Covalent immobilization of p-selectin enhances cell rolling

Cell rolling is an important physiological and pathological process that is used to recruit specific cells in the bloodstream to a target tissue. This process may be exploited for biomedical applications to capture and separate specific cell types. One of the most commonly studied proteins that regulate cell rolling is P-selectin. By coating surfaces with this protein, biofunctional surfaces that induce cell rolling can be prepared. Although most immobilization methods have relied on physisorption, chemical immobilization has obvious advantages, including longer functional stability and better control over ligand density and orientation. Here we describe chemical methods to immobilize P-selectin covalently on glass substrates. The chemistry was categorized on the basis of the functional groups on modified glass substrates: amine, aldehyde, and epoxy. The prepared surfaces were first tested in a flow chamber by flowing microspheres functionalized with a cell surface carbohydrate (sialyl Lewis(x)) that binds to P-selectin. Adhesion bonds between P-selectin and sialyl Lewis(x) dissociate readily under shear forces, leading to cell rolling. P-selectin immobilized on the epoxy glass surfaces exhibited enhanced long-term stability of the function and better homogeneity as compared to that for surfaces prepared by other methods and physisorbed controls. The microsphere rolling results were confirmed in vitro with isolated human neutrophils. This work is essential for the future development of devices for isolating specific cell types based on cell rolling, which may be useful for hematologic cancers and certain metastatic cancer cells that are responsive to immobilized selectins.     

Tailoring the trajectory of cell rolling with cytotactic surfaces

Cell separation technology is a key tool for biological studies and medical diagnostics that relies primarily on chemical labeling to identify particular phenotypes. An emergent method of sorting cells based on differential rolling on chemically patterned substrates holds potential benefits over existing technologies, but the underlying mechanisms being exploited are not well characterized. In order to better understand cell rolling on complex surfaces, a microfluidic device with chemically patterned stripes of the cell adhesion molecule P-selectin was designed. The behavior of HL-60 cells rolling under flow was analyzed using a high-resolution visual tracking system. This behavior was then correlated to a number of established predictive models. The combination of computational modeling and widely available fabrication techniques described herein represents a crucial step toward the successful development of continuous, label-free methods of cell separation based on rolling adhesion.     

Examining the lateral displacement of HL60 cells rolling on asymmetric P-selectin patterns

The lateral displacement of cells orthogonal to a flow stream by rolling on asymmetrical receptor patterns presents a new opportunity for the label-free separation and analysis of cells. Understanding the nature of cell rolling trajectories on such substrates is necessary to the engineering of substrates and the design of devices for cell separation and analysis. Here, we investigate the statistical nature of cell rolling and the effect of pattern geometry and flow shear stress on cell rolling trajectories using micrometer-scale patterns of biomolecular receptors with well-defined edges. Leukemic myeloid HL60 cells expressing the PSGL-1 ligand were allowed to flow across a field of patterned lines fabricated using microcontact printing and functionalized with the P-selectin receptor, leveraging both the specific adhesion of this ligand-receptor pair and the asymmetry of the receptor pattern inclination angle with respect to the fluid shear flow direction (α = 5, 10, 15, and 20°). The effects of the fluid shear stress magnitude (τ = 0.5, 1, 1.5, and 2.0 dyn/cm(2)), α, and P-selectin incubation concentration were quantified in terms of the rolling velocity and edge tracking length. Rolling cells tracked along the inclined edges of the patterned lines before detaching and reattaching on another line. The detachment of rolling cells after tracking along the edge was consistent with a Poisson process of history-independent interactions. Increasing the edge inclination angle decreased the edge tracking length in an exponential manner, contrary to the shear stress magnitude and P-selectin incubation concentration, which did not have a significant effect. On the basis of these experimental data, we constructed an empirical model that predicted the occurrence of the maximum lateral displacement at an edge angle of 7.5°. We also used these findings to construct a Monte Carlo simulation for the prediction of rolling trajectories of HL60 cells on P-selectin-patterned substrates with a specified edge inclination angle. The prediction of lateral displacement in the range of 200 μm within a 1 cm separation length supports the feasibility of label-free cell separation via asymmetric receptor patterns in microfluidic devices.     

Self‐Rolled Polymer Tubes: Novel Tools for Microfluidics,Microbiology, and Drug‐Delivery Systems

Recent work on the fabrication of tubular microstructures via self‐rolling of thin, bilayer polymer films is reviewed. A bending moment in the films arises due to the swelling of one component of the bilayer in a selective solvent. The inner diameters of the tubes vary from hundreds of nanometers to dozens of micrometers. The position of the tubes on the substrate and their length can be preset by photolithographic patterning of the bilayer. Prior to rolling, the bilayers can be exposed to different methods of surface functionalization, providing opportunities for engineering the microtube inner surfaces for use in microfluidic circuits and “microbiological” applications. The self‐rolling approach is promising for the development of novel drug‐ and cell‐delivery systems, as well as for tissue engineering.     

