Vesicles in Nature and the Laboratory: Elucidation of Their Biological Properties and Synthesis of Increasingly Complex Synthetic Vesicles

The important role of vesicles in many aspects of cell function is well‐recognized, but only recently have sophisticated imaging techniques begun to reveal their ubiquity in nature. While we further our understanding of the biological properties of vesicles and their physiological functions, increasingly elegant artificial vesicles are being developed for a wide range of technological applications and basic research. Herein, we examine the state of the art of biological and synthetic vesicles and place their biological features in the context of recent synthetic developments, thus providing a unique overview of these complex and rapidly developing fields. The challenges and opportunities associated with future biological and synthetic studies of vesicles are also presented.     

水凝胶仿生柔性电子学

水凝胶力学性质与生物组织相似,生物相容性好,在生物电子学领域具有独特的优势.受生物组织——如皮肤、神经、肌肉等启发,发展了具有仿生结构和功能的水凝胶材料.以这种水凝胶材料制作而成的柔性电子器件具有感知温度、压力、应变、电场等外界刺激的功能,可模拟生物组织的传感能力,在仿生电子皮肤,人工肌肉,人工神经等领域具有重要的应用...     

Electrophoretic transport and dynamic deformation of bio‐vesicles

Study of the deformation dynamics of cells and other sub‐micron vesicles, such as virus and neurotransmitter vesicles are necessary to understand their functional properties. This mechanical characterization can be done by submerging the vesicle in a fluid medium and deforming it with a controlled electric field, which is known as electrodeformation. Electrodeformation of biological and artificial lipid vesicles is directly influenced by the vesicle and surrounding media properties and geometric factors. The problem is compounded when the vesicle is naturally charged, which creates electrophoretic forcing on the vesicle membrane. We studied the electrodeformation and transport of charged vesicles immersed in a fluid media under the influence of a DC electric field. The electric field and fluid‐solid interactions are modeled using a hybrid immersed interface‐immersed boundary technique. Model results are verified with experimental observations for electric field driven translocation of a virus through a nanopore sensor. Our modeling results show interesting changes in deformation behavior with changing electrical properties of the vesicle and the surrounding media. Vesicle movement due to electrophoresis can also be characterized by the change in local conductivity, which can serve as a potential sensing mechanism for electrodeformation experiments in solid‐state nanopore setups.     

Degradation and stabilisation of blue water pipe

Degradation caused by natural and artificial exposure of blue polyethylene water pipe compounds has been studied using thermal, spectroscopic and mechanical testing techniques. The results indicate that whilst thermal properties can be used as an effective quality control tool, deterioration of mechanical properties corresponds rather more with carbonyl index measurements. Samples in thin and thick sections have been studied and differences in behaviour are noted, with thick section samples retaining mechanical (impact) properties even after substantial degradation has occurred.

Limitations in the use of artificial exposure to monitor changes that occur during natural weathering are discussed. It is concluded that, in thick section, the surface nature of ultraviolet degradation in the extreme conditions of artificial exposure affects mechanical properties in a different manner than longer-term periods of natural exposure.     

Chemically encapsulated structural elements for probing the mechanical responses of biologically inspired systems

A living cell has a crowded environment with a dense distribution of molecules that requires structured organization for its efficient functioning. One component of this structure, the actin cytoskeleton, is essential for providing mechanical support and facilitating many response activities, including the contraction of muscle cells and chemotaxis. Whereas many investigations have provided insight into the mechanical response from either an in vivo or in vitro perspective, a significant gap exists in determining how the living cell response and the polymer physics response are bridged. The understanding of these systems involves studying their components, including the individual cytoskeletal elements versus the higher-order organism organization in a living cell. Here, we leverage this organization in nature by using a chemistry-based approach to mimic the cytoskeleton in an artificial environment composed of spherically distributed lipid bilayers. This construct bears similarities to the cell membrane. To create a structurally regulated environment, we encapsulate G-actin into giant unilamellar vesicles and then polymerize actin filaments within individual liposomes. We visualize these vesicles with epifluorescence microscopy and confocal microscopy. Atomic force microscopy is then used to probe the mechanical properties of these artificial cells. This polymer cytoskeletal network appears to connect with the lipid bilayer and span the internal space within the liposomes in a manner similar to what is observed in living cells. This work will have implications in a variety of fields, including chemistry, polymer physics, structural biology, and engineering mechanics.     

