Assembled capsules transportation driven by motor proteins

An active biomimetic system by integrating kinesin motor, microtubule, and man-made biomimetic microcapsule has been constructed. Biomimetic microcapsules were fabricated by using the layer-by-layer technique and could serve as cargos in this active biomimetic system. Both of the hollow and filled capsules as cargos can be transported by kinesin motors along microtubules. It may help to create kinesin-powered complex hybrid micro- and nanodevices.     

Effect of Thermal Fatigue Loading on Tensile Behavior of H13 Die Steel with Biomimetic Surface

<正> Biomimetic surface is an effective ways to promote the performance grade and applied range of materials without alteringtheir substrate.Many improved properties such as resisting fatigue,enduring wear,etc,have been achieved by applyingbiomimetic morphology or structure to some engineering material surfaces.In this paper,aiming to reveal the relationshipbetween thermal cracking behavior and mechanical properties of engineering materials with biomimetic surface,biomimeticspecimens were fabricated using laser technique by imitating the heterogeneous structure on the surface of plant leaves.Theeffect of thermal fatigue cycling on the tensile properties of H13 die steel specimens with different surfaces (several types ofbiomimetic surfaces and a smooth surface) was compared and investigated.As a result,due to the coupling effects of themorphological features on the surface and the microstructure characteristics within unit zone,these specimens with biomimeticsurface exhibit remarkably enhanced Ultimate Tensile Strength (UTS) and 0.2% Yield Strength (YS) compared with referencespecimens while corresponding ductility remains largely unaffected even heightened,whether the thermal fatigue loads or not.The relative mechanisms leading to these improvements have been discussed.     

Problems of biomimetic chemistry]

The main goals of biomimetic chemistry have been formulated on the basis of the concept of biochemical organization. Biomimetic chemistry is defined as a science which employs the principles of biochemical organization (i. e., the principles of structural organization, functioning and regulation of biological systems at the levels corresponding to biomacromolecules, supramolecular complexes and subcellular structures) for the construction of artificial systems with predetermined properties or for conferring desired properties on natural biochemical systems with the help of artificial elements. The relationships between biomimetics and biochemical modelling are discussed. As examples of biomimetic systems, some enzymes entrapped into hydrated reverse micelles of a surfactant in an organic solvent and conjugates of proteins with polyalkylene oxidases are considered.     

A microbead array chemical sensor using capillary-based sample introduction: toward the development of an "electronic tongue"

The development of a micromachined fluidic structure for the introduction of liquid samples into a chip-based sensor array composed of individually addressable polymeric microbeads is presented. The micromachined structure consists of micromachined storage cavities combined with a covering glass layer that confines the microbeads and fluidic channels. In our sensor array transduction occurs via optical (colorimetric and fluorescence) changes to receptors and indicator molecules that are covalently attached to termination sites on the polymeric microbeads. Spectral data are acquired for each of the individual microbeads using a charged-coupled device (CCD) allowing for the near-real-time analysis of liquid sample. Hence the micromachined fluidic structure must allow for both optical access to the microbeads and fluid flow through the micromachined cavities that serve as the microreactors/analysis chambers. One of the key parts of the structure is a passive fluid introduction system driven only by capillary force. This simple means of fluid introduction realizes a compact device. The capillary flow on the inlet channel has been studied, and the responses of the microbeads (alizarin complexone) to a liquid sample have been characterized. The test results show that this system is useful in a micro-total-analysis-system (mu-TAS) and biomedical applications.     

细胞膜仿生修饰纳米粒肿瘤治疗的研究进展

大量研究证明,细胞膜仿生修饰通过将不同细胞膜包被于纳米粒表面,赋予纳米粒新的生物学功能.纳米粒被细胞膜仿生修饰后,获得了细胞膜表面丰富的蛋白质并保留了纳米粒的高载药能力,延长体内循环时间,使纳米粒具有逃避免疫系统,跨越各种生理屏障的能力.本文总结了近年来细胞膜仿生修饰纳米粒用于肿瘤治疗的最新进展,讨论了细胞膜仿生修饰纳...     

