Lipid Bilayers on a Picoliter Microdroplet Array for Rapid Fluorescence Detection of Membrane Transport

This paper describes picoliter‐sized lipid bilayer chambers and their theoretical model for the rapid detection of membrane transport. To prepare the chambers, semispherical aqueous droplets are patterned on a hydrophilic/hydrophobic substrate and then brought into contact with another aqueous droplet in lipid‐dispersed organic solvent, resulting in the formation of the lipid bilayers on the semispherical droplets. The proposed method implements the lipid bilayer chambers with 25‐fold higher ratio of lipid membrane area (S) to chamber volume (V) compared to the previous spherical droplet chambers. Using these chambers, we are able to trace the time‐course of Ca²⁺ influx through α‐hemolysin pores by a fluorescent indicator. Moreover, we confirm that the detection time of the substrate transport is inversely proportional to the S/V ratio of the developed chambers, which is consistent with the simulation results based on the developed model. Our chambers and model might be useful for rapid functional analyses of membrane transport phenomena.     

Membrane Perturbation by Carbon Nanotube Insertion: Pathways to Internalization

Carbon nanotubes (CNTs) can penetrate the membranes of cells, offering prospects for nanomedicine but problems for nanotoxicity. Molecular simulations are used to provide a systematic analysis of the interactions of single‐walled and multi‐walled CNTs of different radii with a model lipid bilayer membrane. The simulations allow characterization of the mechanism of spontaneous exothermic insertion of CNTs into lipid bilayer membranes. The size and type of CNT determine the nature and extent of the local perturbation of the bilayer. Single‐walled CNTs are shown to insert via a two‐step mechanism with initial transient formation of a water filled pore followed by full insertion of the CNT into the bilayer. The latter stage is associated with formation of a persistent inverted micelle arrangement of lipid molecules trapped inside the CNT. This suggests a possible vehicle for nano‐encapsulation of drugs, enabling their entry into and subsequent release within cells following endocytosis of CNT‐containing membranes.     

Surface energy and separation mechanics of droplet interface phospholipid bilayers

Droplet interface bilayers are a convenient model system to study the physio-chemical properties of phospholipid bilayers, the major component of the cell membrane. The mechanical response of these bilayers to various external mechanical stimuli is an active area of research because of its implications for cellular viability and the development of artificial cells. In this article, we characterize the separation mechanics of droplet interface bilayers under step strain using a combination of experiments and numerical modelling. Initially, we show that the bilayer surface energy can be obtained using principles of energy conservation. Subsequently, we subject the system to a step strain by separating the drops in a step-wise manner, and track the evolution of the bilayer contact angle and radius. The relaxation time of the bilayer contact angle and radius along with the decay magnitude of the bilayer radius were observed to increase with each separation step. By analysing the forces acting on the bilayer and the rate of separation, we show that the bilayer separates primarily through the peeling process with the dominant resistance to separation coming from viscous dissipation associated with corner flows. Finally, we explain the intrinsic features of the observed bilayer separation by means of a mathematical model comprising the Young–Laplace equation and an evolution equation. We believe that the reported experimental and numerical results extend the scientific understanding of lipid bilayer mechanics, and that the developed experimental and numerical tools offer a convenient platform to study the mechanics of other types of bilayers.     

载体促进输送膜进展

本文从含载体膜的传质机制、栽体和膜材料的选择方面综述了载体促进输送膜的发展过程,着重介绍了载体促进输送膜在气体分离方面的进展。     

Transport and Deposition of Evaporating Droplets in a Ventilated Environment

In this study, droplet transport, dispersion, and deposition in a ventilated office with two manikins were studied using a computer-modeling approach. Different airflow distribution systems were used, and an Eulerian approach was employed for the airflow simulation. The trajectories of droplets were evaluated using the Lagrangian approach by solving the equation of droplet motion that included the inertial, viscous drag, Brownian, Saffman lift, and gravity forces. Droplet evaporation was also taken into account by solving the droplet heat and mass transfer equations, thus, allowing for the variation of the droplet size. Mixing and displacement air distribution systems were examined, and trajectories of droplets in the range of 1 to 100 microns emitted by one of the manikins were simulated under a range of conditions. The simulation results showed that the chance for small droplets to leave the room through the exhaust is relatively high. When the mixing air distribution system is used, the drop dispersion is higher than with the displacement distribution system. This in turn suggests that the chance of transmission of air borne diseases is relatively higher for the mixing ventilation system.     