RO-heparin Inhibits L-Selectin-mediated Neutrophils Adhesion to Vascular Endothelium Under Flow Conditions

Introduction Migrationandrecruitmentofleukocytesfromblood toinflammatorylesionsitesaresequentiallyregulated byadhesionmoleculesandtheirreceptors[1].These lectinfamilyplaysamajorroleininitiatingattachement ofneutrophilstotheactivatedendothelium.P selectin,…     

Biomimetic technique for adhesion-based collection and separation of cells in a microfluidic channel

A basic step in many biological assays is separating and isolating different types of cells from raw samples. To better meet these requirements in microfluidic devices for miniature biomedical analytical systems, an alternative method for separating cells has been devised by mimicking the physiological process of leukocyte recruitment to blood vessel walls: adhesive cell rolling and transient tethering. Reproducing these interactions for cells on surfaces of microstructured fluidic channels can serve to capture and concentrate cells and even to fractionate different cell types from a continuously flowing sample. To demonstrate this principle, two designs for microstructured fluidic channels were fabricated: an array of Square pillars and another with slender, Offset pillars. These structures were coated with E-selectin IgG chimera and the interactions of HL-60 and U-937 cells with these structures were characterized. With inflow of fluidic cell suspensions, the structures were able to efficiently capture and arrest cells directly from the rapid free stream flow. After capture, cells transit through the channel in three phases: cell rolling, cell tethering, and transient re-suspension in free stream flow before re-capture. Under these interactions, captured cells were enriched several hundred-fold from the original concentration. Additionally, among collected cells, the difference in flow-driven, adhesion-mediated cell transit in the Square design suggested that the two cell types could at least be partially fractionated.     

Synthesis of the sialyl Lewis X epitope attached to glycolipids with different core structures and their selectin-binding characteristics in a dynamic test system

Sialyl Lewis X (sLeX)/selectin-mediated leukocyte rolling along endothelial cells has recently gained wide interest. In this paper the influence of the spacer length of laterally clustered neoglycolipids 1a-d on cell rolling in a dynamic test system is investigated. The required di-O-hexadecyl glycerols with none, and with three, six, or nine ethylene glycol units as spacer groups (compounds 4a-d) could be readily obtained. The synthesis of 1-O-thexyldimethylsilyl-protected sLeX 24 was based on sialylation of 2,3,4-O-unprotected galactose derivative 11 with sialyl phosphite 8 as donor; this afforded the desired disaccharide 12, which was transformed into trichloroacetimidate 14 as disaccharide donor. Reaction of 3-O-unprotected glucosamine derivative 18 with fucosyl donor 20 afforded disaccharide 21, which was transformed into the 4-O-unprotected derivative 23. Reaction of 14 with 23 furnished the desired tetrasaccharide 24 in good yield. Transformation of 24 into the trichloroacetimidate 26 as donor, followed by the reaction with 4a-d as acceptor gave, after deprotection, the target molecules 1a-d. For comparison, 4d was also connected with a sialyl residue (-->31) and with an N-acetylglucosamine residue (-->34). Compounds 1c and 1d with a hexaethylene glycol and a nonaethylene glycol spacer, respectively, were much more efficient in mediating selectin-dependent cell rolling in the dynamic test system than compounds 1a and 1b, which had no spacer (1a), or only a triethylene glycol spacer (1b).     

Approche méthodologique directe et continue du processus d'oxydation des bitumes par spectroscopie infrarouge à transformée de Fourier

(Direct continuous method for studying oxidation of bitumens by Fourier-transform infrared spectrometry). The method is based on the standard rolling thin-film oven test with oxidation in air at 163°C. A specially designed infrared cell is used. FTIR spectrometry provides spectral fingerprints which are characteristic for each bitumen.     

