Dosage exploration of combined B-vitamin supplementation in stroke prevention: a meta-analysis and systematic review.

BACKGROUND: The optimal dosage range for B-vitamin supplementation for stroke prevention has not received sufficient attention. OBJECTIVE: Our aim was to determine the optimal dosage range of a combination of folic acid, vitamin B12, and vitamin B6 supplementation in stroke prevention. METHODS: We searched PubMed, the Cochrane Central Register of Controlled Trials, and Embase database for randomized controlled trials published between January 1966 and April 2023, whose participants received B-vitamin supplementation and that reported the number of stroke cases. Relative risk (RR) was used to measure the effect of combined supplementation on risk of stroke using a fixed-effects model. Risk of bias was assessed with the Cochrane risk-of-bias algorithm. RESULTS: The search identified 14 randomized controlled trials of folic acid combined with vitamin B12 and vitamin B6 supplementation for stroke prevention that included 76,664 participants with 2720 stroke cases. In areas without and with partial folic acid fortification, combined B-vitamin supplementation significantly reduced the risk of stroke by 34% [RR: 0.66; 95% confidence interval (CI): 0.50, 0.86] and 11% (RR: 0.89; 95% CI: 0.79, 1.00), respectively. Further analysis showed that a dosage of folic acid ≤0.8 mg/d and vitamin B12 ≤0.4 mg/d was best for stroke prevention (RR: 0.65; 95% CI: 0.48, 0.86) in these areas. In contrast, no benefit of combined supplementation was found in fortified areas (RR: 1.04; 95% CI: 0.94, 1.16). CONCLUSIONS: Our meta-analysis found that the folic acid combined with vitamin B12 and vitamin B6 supplementation strategy significantly reduced the risk of stroke in areas without and with partial folic acid fortification. Combined dosages not exceeding 0.8 mg/d for folic acid and 0.4 mg/d for vitamin B12 supplementation may be more effective for populations within these areas. This trial was registered at PROSPERO asCRD42022355077.

A Molecular Integrative Study on the Inhibitory Effects of WRR and ERW on Amyloid ß Peptide (1-42) Polymerization and Cell Toxicity.

Alzheimer's disease (AD) is a neurodegenerative disease and the main pathological characteristic of AD is the deposition of Aß42 in the brain. Inhibition of Aß42 polymerization is one of the important research directions. Due to the pathological complexity of Alzheimer's disease, studies on Aß42 polymerization inhibitors have not made significant progress worldwide. Using an independently constructed structure database of oligopeptides, in this study, molecular docking, umbrella sampling analysis of free energy, ThT fluorescence detection of Aß42 polymerization, transmission electron microscopy, and flow cytometry detection of reactive oxygen species (ROS) and apoptosis were performed to screen tripeptides and pentapeptides that inhibit polymerization. It was found that two tripeptides, i.e., WRR and ERW, bind stably to the core of Aß42 polymerization in the molecular dynamics analysis, and they significantly inhibited the aggregation of Aß42 and reduced their cell toxicity in vitro.

Nanoveneers: an electrochemical approach to synthesizing conductive layered nanostructures.

We report herein a facile electrochemical approach to synthesizing various layered composite films of nanomaterials and conducting polymers, called nanoveneers. Layered structures of polypyrrole film with single-walled carbon nanotubes (SWNTs), graphene, and Au nanoparticles have been obtained by electropolymerization of pyrrole molecules on a heavily doped silicon wafer preloaded with target conductive nanomaterials. A free-standing, transparent, and highly conductive composite film was achieved after peeling off from a silicon wafer. Different from traditional homogeneous composite materials, such kinds of nanoveneers combined to the best extent the structural continuity and processability of conducting polymers with the high conductivity and functionality of discontinuous SWNTs, graphene, and other nanomaterials. The layered electrochemical deposition provides a great freedom for constructing various nanostructures with well-controlled geometry and thus physicochemical properties, as demonstrated by SWNT/polypyrrole nanoveneers. These nanoveneers are particularly attractive in areas of chemical sensors, labels, transparent electronics, and optoelectronics.

Local gate effect of mechanically deformed crossed carbon nanotube junction.

In this work, we have demonstrated that the local deformation at the crossed carbon nanotube (CNT) junctions can introduce significant tunable local gate effect under ambient environment. Atomic force microscope (AFM) manipulation of the local deformation yielded a variation in transconductance that was retained after removing the AFM tip. Application of a large source-drain voltage and pressing the CNT junction above a threshold pressure can respectively erase and recover the transconductance modulation reversibly. The local gate effect is found to be independent of the length of the crossed CNT and attributed to the charges residing at the deformed junctions due to formation of localized states. The number of localized charges is estimated to be in the range of 10(2) to 10(3). These results may find potential applications in electromechanical sensors and could have important implications for designing nonvolatile devices based on crossed CNT junctions.

Unipolar p-type single-walled carbon nanotube field-effect transistors using TTF-TCNQ as the contact material.