支撑双层类脂膜电极的温度补偿方法

提出了一种基于支撑双层类脂膜（S-BLM）电导的电极过程温度补偿方法。利用S-BLM电导传感器测试系统,研究了S-BLM电导与温度的关系。在线性假设的前提下,用最小二乘参数估计法,推导了S-BLM电导传感器特性曲线的斜率、截距与温度的线性方程,进而根据传感器曲线特性得到了S-BLM电极过程的温度补偿模型,并给出了LabVIEW平台下的实现方法。通过对线性假设的效果检验及精度分析,以及通过温度补偿模型的实际测试,证实了本文提出方法的有效性和实用性。     

Intercellular Transport of Nanomaterials is Mediated by Membrane Nanotubes In Vivo

So‐called membrane nanotubes are cellular protrusions between cells whose functions include cell communication, environmental sampling, and protein transfer. It has been previously reported that systemically administered carboxyl‐modified quantum dots (cQDs) are rapidly taken up by perivascular macrophages in skeletal muscle of healthy mice. Expanding these studies, it is found, by means of in vivo fluorescence microscopy on the mouse cremaster muscle, rapid uptake of cQDs not only by perivascular macrophages but also by tissue‐resident cells, which are localized more than 100 μm distant from the closest vessel. Confocal microscopy on muscle tissue, immunostained for the membrane dye DiI, reveals the presence of continuous membranous structures between MHC‐II‐positive, F4/80‐positive cells. These structures contain microtubules, components of the cytoskeleton, which clearly colocalize with cQDs. The cQDs are exclusively found inside endosomal vesicles. Most importantly, by using in vivo fluorescence microscopy, this study detected fast (0.8 μm s^?1, mean velocity), bidirectional movement of cQDs in such structures, indicating transport of cQD‐containing vesicles along microtubule tracks by the action of molecular motors. The findings are the first to demonstrate membrane nanotube function in vivo and they suggest a previously unknown route for the distribution of nanomaterials in tissue.     

Strategically Constructed Bilayer Tin (IV) Oxide as Electron Transport Layer Boosts Performance and Reduces Hysteresis in Perovskite Solar Cells

Nanostructured tin (IV) oxide (SnO₂) is emerging as an ideal inorganic electron transport layer in n–i–p perovskite devices, due to superior electronic and low‐temperature processing properties. However, significant differences in current–voltage performance and hysteresis phenomena arise as a result of the chosen fabrication technique. This indicates enormous scope to optimize the electron transport layer (ETL), however, to date the understanding of the origin of these phenomena is lacking. Reported here is a first comparison of two common SnO₂ ETLs with contrasting performance and hysteresis phenomena, with an experimental strategy to combine the beneficial properties in a bilayer ETL architecture. In doing so, this is demonstrated to eliminate room‐temperature hysteresis while simultaneously attaining impressive power conversion efficiency (PCE) greater than 20%. This approach highlights a new way to design custom ETLs using functional thin‐film coatings of nanomaterials with optimized characteristics for stable, efficient, perovskite solar cells.     

Nanodiamond‐Mediated Intercellular Transport of Proteins through Membrane Tunneling Nanotubes

Recently discovered tunneling nanotubes (TNTs) are capable of creating intercellular communication pathways through which transport of proteins and other cytoplasmic components occurs. Intercellular transport is related to many diseases and nanotubes are potentially useful as drug‐delivery channels for cancer therapy. Here, we apply fluorescent nanodiamond (FND) as a photostable tracker, as well as a protein carrier, to illustrate the transport events in TNTs of human cells. Proteins, including bovine serum albumin and green fluorescent protein, are first coated on 100‐nm FNDs by physical adsorption and then single‐particle tracking of the bioconjugates in the transient membrane connections is carried out by fluorescence microscopy. Stop‐and‐go and to‐and‐fro motions mediated by molecular motors are found for the active transport of protein‐loaded FNDs trapped in the endosomal vehicles of human embryonic kidney cells (HEK293T). Quantitative analysis of the heterotypical transport between HEK293T and SH‐SY5Y neuroblastoma cells by flow cytometry confirm the formation of open‐ended nanotubes between them, despite that their TNTs differ in structural components. Our results demonstrate the promising applications of this novel carbon‐based nanomaterial for intercellular delivery of biomolecular cargo down to the single‐particle level.     

Regulating Li-Ion Transport through Ultrathin Molecular Membrane to Enable High-Performance All-Solid-State–Battery

Solid-state lithium metal batteries with garnet-type electrolyte provide several advantages over conventional lithium-ion batteries, especially for safety and energy density. However, a few grand challenges such as the propagation of Li dendrites, poor interfacial contact between the solid electrolyte and the electrodes, and formation of lithium carbonate during ambient exposure over the solid-state electrolyte prevent the viability of such batteries. Herein, an ultrathin sub-nanometer porous carbon nanomembrane (CNM) is employed on the surface of solid-state electrolyte (SSE) that increases the adhesion of SSE with electrodes, prevents lithium carbonate formation over the surface, regulates the flow of Li-ions, and blocks any electronic leakage. The sub-nanometer scale pores in CNM allow rapid permeation of Li-ions across the electrode–electrolyte interface without the presence of any liquid medium. Additionally, CNM suppresses the propagation of Li dendrites by over sevenfold up to a current density of 0.7 mA cm⁻² and enables the cycling of all-solid-state batteries at low stack pressure of 2 MPa using LiFePO₄ cathode and Li metal anode. The CNM provides chemical stability to the solid electrolyte for over 4 weeks of ambient exposure with less than a 4% increase in surface impurities.     