Synthetic glycoprotein mimics inhibit L-selectin-mediated rolling and promote L-selectin shedding

L-selectin is a leukocyte cell-surface protein that facilitates the rolling of leukocytes along the endothelium, a process that leads to leukocyte migration to a site of infection. Preventing L-selectin-mediated rolling minimizes leukocyte adhesion and extravasation; therefore, compounds that inhibit rolling may act as anti-inflammatory agents. To investigate the potential role of multivalent ligands as rolling inhibitors, compounds termed neoglycopolymers were synthesized that possess key structural features of physiological L-selectin ligands. Sulfated neoglycopolymers substituted with sialyl Lewis x derivatives (3',6-disulfo Lewis x or 6-sulfo sialyl Lewis x) or a sulfatide analog (3,6-disulfo galactose) inhibited L-selectin-mediated rolling of lymphoid cells. Functional analysis of the inhibitory ligands indicates that they also induce proteolytic release of L-selectin. Thus, their inhibitory potency may arise from their ability to induce shedding. Our data indicate that screening for compounds that promote L-selectin release can identify ligands that inhibit rolling.     

Modelling procedures and properties of rubber in rolling contact

Rubber covered cylinders in rolling contact are studied in two cases; rolling over a flat surface and rolling over a groove. In the first case, two different finite element procedures are compared for the purpose of investigating if computational savings can be made when taking amplitude dependent effects into account by using a modified viscoelastic steady state rolling procedure. This procedure is compared with using a more expensive overlay method with an elastoplastic-viscoelastic material model. The two procedures and material models are shown two give equal results in the flat surface case. For the case of rolling over a groove, it is shown how the non-linear dynamic material characteristics of the rubber layer influence the rolling contact. The groove filling capacity of the rubber is shown to be strongly dependent on the material model. It is shown that amplitude dependent rubber materials have better ability to fill out contact surface irregularities such as a groove.     

Symmetry and stability of nanotubes based on titanium dioxide

The process of rolling a monolayer of bulk crystal with biperiodical planar lattice to the nanotube was analyzed. It was shown by an example of the carbon nanotubes how the tube symmetry can be revealed through the analysis of symmetry of graphene layers (the layer group with a hexagonal planar lattice) and its changes at the rolling to form the tube. The developed approach can be used to analyze the symmetry of any nanotube. A computer program we developed is discussed that allows to determine the nanotube symmetry using the data on the symmetry and coordinates of the atoms in the nanolayer and get the coordinates of the atoms in the unit cell of the nanotube which can be used for the further quantum-chemical calculations. The method and results of ab initio calculations of the titanium dioxide monolayer stability in the LCAO basis optimized for the bulk crystal, using the hybrid exchange-correlation potential PBE0 are presented. Symmetry properties of nanotubes obtained by rolling the three- and six-plane monolayers (101) and (001) of anatase are discussed. Atomic and electronic structure of TiO₂ nanotubes found by geometry optimization is analyzed. It is shown that titanium dioxide nanotubes based on the three-plane monolayers with hexagonal and square lattice are approximately of the same stability. The data on the stability of nanotubes are essential for the synthesis of new nanomaterials based on titanium dioxide.     

TEXTURE AND CRYSTALLINITY EVOLUTION IN ISOTACTIC POLYPROPYLENE INDUCED BY ROLLING AND THEIR INFLUENCE ON MECHANICAL PROPERTIES

The orientation and crystallinity evolution of isotactic polypropylene （iPP） induced by rolling were studied using wide angle X-ray scattering with an area detector. The tensile mechanical properties of rolled isotactic polypropylene sheets were also measured in this work. The texture component method was used to analyze the rolling texture. The rolling texture consists mainly of （010）[001], （130）[001] and [001]//RD fiber components in the sample with a rolling true strain of 1.5. The results reveal that crystallinity drastically decreases during rolling. It is suggested that amorphization is a deformation mechanism which takes place as an alternative to crystallographic intralamellar slip depending on the orientation of the lamellae. Both the orientation and crystallinity affect the tensile mechanical properties of rolled polypropylene. Crystallinity influences the elastic modulus on both directions and yield strength on transverse direction at the first stage of deformation. Orientation is the main reason for the changes of mechanical properties, especially at the latter part of deformation. The changes of both tensile strength and elongation percentage on rolling direction are larger than those on transverse direction, which results from the orientation. At last, the anisotropic mechanical properties occur on the rolling and transverse direction： high tensile strength with low elongation percentage on rolling direction and low tensile strength with high elongation percentage on transverse direction.     

The crystal structure of poly(tetramethylene terephthalate)

The unit cell of poly(tetramethylene terephthalate) is triclinic with parameters a = 5.96 Å, b = 4.83 Å, c (fiber axis) = 11.62 Å, α = 115.2. β = 99.9, and γ = 111.3°; space group P1 , calculated crystalline density 1.41 g/cc. The plane of the benzene ring is found to be inclined by about 15° from the fiber axis, contributing to a shortening of the fiber period as compared to the period expected on the basis of analogy with other members of the terephthalate ester series. The remaining shortening of the fiber period occurs in the ? O? °CH₂? °CH₂? segment of the chain. No abnormally short distances among neighboring chain atoms were observed. A typical texture pattern was found in specimens of this polymer that were cold rolled and subsequently annealed. In this texture the c axis of the unit cell is highly oriented in the rolling direction; the a and b axes of the unit cell are oriented preferentially so that the terephthalate residue lies as close as possible to the plane of rolling.     