Engineering Polymersome Protocells

The field of biomimicry is embracing the construction of complex assemblies that imitate both biological structure and function. Advancements in the design of these mimetics have generated a growing vision for creating an artificial or proto- cell. Polymersomes are vesicles that can be made from synthetic, biological or hybrid polymers and can be used as a model template to build cell-like structures. In this perspective, we discuss various areas where polymersomes have been used to mimic cell functions as well as areas in which the synthetic flexibility of polymersomes would make them ideal candidates for a biomembrane mimetic. Designing a polymersome that comprehensively displays the behaviors discussed herein has the potential to lead to the development of an autonomous, responsive particle that resembles the intelligence of a biological cell.     

Hybrid organic–inorganic sol–gel materials for micro and nanofabrication

In this review hybrid organic–inorganic (HOI) resists as emerging materials alternative to organic polymers for micro and nanolithography are presented and discussed. In particular, results on sol–gel materials belonging to 3-glycidoxypropyltrimethoxysilane based HOI are presented and reviewed, highlighting as various lithographic techniques can be used to pattern their surface and showing examples of micro- and nano-patterned structures achieved with radiation assisted lithography (UV, X-rays and electron beam) or imprint techniques. It will be demonstrated the particular versatility shown by some of these materials, that in some case can be processed with all the lithographic methods herein considered, without any significant modification of their main composition and synthesis procedure. Moreover, results about the investigation of interaction between radiation and HOI materials and thermal treatment will be discussed, as well as possible synthesis strategies and composition modification developed in order to improve efficiency of curing, tailor HOI properties to specific needs (optical properties, resist composition, mechanical stability, etc.) and explore innovative and non conventional patterning techniques. The reported results highlight as these novel materials, thanks to their solution processability and higher performances respect to commercial polymeric resists, allow to use the above mentioned lithographic techniques in a direct patterning process, strongly simplifying conventional technique and reducing their processing time and costs.     

Cellular Membrane Components-Mediated Cancer Immunotherapeutic Platforms

Immune cell engineering is an active field of ongoing research that can be easily applied to nanoscale biomedicine as an alternative to overcoming limitations of nanoparticles. Cell membrane coating and artificial nanovesicle technology have been reported as representative methods with an advantage of good biocompatibility for biomimetic replication of cell membrane characteristics. Cell membrane-mediated biomimetic technique provides properties of natural cell membrane and enables membrane-associated cellular/molecular signaling. Thus, coated nanoparitlces (NPs) and artificial nanovesicles can achieve effective and extended in vivo circulation, enabling execution of target functions. While coated NPs and artificial nanovesicles provide clear advantages, much work remains before clinical application. In this review, first a comprehensive overview of cell membrane coating techniques and artificial nanovesicles is provided. Next, the function and application of various immune cell membrane types are summarized.     

烯碳材料改性有机高性能纤维：制备、性能及应用

有机高性能纤维是全球化纤工业的重要发展方向之一。提升现有纤维力学性能的同时研发新型结构功能一体化的纤维对提升我国在航天航空等领域的国际地位具有重要意义。以石墨烯和碳纳米管为代表的烯碳材料具备优异的力、电、热学等性能,可用于改性传统有机高性能纤维。通过制备不同物化性质的烯碳材料并设计合理的改性方式,可将烯碳材料优异的性能传递到传统纤维中,形成具备更高力、电、热学等性能的烯碳材料改性有机高性能纤维。本文首先综述了烯碳材料改性有机高性能纤维的制备方式,包括烯碳材料的分散与功能化、烯碳材料对有机高性能纤维的改性方法,阐述了烯碳材料改性有机高性能纤维的力、电、热学等性能以及烯碳材料的增强机理,进而总结了烯碳材料改性有机高性能纤维的应用,并对其现存的挑战和未来的发展做出展望。     

烯碳材料在人工肌肉领域的应用进展

随着仿生机器人、智能控制及人工智能等领域的发展,传统的机械驱动方式已无法满足相关领域对致动系统提出的柔性、高效及多源刺激响应性等要求,因此需发展新型的人工肌肉材料。以碳纳米管和石墨烯为代表的烯碳材料具有轻质、高强、高电导率和柔性等特征,在人工肌肉领域展现出了巨大的应用潜力。以烯碳材料为基元构筑宏观组装体材料,或以烯碳材料为添加相制备纳米复合材料,可在微观和宏观架起桥梁,实现烯碳材料在人工肌肉领域的应用。本文基于上述两种应用形式,综述了烯碳材料在人工肌肉领域的应用进展。首先从一维纤维和二维薄膜的烯碳人工肌肉宏观表现形态出发,介绍了既作为结构材料,又提供了响应、驱动功能的烯碳材料在人工肌肉中的应用。接着从机电性能、可编程的响应形变以及传感功能三个方向,介绍了烯碳材料作为增强赋能相在人工肌肉材料中的功能性应用。最后阐述了基于烯碳材料人工肌肉的机遇与挑战。     

