and Long-Life Na-Ion Batteries

Two-dimensional (2D) antimonene is a promising anode material in sodium-ion batteries (SIBs) because of its high theoretical capacity of 660 mAh g^-1 and enlarged surface active sites. However, its Na storage properties and sodiation/desodiation mechanism have not been fully explored. Herein, we propose the sodiation/desodiation reaction mechanism of 2D few-layer antimonene (FLA) based on results acquired by in situ synchrotron X-ray diffraction, ex situ selected-area electron diffraction, and theoretical simulations. Our study shows that the FLA undergoes anisotropic volume expansion along the a/b plane and exhibits reversible crystalline phase evolution (Sb ⇋ NaSb ⇋ Na₃Sb) during cycling. Density-functional theory calculations demonstrate that the FLA has a small Na-ion diffusion barrier of 0.14 eV. The FLA delivers a larger capacity of 642 mAh g^-1 at 0.1 C (1 C = 660 mA g^-1) and a high rate capability of 429 mAh g^-1 at 5 C and maintains a stable capacity of 620 mA g^-1 at 0.5 C with 99.7% capacity retention from the 10th to the 150th cycle. Considering the 660 mAh g^-1 theoretical capacity of Sb, the electrochemical utilization of Sb atoms of FLA is as high as 93.9% at a rate of 0.5 C for over 150 cycles, which is the highest capacity and Sb utilization ratio reported so far. Our study discloses the Na storage mechanism of 2D FLA, boosting promising applications of 2D materials for advanced SIBs.

Flexible Nb₄N5/rGO Electrode for High-Performance Solid State Supercapacitors

Flexible supercapacitors (SCs) are desirable for elastic and clothing electronic products owning to their considerable safety, high foldability and outstanding power density. Herein, multilayered films composed of alternating mesoporous Nb4N5 nanobelts and rGO nanosheets (Nb4N5/rGO) are designed and fabricated exhibiting good flexibility. The folding Nb4N5/rGO film electrode reveals an areal capacitance of 141 mF cm-2 (at 1 mA cm-2) along with remarkable cycling stability (the capacitance retention is 90% after 6,000 cycles). The flexible SCs devices were constructed by interlayer couple films of Nb4N5/rGO electrodes with PVA/H2SO4 gel as the electrolyte, which exhibited huge volumetric capacitance of 19 F cm-3 (at 0.1 A cm-3) and a considerable energy density of 0.98 mW h cm-3 with a power density of 0.029 W cm-3. Additionally, the as-obtained folding devices bode outstanding cycling stability with capacitance retention of 89% after 4,000 cycles measured by cyclic voltammetry method (at 100 mV s-1). Above results about niobium nitride based flexible electrodes and devices exploit a platform for wearable electronics and flexible devices.

Silver-loaded nanotubular structures enhanced bactericidal efficiency of antibiotics with synergistic effect in vitro and in vivo

Antibiotic-resistant bacteria have become a major issue due to the long-term use and abuse of antibiotics in treatments in clinics. The combination therapy of antibiotics and silver (Ag) nanoparticles is an effective way of both enhancing the antibacterial effect and decreasing the usage of antibiotics. Although the method has been proved to be effective in vitro, no in vivo tests have been carried out at present. Herein, we described a combination therapy of local delivery of Ag and systemic antibiotics treatment in vitro in an infection model of rat. Ag nanoparticle-loaded TiO₂ nanotube (NT) arrays (Ag-NTs) were fabricated on titanium implants for a customized release of Ag ion. The antibacterial properties of silver combined with antibiotics vancomycin, rifampin, gentamicin, and levofloxacin, respectively, were tested in vitro by minimum inhibitory concentration (MIC) assay, disk diffusion assay, and antibiofilm formation test. Enhanced antibacterial activity of combination therapy was observed for all the chosen bacterial strains, including gram-negative Escherichia coli (ATCC 25922), gram-positive Staphylococcus aureus (ATCC 25923), and methicillin-resistant Staphylococcus aureus (MRSA; ATCC 33591 and ATCC 43300). Moreover, after a relative short (3 weeks) combinational treatment, animal experiments in vivo further proved the synergistic antibacterial effect by X-ray and histological and immunohistochemical analyses. These results demonstrated that the combination of Ag nanoparticles and antibiotics significantly enhanced the antibacterial effect both in vitro and in vivo through the synergistic effect. The strategy is promising for clinical application to reduce the usage of antibiotics and shorten the administration time of implant-associated infection.