Facilitate Gas Transport through Metal‐Organic Polyhedra Constructed Porous Liquid Membrane

Type II porous liquids are demonstrated to be promise porous materials. However, the category of porous hosts is very limited. Here, a porous host metal–organic polyhedra (MOP‐18) is reported to construct type II porous liquids. MOP‐18 is dissolved into 15‐crown‐5 as an individual cage (5 nm). Both the molecular dynamics simulations and experimental gravimetric CO₂ solubility test indicate that the inner cavity of MOP‐18 in porous liquids is unoccupied by 15‐crown‐5 and is accessible to CO₂. Thus, the prepared porous liquids show enhanced gas solubility. Furthermore, the prepared porous liquid is encapsulated into graphene oxide (GO) nanoslits to form a GO‐supported porous liquid membrane (GO‐SPLM). Owing to the empty cavity of MOP‐18 unit cages in porous liquids that reduces the gas diffusion barrier, GO‐SPLM significantly enhances the permeability of gas.     

Iontophoretic Transport of Model Compounds from a Gel Matrix Across a Cellophane Membrane

Drug release rates from hydrogels through cellophane membranes were determined using custom-built diffusion cells which were modified to allow the application of current across the membranes. In the absence of a current the results obtained using different concentrations of drug and of the gel indicate the release to be matrix-controlled with a linear relationship between the quantities of drug released and the square root of release time. When a range of direct currents was applied enhanced transport was observed and as the current was increased the release curves became linear with time. The rate of release was also found to increase linearly with the current strength. These results show that an electrical current may be used to increase the rate of drug transport and to alter its release profile under conditions when the unassisted release is matrix rather than membrane controlled.     

Iontophoretic Transport of Model Compounds from a Gel Matrix Across a Cellophane Membrane

Abstract

Drug release rates from hydrogels through cellophane membranes were determined using custom-built diffusion cells which were modified to allow the application of current across the membranes. In the absence of a current the results obtained using different concentrations of drug and of the gel indicate the release to be matrix-controlled with a linear relationship between the quantities of drug released and the square root of release time. When a range of direct currents was applied enhanced transport was observed and as the current was increased the release curves became linear with time. The rate of release was also found to increase linearly with the current strength. These results show that an electrical current may be used to increase the rate of drug transport and to alter its release profile under conditions when the unassisted release is matrix rather than membrane controlled.     

Zwitterionic Nanohydrogels–Decorated Microporous Membrane with Ultrasensitive Salt Responsiveness for Controlled Water Transport

Highly sensitive responsiveness is vital for stimuli‐responsive membranes. However, it is a great challenge to fabricate stimuli‐responsive membranes with ultrahigh gating ratio (the ratio of the salt solution permeating flux to the pure water permeating flux) and high response speed simultaneously. In this work, a salt‐responsive membrane with an ultrahigh gating ratio is fabricated via a facile strategy by grafting zwitterionic nanohydrogels onto a poly(acrylic acid)‐grafting‐poly(vinylidene fluoride) (PAA‐g‐PVDF) microporous membrane. Due to the synergistic effect of two functional materials, PAA chains and zwitterionic nanohydrogels tethered on PAA chains, this stimuli‐responsive membrane exhibits an ultrasensitive salt responsiveness with a gating ratio of up to 8.76 times for Na⁺ ions, 89.6 times for Mg²⁺ ions, and 89.3 times for Ca²⁺ ions. In addition, such zwitterionic nanohydrogels–grafted PAA‐g‐PVDF (ZNG‐g‐PVDF) membranes exhibit very rapid responses to stimuli. The permeating flux changes swiftly while altering the feed solution in a continuous filtration process. The excellent salt‐responsive characteristics endow such a ZNG‐g‐PVDF membrane with great potential for applications like drug delivery, water treatment, and sensors.     

脉冲MIG焊熔滴过渡最佳方式的控制

基于一个脉冲过渡一个熔滴且熔滴体积不变的思想,提出了在峰值电流和基值电流不变的条件下采用送丝速度预置和峰值弧压调节峰值时间与基值时间的控制方式。试验结果表明:采用这种控制方式,能够在不同送丝速度或不同干伸长下实现一个脉冲过渡一个熔滴且熔滴体积基本不变。