Lipid vesicles in capillary electrophoretic techniques: characterization of structural properties and associated membrane-molecule interactions

This paper reviews the use of lipid vesicles as model membranes in capillary electrophoresis (CE). The history and utility of CE in the characterization of microparticles is summarized, focusing on the application of colloidal electromigration theories to lipid vesicles. For instance, CE experiments have been used to characterize the size, surface properties, enclosed volumes, and electrophoretic mobilities of lipid vesicles and of lipoprotein particles. Several techniques involving small molecules or macromolecules separated in the presence of lipid vesicles are discussed. Interactions between the analytes and the lipid vesicles - acting as a pseudostationary phase or coated stationary phase in electrokinetic chromatography (EKC) - can be used to obtain additional information on the characteristics of the vesicles and analytes, and to study the biophysical properties of membrane-molecule interactions in lipid vesicles and lipoproteins. Different methods of determining binding constants by EKC are reviewed, along with the relevant binding constant calculations and a discussion of the application and limitations of these techniques as they apply to lipid vesicle systems.     

On the short-time limit of ring polymer molecular dynamics

We examine the short-time accuracy of a class of approximate quantum dynamical techniques that includes the centroid molecular dynamics (CMD) and ring polymer molecular dynamics (RPMD) methods. Both of these methods are based on the path integral molecular dynamics (PIMD) technique for calculating the exact static equilibrium properties of quantum mechanical systems. For Kubo-transformed real-time correlation functions involving operators that are linear functions of positions or momenta, the RPMD and (adiabatic) CMD approximations differ only in the choice of the artificial mass matrix of the system of ring polymer beads that is employed in PIMD. The obvious ansatz for a general method of this type is therefore to regard the elements of the PIMD (or Parrinello-Rahman) mass matrix as an adjustable set of parameters that can be chosen to improve the accuracy of the resulting approximation. We show here that this ansatz leads uniquely to the RPMD approximation when the criterion that is used to select the mass matrix is the short-time accuracy of the Kubo-transformed correlation function. In particular, we show that the leading error in the RPMD position autocorrelation function is O(t(8)) and the error in the velocity autocorrelation function is O(t(6)), for a general anharmonic potential. The corresponding errors in the CMD approximation are O(t(6)) and O(t(4)), respectively.     

Biosurfactants: Formulations,properties, and applications

In this review, we attempt to give an overview on the recent progress made on biosurfactants, surface-active biomolecules produced by microorganisms, which are a sustainable alternative to synthetic surfactants. Different biosurfactants, their production techniques, and their physical and chemical properties are discussed. There is a focus on recent studies related to surface properties and rheology of biosurfactants, both being properties which affect their ability to take part in a stable formulation. Biosurfactants can have applications in multiple different industrial sectors, such as agriculture, medicine, personal care, food, petroleum, etc. The specific properties important for applications in these sectors are discussed in detail.     

Self‐Assembling Nanoparticles at Surfaces and Interfaces

Nanoparticles are the focus of much attention due to their astonishing properties and numerous possibilities for applications in nanotechnology. For realising versatile functions, assembly of nanoparticles in regular patterns on surfaces and at interfaces is required. Assembling nanoparticles generates new nanostructures, which have unforeseen collective, intrinsic physical properties. These properties can be exploited for multipurpose applications in nanoelectronics, spintronics, sensors, etc. This review surveys different techniques, currently employed and being developed, for assembling nanoparticles in to ordered nanostructures. In this endeavour, the principles and methods involved in the development of assemblies are discussed. Subsequently, different possibilities of nanoparticle‐based nanostructures, obtained in multi‐dimensions, are presented.     

Synergistic Covalent and Supramolecular Polymers for Mechanically Robust but Dynamic Materials

Nature has engineered delicate synergistic covalent and supramolecular polymers (CSPs) to achieve advanced life functions, such as the thin filaments that assist in muscle contraction. Constructing artificial synergistic CSP materials with bioinspired mechanically adaptive features, however, represents a challenging goal. Here, we report an artificial CSP system to illustrate the integration of a covalent polymer (CP) and a supramolecular polymer (SP) in a synergistic fashion, along with the emergence of notable mechanical and dynamic properties which are unattainable when the two polymers are formed individually. The synergistic effect relies on the peculiar network structures of the SP and CPs, which endow the resultant CSPs with overall improved mechanical performance in terms of the stiffness, strength, stretchability, toughness, and elastic recovery. Moreover, the dynamic properties of the SP, including self‐healing, stimuli‐responsiveness, and reprocessing, are also retained in the CSPs, thus leading to their application as programmable and tunable materials.     