In situ fabrication of Ni nanoparticles on N-doped TiO2 nanowire arrays by nitridation of NiTiO3 for highly sensitive and enzyme-free glucose sensing

A novel strategy for Ni NPs/TiO_xN_y NWAs by nitridation of NiTiO₃ NWAs is designed for highly sensitive and selective non-enzymatic glucose sensing.

Dominant Factors Governing the Electron Transfer Kinetics and Electrochemical Biosensing Properties of Carbon Nanofiber Arrays

Carbon-based electrodes have been widely used in electroanalysis for more than half a century, but the factors governing the heterogeneous electron-transfer (HET) rate are still unclear. The effects of the exposed edge plane site density, inherent resistance of the carbon electrode, and adjustable resistors on the HET kinetics of several outer- and inner-sphere redox couples including [Fe(CN)₆]^3-/4-, Ru(NH₃)₆^3+/2+, Fe^3+/2+, dopamine, ascorbic acid, and uric acid are investigated using three kinds of carbon electrodes composed of core-shell quasi-aligned nanofiber arrays (QANFAs). The internal resistance is found to be a key factor affecting the HET kinetics and electrochemical biosensing properties. The electrodes exhibit high selectivity and sensitivity in dopamine detection in the presence of ascorbic acid and uric acid. In addition to the promising application to electrochemical biosensing, the core-shell TiC/C QANFAs encompassing a highly electroactive carbon shell and conductive TiC core provide insights into the design and construction of the ideal carbon electrode.

High-energy lithium-ion hybrid supercapacitors composed of hierarchical urchin-like WO3/C anodes and MOF-derived polyhedral hollow carbon cathodes

A lithium-ion hybrid supercapacitor (Li-HSC) comprising a Li-ion battery type anode and an electrochemical double layer capacitance (EDLC) type cathode has attracted much interest because it accomplishes a large energy density without compromising the power density. In this work, hierarchical carbon coated WO₃ (WO₃/C) with a unique mesoporous structure and metal-organic framework derived nitrogen-doped carbon hollow polyhedra (MOF-NC) are prepared and adopted as the anode and the cathode for Li-HSCs. The hierarchical mesoporous WO₃/C microspheres assembled by radially oriented WO₃/C nanorods along the (001) plane enable effective Li⁺ insertion, thus exhibit high capacity, excellent rate performance and a long cycling life due to their high Li⁺ conductivity, electronic conductivity and structural robustness. The WO₃/C structure shows a reversible specific capacity of 508 mA h g^-1 at a 0.1 C rate (1 C = 696 mA h g^-1) after 160 discharging-charging cycles with excellent rate capability. The MOF-NC achieved the specific capacity of 269.9 F g^-1 at a current density of 0.2 A g^-1. At a high current density of 6 A g^-1, 92.4% of the initial capacity could be retained after 2000 discharging-charging cycles, suggesting excellent cycle stability. The Li-HSC comprising a WO₃/C anode and a MOF-NC cathode boasts a large energy density of 159.97 W h kg^-1 at a power density of 173.6 W kg^-1 and 88.3% of the capacity is retained at a current density of 5 A g^-1 after 3000 charging-discharging cycles, which are better than those previously reported for Li-HSCs. The high energy and power densities of the Li-HSCs of WO₃/C//MOF-NC render large potential in energy storage.

Mesoporous TiO2 Nanocrystals/Graphene as an Efficient Sulfur Host Material for High-Performance Lithium-Sulfur Batteries

Rechargeable lithium-sulfur (Li-S) batteries are promising in high-energy storage due to the large specific energy density of about 2600 W h kg(-1). However, the low conductivity of sulfur and discharge products as well as polysulfide-shuttle effect between the cathode and anode hamper applications of Li-S batteries. Herein, we describe a novel and efficient S host material consisting of mesoporous TiO2 nanocrystals (NCs) fabricated in situ on reduced graphene oxide (rGO) for Li-S batteries. The TiO2@rGO hybrid can be loaded with 72 wt % sulfur. The strong chemisorption ability of the TiO2 NCs toward polysulfide combined with high electrical conductivity of rGO effectively localize the soluble polysulfide species within the cathode and facilitate electron and Li ions transport to/from the cathode materials. The sulfur-incorporated TiO2@rGO hybrid (S/TiO2@rGO) shows large capacities of 1116 and 917 mA h g(-1) at the current densities of 0.2 and 1 C (1 C = 1675 mA g(-1)) after 100 cycles, respectively. When the current density is increased 20 times from 0.2 to 4 C, 60% capacity is retained, thereby demonstrating good cycling stability and rate capability. The synergistic effects of TiO2 NCs toward effective chemisorption of polysulfides and conductive rGO with high electron mobility make a promising application of S/TiO2@rGO hybrid in high-performance Li-S batteries.