Flow in tubules due to ciliary activity

A simplified model for cilia-induced flows in tubules is presented. Each cilium is a long slender body which is constrained to move similar to its beat. An array of cilia is defined and coordinated in such a way as to represent the metachronal wave. The velocity field is represented by a distribution of viscous fluid singularities (Stokes flow) along the centerline of each slender body. The total mean velocity field due to all the cilia is obtained. It is found that backflow (reflux) can occur near the walls for cilia exhibiting antiplectic metachronism. Maximum flow rates are obtained for cilia whose length is 0.3 to 0.6 the radius of the tube.     

Lessons and revelations from biomimetic syntheses

Biomimetic synthesis describes the field of organic chemistry that aims to emulate the natural, biosynthetic processes toward natural products. As well as providing insight into how molecules are formed in nature, the benefits of this approach to total synthesis are numerous and extend beyond the gains typical of traditional synthesis. For example, using biosynthetic proposals to design a synthetic route can highlight alternative methods to the desired target. The pursuit of biomimetic syntheses also promotes the development of new reactions to prove or disprove a biosynthetic proposal or to unravel mechanistic implications of a proposed biosynthesis and can lead to the identification of new natural products. Here we look at some recent compelling examples and examine how biomimetic synthesis has led to the discovery of new procedures and principles that would not have been found by other approaches.     

HIF Stabilization Weakens Primary Cilia

Although solitary or sensory cilia are present in most cells of the body and their existence has been known since the sixties, very little is known about their functions. One suspected function is fluid flow sensing- physical bending of cilia produces an influx of Ca⁺⁺, which can then result in a variety of activated signaling pathways. Defective cilia and ciliary-associated proteins have been shown to result in cystic diseases. Autosomal Dominant Polycystic Kidney Disease (ADPKD) is a progressive disease, typically appearing in the 5^th decade of life and is one of the most common monogenetic inherited human diseases, affecting approximately 600,000 people in the United States. Because the mechanical properties of cilia impact their response to applied flow, we asked how the stiffness of cilia can be controlled pharmacologically. We performed an experiment subjecting cilia to Taxol (a microtubule stabilizer) and CoCl₂ (a HIF stabilizer to model hypoxia). Madin-Darby Canine Kidney (MDCK) cells were selected as our model system. After incubation with a selected pharmacological agent, cilia were optically trapped and the bending modulus measured. We found that HIF stabilization significantly weakens cilia. These results illustrate a method to alter the mechanical properties of primary cilia and potentially alter the flow sensing properties of cilia.     

Mathematical modelling of ciliary propulsion of an electrically-conducting Johnson-Segalman physiological fluid in a channel with slip

Bionic systems frequently feature electromagnetic pumping and offer significant advantages over conventional designs via intelligent bio-inspired properties. Complex wall features observed in nature also provide efficient mechanisms which can be utilized in biomimetic designs. The characteristics of biological fluids are frequently non-Newtonian in nature. In many natural systems super-hydrophobic slip is witnessed. Motivated by these phenomena, in this paper, we discussed a mathematical model for the cilia-generated propulsion of an electrically-conducting viscoelastic physiological fluid in a ciliated channel under the action of magnetic field. The rheological behavior of the fluid is simulated with the Johnson-Segalman constitutive model which allows internal wall slip. The regular or coordinated movement of the ciliated edges (which line the internal walls of the channel) is represented by a metachronal wave motion in the horizontal direction which generates a two-dimensional velocity profile. This mechanism is imposed by a periodic boundary condition which generates propulsion in the channel flow. Under the classical lubrication approximation, the boundary value problem is non-dimensionalized and solved analytically with a perturbation technique. The influence of the geometric, rheological (slip and Weissenberg number) and magnetic parameters on velocity, pressure gradient and the pressure rise (evaluated via the stream function in symbolic software) are presented graphically and interpreted at length.     