Mechanical properties and stability measurement of cholesterol-containing liposome on mica by atomic force microscopy

The micromechanical properties of pure and cholesterol modified egg yolk phosphatidylcholine (EggPC) vesicles prepared by sonication were studied by atomic force microscopy (AFM) on mica surface. The force curves between an AFM tip and an unruptured vesicle were obtained by contact mode. During approach, two repulsion regions with two breaks were observed. The slopes of the two repulsive force regimes for the pure EggPC vesicles are determined to be several times lower than that of EggPC/cholesterol vesicles. The elastic properties from force plot analysis based on the Hertzian model showed that Young's modulus (E) and the bending modulus (kc) of cholesterol-modified vesicles increased several-fold compared with pure EggPC vesicles. The significant difference is attributed to the enhanced rigidity of the EggPC vesicles as a result of the incorporation of cholesterol molecules. The behavior of cholesterol-modified vesicles upon adsorption is different from that in solution as revealed by mechanical properties. The results indicate that AFM can provide a direct method to measure the mechanical properties of adsorbed small liposomes and to detect the stability change of liposomes.     

基于动物丝蛋白的人工纺丝

动物丝,特别是蜘蛛丝近年来由于其优异的综合力学性能而备受关注。但是天然动物丝的应用由于种种原因而受到各种限制,因此人们期望通过人工纺丝获得性能与天然动物丝相近的人工丝纤维。本文就采用动物丝蛋白进行人工纺丝的历史和现状,从再生蜘蛛丝蛋白、重组蜘蛛丝蛋白和再生蚕丝蛋白等方面进行综述,比较了天然动物丝和人工丝纤维的力学性能,并且探讨了人工生物模拟纺丝制备高性能人工丝纤维(超级纤维)的前景。     

Acoustics and atomic force microscopy for the mechanical characterization of thin films

The science and technology of thin films require the development of nondestructive methods for their quantitative mechanical characterization with nanometric spatial resolution. High-frequency ultrasonic techniques—especially acoustic microscopy—and atomic force microscopy (AFM) have been demonstrated to represent versatile tools for developing such methods. In particular, in the last 15 years, the combination of AFM, which can probe the surface of a sample by applying ultralow loads (from micronewtons down to piconewtons) with a micromachined tip having an apex radius of a few nanometers, and ultrasonics techniques led researchers to develop some unique tools which allow one to perform not only spot measurements of the sample elastic modulus, but also to obtain both the qualitative imaging of mechanical properties and the quantitative mapping of the elastic modulus of the sample surface with nanometric lateral resolution. In the present review, firstly a brief overview of the main ultrasound-based techniques for thin film characterization is reported. Then, some of the ultrasonic AFM techniques are described, emphasizing their capability of retrieving maps of both the tip–sample contact stiffness and the sample elastic modulus. Although these techniques are less affected by the mechanical properties of the substrates than standard indentation tests, a method for the correction of the substrate effect in ultrathin films is reported in detail. Finally, by probing the mechanical properties of a small portion of the sample volume underneath the tip, we illustrate the techniques as tools for the qualitative and quantitative characterization of variations in the adhesion between a thin film and a buried interface, as well as for detecting subsurface defects, voids, cracks, and dislocations.     

仿生矿化增强材料

近年来,随着材料科学领域的发展,机械性能优异且具有特定功能的有机-无机复合材料成为了研究热点。而天然的生物矿化过程产生了在自然界中分布广泛、结构特征多样性、机械性能优异的天然生物矿物,比如牙齿、骨骼、珍珠、贝壳、海胆刺、海洋红虫颚等。这些天然复合增强材料中的矿化组织结构特点和矿化机理为仿生设计与合成具有特定结构、特定功能和优异机械性能的材料提供了理论依据。通过模拟天然过程的仿生矿化方法,利用有机基质调控无机矿物成核生长为固态矿物,最终能够定向组装具有特定有序结构和先进功能的有机-无机复合材料。本文主要综述了自然界中通过生物矿化过程得到的高强度、高韧性的天然复合增强材料,以及受生物矿化增强现象的启发,在化学与材料仿生矿化合成中出现的一些有机-无机复合的增强材料。