Strontium (Sr) and silver (Ag) loaded nanotubular structures with combined osteoinductive and antimicrobial activities

Two frequent problems are associated with the titanium surfaces of bone/dental implants: lack of native tissue integration and associated infection. These problems have prompted a significant body of research regarding the modification of these surfaces. The present study describes a hydrothermal treatment for the fabrication of strontium (Sr) and silver (Ag) loaded nanotubular structures with different tube diameters on titanium surfaces. The Sr loading from a Sr(OH)2 solution was regulated by the size of the inner diameter of the titanium nanotubes (NT) (30nm or 80nm, formed at 10V or 40V, respectively). The quantity of Ag was adjusted by immersing the samples in 1.5 or 2.0M AgNO3 solutions. Sr and Ag were released in a controllable and prolonged matter from the NT-Ag.Sr samples, with negligible cytotoxicity. Prominent antibacterial activity was observed due to the release of Ag. Sr incorporation enhanced the initial cell adhesion, migration, and proliferation of preosteoblast MC3T3-E1 cells. Sr release also up-regulated the expression of osteogenic genes and induced mineralization, as suggested by the presence of more mineralized calcium nodules in cells cultured on NT-Ag.Sr surfaces. In vivo experiments showed that the Sr-loaded samples accelerated the formation of new bone in both osteoporosis and bone defect models, as confirmed by X-ray, Micro-CT evaluation, and histomorphometric analysis of rats implanted with NT-Ag.Sr samples. The antibacterial activity and outstanding osteogenic properties of NT-Ag.Sr samples highlight their excellent potential for use in clinical applications.

STATEMENT OF SIGNIFICANCE

Two frequent problems associated with Ti surfaces, widely used in orthopedic and dental arenas, are their lack of native tissue integration and risk of infection. We describe a novel approach for the fabrication of strontium (Sr) and silver (Ag) loaded nanotubular structures on titanium surfaces. A relevant aspect of this work is the demonstration of long-lasting and controllable Ag release, leading to excellent antibacterial and anti-adherent properties against methicillin-resistant Staphylococcus aureus (MRSA), and Gram-negative bacteria such as Escherichia coli. The extended release of Sr accelerates the filling of bone defects by improving the repair of damaged cortical bone and increasing trabecular bone microarchitecture. Our results highlight the potential of Sr and Ag loaded nanotubular structures for use in clinical applications.

3D Hierarchical Bi2S 3 Nanostructures by Polyvinylpyrrolidone (PVP) and Chloride Ion-Assisted Synthesis and Their Photodetecting Properties

A solvothermal method has been employed to synthesize bismuth sulfide (Bi2S3) with three-dimensional (3D) hierarchical architectures. The influences of different types of surfactants and Cl(-) species on the size and morphology were investigated. A possible formation mechanism was also proposed on the basis of time-dependent experiments. The photoresponse properties show that the conductivity of Bi2S3 micro-flowers is significantly enhanced and the photocurrent is approximately two orders of magnitude larger than the dark current. The response and decay times are estimated to be 142 and 151 ms, respectively. It is expected that hierarchical architectures Bi2S3 may provide a new pathway to develop advanced nanomaterial for high-speed and high-sensitivity photoelectrical switches and photodetecting devices.

Mitigation of Corrosion on Magnesium Alloy by Predesigned Surface Corrosion

Rapid corrosion of magnesium alloys is undesirable in structural and biomedical applications and a general way to control corrosion is to form a surface barrier layer isolating the bulk materials from the external environment. Herein, based on the insights gained from the anticorrosion behavior of corrosion products, a special way to mitigate aqueous corrosion is described. The concept is based on pre-corrosion by a hydrothermal treatment of Al-enriched Mg alloys in water. A uniform surface composed of an inner compact layer and top Mg-Al layered double hydroxide (LDH) microsheet is produced on a large area using a one-step process and excellent corrosion resistance is achieved in saline solutions. Moreover, inspired by the super-hydrophobic phenomenon in nature such as the lotus leaves effect, the orientation of the top microsheet layer is tailored by adjusting the hydrothermal temperature, time, and pH to produce a water-repellent surface after modification with fluorinated silane. As a result of the trapped air pockets in the microstructure, the super-hydrophobic surface with the Cassie state shows better corrosion resistance in the immersion tests. The results reveal an economical and environmentally friendly means to control and use the pre-corrosion products on magnesium alloys.