COST Action CM1201 “Biomimetic Radical Chemistry”: free radical chemistry successfully meets many disciplines

Abstract

The COST Action CM1201 “Biomimetic Radical Chemistry” has been active since December 2012 for 4 years, developing research topics organized into four working groups: WG1 – Radical Enzymes, WG2 – Models of DNA damage and consequences, WG3 – Membrane stress, signalling and defenses, and WG4 – Bio-inspired synthetic strategies. International collaborations have been established among the participating 80 research groups with brilliant interdisciplinary achievements. Free radical research with a biomimetic approach has been realized in the COST Action and are summarized in this overview by the four WG leaders.     

Cilia, KIF3 molecular motor and nodal flow

The establishment of left-right asymmetry during development of vertebrate embryos depends on leftward flow in the nodal cavity. The flow is produced by the rotational movement of the posteriorly tilted nodal cilia. However, it remains poorly understood how the nodal cilia are tilted posteriorly, and how the directionality of the flow is translated into gene expression patterns in the embryo. Recent studies have identified signaling molecules involved in these processes. First, planar cell polarity signaling has been shown to be involved in the posterior positioning of the basal bodies of nodal cilia, which leads to the posterior tilting of their rotation axes. Second, identification of putative receptors and signaling molecules suggests a link between the signaling molecules delivered by the nodal flow, and downstream signaling in the cells surrounding the nodal cavity and the lateral plate mesoderm.     

Primary cilia as biomechanical sensors in regulating endothelial function

Depending on the pattern of blood flow to which they are exposed and their proliferative status, vascular endothelial cells can present a primary cilium into the flow compartment of a blood vessel. The cilium modifies the response of endothelial cells to biomechanical forces. Shear stress, which is the drag force exerted by blood flow, is best studied in this respect. Here we review the structural composition of the endothelial cilia and the current status of knowledge about the relation between the presence of primary cilia on endothelial cells and the shear stress to which they are exposed.     

Spontaneous creation of macroscopic flow and metachronal waves in an array of cilia

Cells carrying cilia on their surface show many striking features: alignment of cilia in an array, two-phase asymmetric beating for each cilium, and existence of metachronal coordination with a constant phase difference between two adjacent cilia. We give simple theoretical arguments based on hydrodynamic coupling and an internal mechanism of the cilium derived from the behavior of a collection of molecular motors to account qualitatively for these cooperative features. Hydrodynamic interactions can lead to the alignment of an array of cilia. We study the effect of a transverse external flow and obtain a two-phase asymmetrical beating, faster along the flow and slower against the flow, proceeding around an average curved position. We show that an aligned array of cilia is able to spontaneously break the left-right symmetry and to create a global average flow. Metachronal coordination arises as a consequence of the internal mechanism of the cilia and their hydrodynamic couplings, with a wavelength comparable to that found in experiments. It allows the cilia to start beating at a lower adenosine-triphosphate threshold and at a higher frequency than for a single cilium. It also leads to a rather stationary flow, which might be its major advantage.     

Biomimetic cooperative interactions of dried cross-linked poly(N-6-aminohexylacrylamide) with binary mixtures of solvent vapors

Biomimetic cooperativity of hydration effect and effect of ethanol favorable for binding of bad organic sorbates were observed for their vapor sorption by cross-linked poly(N-6-aminohexylacrylamide) (PNAHAA) in the absence of liquid phase. The vapor sorption isotherms were determined for these systems by the static method of gas chromatographic headspace analysis at 298 K. The hydration above 0.09-0.13 g of H(2)O/(g of polymer) gives a cooperative increase in the PNAHAA binding affinity for benzene, cyclohexane, dioxane, and propanols up to a level which does not change by further hydration, indicating the polymer antiplasticization. Bad sorbates (dioxane, benzene) were observed to have a biomimetic cooperative influence on the binding of ethanol by the dried PNAHAA. This cooperativity does not occur in ternary systems with good nonhydroxylic sorbate acetonitrile.     

Bioinspired enzyme encapsulation for biocatalysis

Biocatalysis exploits the versatility of enzymes to catalyse a variety of processes for the production of novel compounds and natural products. Enzyme immobilization enhances the stability and hence applicability of biomolecules as reusable and robust biocatalysts. Biomimetic mineralization reactions have emerged as a versatile tool for generating excellent supports for enzyme stabilization. The methodology utilizes biological templates and synthetic analogues to catalyse the formation of inorganic oxides. Such materials provide biocompatible environments for enzyme immobilization. The utility of the method is further enhanced by entraining and attaching encapsulated catalysts to a variety of supports. This review discusses biomimetic and bioinspired mineral formation as a technique for the immobilization of enzymes with potential application to a wealth of biocatalytic processes.     