We demonstrate herein that organic metal tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) can serve as an ideal material for source and drain electrodes to build unipolar p-type single-walled carbon nanotube (SWNTs) field-effect transistors (FETs). SWNTs were synthesized by the chemical vapor deposition (CVD) method on silicon wafer and then TTF-TCNQ was deposited by thermal evaporation through a shadow mask to form the source and drain contacts. An SiO2 layer served as the gate dielectric and Si was used as the backgate. Transfer characteristics show that these TTF-TCNQ contacted devices are Schottky barrier transistors just like conventional metal contacted SWNT-FETs. The most interesting characteristic of these SWNT transistors is that all devices demonstrate the unipolar p-type transport behavior. This behavior originates from the unique crystal structure and physical properties of TTF-TCNQ and this device may have potential applications in carbon nanotube electronics.

Electrochemical identification of metallic and semiconducting single-walled carbon nanotubes using the water gate effect.

By fabricating a PMMA control strip at the SWNTs-electrode contact area to screen off the water gate effect, metallic and semiconducting SWNTs were easily identified during the conventional electropolymerization process.

Selective positioning and integration of individual single-walled carbon nanotubes.

We present a general selective positioning and integration technique for fabricating single-walled carbon nanotube (SWNT) circuits with preselected individual SWNTs as building blocks by utilizing poly(methyl methacrylate) (PMMA) thin film as a macroscopically handlable mediator. The transparency and marker-replicating capability of PMMA mediator allow the selective placement of chirality-specific nanotubes onto predesigned patterned surfaces with a resolution of ca. 1 mum. This technique is compatible with multiple operations and p-n conversion by chemical doping, which enables the construction of complex and logic circuits. As demonstrations of building SWNTs circuits, we fabricated a field effect inverter, a 2 x 2 all-SWNT crossbar field effect transistor (FET), and flexible FETs on plastic with this technique. This selective positioning approach can also be extended to construct purpose-directed architecture with various nanoscale building blocks.

Creation of nanostructures with poly(methyl methacrylate)-mediated nanotransfer printing.

We demonstrate here a PMMA-mediated nanotransfer printing technique for reliably transferring nanoscale building blocks and sequentially building purpose-directed nanostructures. The utilization of PMMA film as a mediator introduced several features to this transfer approach, such as high efficiency, fidelity, universality, controllability, and multilevel transferability. Various nanostructures, such as an SWNTs-on-SAM structure, high-density crossbar array of SWNTs, a hybrid n-ZnO nanowire/p-SWNT cross-junction, a gold nanostructure-SAM-gold sandwich structure, a zigzag array of SWNTs, and gold nanobowl array were generated with this transfer approach. A metallic-semiconducting SWNT cross circuit was built to demonstrate its potential application in fabricating nanoelectronic devices. This technique paves the way to generate various structures with homo- or heterogeneous nanoscale building blocks, which facilitates exploring their fundamental properties and building novel devices.

Free-standing TiO(2) nanotube arrays made by anodic oxidation and ultrasonic splitting.

A facile and green method was employed to prepare large-scale free-standing TiO(2) nanotube (TNT) arrays, in which as-anodized TiO(2) nanotube films prepared in organic electrolytes with thickness ranging from seven to tens of micrometers were then ultrasonicated in a mix solution of ethanol and water. By controlling the ratio of ethanol to water, the time and the power of ultrasonication, large-scale free-standing TiO(2) nanotube arrays without any crack could be detached from the Ti substrates. Hydrogen sensing results demonstrated that the free-standing TNT film is more sensitive than a film with Ti substrates when exposed to 1000 ppm hydrogen ambient.

Simultaneous dielectrophoretic separation and assembly of single-walled carbon nanotubes on multigap nanoelectrodes and their thermal sensing properties.

By using the specifically designed multigap nanoelectrodes, we demonstrated an effective approach for the simultaneous dielectrophoretic separation and assembly of metallic and semiconducting single-walled carbon nanotubes (SWNTs). An approximate metallic-semiconducting-metallic multiarray structure was created by an inward-propagative sequential assembly of SWNTs under ac electric field. Such kinds of SWNT multiarray structures exhibited ultra-low-power consumption and excellent thermal sensing performances with the sensitivity being dependent on the number of gaps: the more gaps, the higher sensitivity. The effective separation of metallic and semiconducting tubes in different gaps is believed to be responsible for the improved sensitivity to temperature.

Controllable interconnection of single-walled carbon nanotubes under ac electric field.

We demonstrated the controllable interconnection of single-walled carbon nanotubes (SWNTs) under alternating current (ac) electric field. The interconnected carbon nanotubes were found to be parallel with the electric flux and increased abruptly with deposition time following a self-accelerating process. Theoretical simulation indicates that the alignment and the interconnection of carbon nanotubes were induced by the dielectrophoresis force and the electric field redistribution at the nanotube apexes.

Electric-field-enhanced assembly of single-walled carbon nanotubes on a solid surface.

We report a novel electric-field-enhanced chemical assembly approach for fabricating highly aligned SWNT arrays on a solid surface with remarkably improved efficiency and packing density, which is very important for the real applications of carbon nanotube arrays. With the enhancement of the electric field, the assembling kinetics of SWNTs is remarkably speeded up to effectively decrease the assembling time, and the packing density can even exceed the saturated density of conventional assembly method by four times within only half an hour. The molecular dynamics simulation results illustrated the alignment of SWNTs with their long axes along the electric flux in solution, leading to the increase of packing density and efficiency through overcoming the steric hindrance of the "giant" carbon nanotubes.