Abnormal nodal flow precedes situs inversus in iv and inv mice.

We examined the nodal flow of well-characterized mouse mutants, inversus viscerum (iv) and inversion of embryonic turning (inv), and found that their laterality defects are always accompanied by an abnormality in nodal flow. In a randomized laterality mutant, iv, the nodal cilia were immotile and the nodal flow was absent. In a situs inversus mutant, inv, the nodal cilia was motile but could only produce very weak leftward nodal flow. These results consistently support our hypothesis that the nodal flow produces the gradient of putative morphogen and triggers the first L-R determination event.     

Influence de la densité de peptides RGD greffés en surface de polyéthylène téréphtalate sur l’attachement des MC3T3

The aim of this study was to evaluate the impact of different densities on MC3T3 cells attachment onto polyethylene terephthalate (PET) film surfaces. Biomimetic modifications were performed by means of a three-step reaction procedure: creation of COOH functions onto PET surface, coupling agent grafting and finally immobilization of peptides. The originality of this work consist, in one hand on quantifying RGD peptides densities grafted onto PET, and on the other hand on studying MC3T3 cells responses after seeding on such biomimetic surfaces. After each functionnalization step, modifications were validated by several physicochemical techniques: X-Ray Photoelectron Spectroscopy permitted to prove the grafting and high-resolution β-imager coupled with use of radiolabelled amino acids served in evaluation of peptides densities. Moreover, this last technique permit us to ensure stability of binding between peptides and polymer. The efficiency of this new route for biomimetic modification of PET surface was demonstrated by measuring the adhesion at 15 hours of osteoblast like cells. Study of cellular comportment was realized by means of focal contact proteins (vinculin, actin) immunostaining.     

Biomimetic gel exhibiting self-beating motion in ATP solution

Biomimetic material systems using stimuli-responsive polymers and gels have been widely studied for applications to artificial muscles, drug delivery systems, biosensors, etc. In almost all cases, however, the action is driven by on-off switching of external signals. In contrast, here we show a novel biomimetic gel to exhibit autonomous self-beating motion in ATP solution under constant condition, similar to heart muscle. An anionic polymer gel with phosphoric groups, in which creatine kinase was immobilized, was prepared. When the gel was immersed in the ATP solution, the enzymatic reaction occurs in the gel and the concentration of calcium ion changes periodically. Since the chelates between phosphoric groups and the divalent calcium ion, which acts a physical crosslinking point, are formed and dissociated periodically, the gel repeats swelling and deswelling autonomously.     

Pkd1l1 complexes with Pkd2 on motile cilia and functions to establish the left-right axis

The internal organs of vertebrates show distinctive left-right asymmetry. Leftward extracellular fluid flow at the node (nodal flow), which is generated by the rotational movement of node cilia, is essential for left-right patterning in the mouse and other vertebrates. However, the identity of the pathways by which nodal flow is interpreted remains controversial as the molecular sensors of this process are unknown. In the current study, we show that the medaka left-right mutant abecobe (abc) is defective for left-right asymmetric expression of southpaw, lefty and charon, but not for nodal flow. We identify the abc gene as pkd1l1, the expression of which is confined to Kupffer's vesicle (KV, an organ equivalent to the node). Pkd1l1 can interact and interdependently colocalize with Pkd2 at the cilia in KV. We further demonstrate that all KV cilia contain Pkd1l1 and Pkd2 and left-right dynein, and that they are motile. These results suggest that Pkd1l1 and Pkd2 form a complex that functions as the nodal flow sensor in the motile cilia of the medaka KV. We propose a new model for the role of cilia in left-right patterning in which the KV cilia have a dual function: to generate nodal flow and to interpret it through Pkd1l1-Pkd2 complexes.