热轧对涂层导体用镍基带立方织构形成的影响

热机械加工制备的立方织构Ni及其合金带材广泛用于YBCO涂层导体的基带。涂层导体的制备要求基带具有强的立方织构和小的晶界角。通过在冷轧前进行热轧制备了强立方织构的镍基带。用三维取向分布函数（ODF）研究了轧制织构和再结晶织构，通过扫描电镜EBSD的观测，分析了晶粒取向分布和立方织构晶界微取向角分布。结果表明，冷轧前进行热轧有利于形成很强的立方织构和小的晶界微取向角。     

Evolution of near‐surface deformed layers during hot rolling of AA3104 aluminium alloy

In the present study, controlled reheating and breakdown rolling experiments have been carried out and the thickness, structure and uniformity of the resultant near‐surface deformed layer have been characterised by scanning and transmission electron microscopy. High aspect ratio rolling, coupled with an increased rolling speed and rough and worn roll surfaces results in a high degree of interaction between the work roll and work pieces. This generates a shingled surface appearance with a high population of transverse surface cracks and a relatively thick near‐surface deformed layer. In contrast, relatively low aspect ratio rolling, coupled with a reduced rolling speed and freshly ground work roll surfaces generates a relatively thin near‐surface deformed layer. The thickness of the near‐surface deformed layer varies across the alloy surface and is directly related to the shingles, the surface cracks and the distribution of coarse intermetallics. Copyright © 2009 John Wiley & Sons, Ltd.     

The Split Primer Ligation‐triggered 8‐17 DNAzyme Assisted Cascade Rolling Circle Amplification for High Specific Detection of Liver Cancer‐involved mRNAs: TK1 and c‐myc

Simultaneous detection of various intracellular biomarkers is promising for early diagnosis and treatment of cancer. Herein, we develop a novel method for high specific and ultrasensitive detection of liver cancer cell‐involved mRNAs: TK1 and c‐myc based on the split primer ligation‐triggered 8‐17 DNAzyme assisted cascade rolling circle amplification. Only two targets exist simultaneously, can trigger the rolling circle amplification to improve the accuracy and sensitivity. Meanwhile, an electrochemical molecular beacon, based on the host‐guest recognition between ferrocene groups and cucurbit urils [7] (CB[7]/Fc‐MB), is used to cause a “turn‐off” electrochemical signal which is decreased by disrupting its hairpin structure. Under the optimal conditions, the detection limit of TK1 and c‐myc mRNA is as low as 0.06 nM. Moreover, this method can be used to detect the TK1 and c‐myc mRNA in HepG2 cells and distinguish between cancer cells and their normal cells, proving that the method has the potential to detect the variation of biomarkers in vivo.     

Effect of tensile speed on mechanical characteristics of preliminary rolled polyethylene terephthalate films

The effect of tensile speed on the mechanical properties of amorphous polyethylene terephthalate films is studied. The films are oriented by rolling on laboratory rollers at room temperature. In the samples with the rolling degree of two, the subsequent tension with the velocity of 5 mm/min does not afford a neck. As the tensile speed increases to 500 mm/min, a neck results from instability of the deformation process, which is caused by the polymer heating. Upon high-speed tension, the temperature of the rolled samples exceeds the glass-transition point of polyethylene terephthalate. Despite the polymer heating, the rolling completely suppresses the formation of pores. The rolling leads to the delocalization of flow over the region of polymer transfer to the neck. While in the nonrolled films the flow occurs in the zone with the length on the order of the film thickness, after the rolling, the size of the flow zone increases, and the region with the length on the order of the film width is deformed.     

Rolling--a new application technique for luminescent bacteria on high-performance thin-layer chromatography plates

High-performance thin-layer chromatography (HPTLC) coupled with bioluminescence detection using Vibrio fischeri bacteria can be used for screening for unknown substances. This is accomplished by dipping the HPTLC plate in an aqueous bacteria solution. Especially polar substances, however, can start to dissolve during this process, which leads to blurring and tailing of the zones on the plate. To overcome this disadvantage, we applied the bacteria solution by rolling. This method has been described for chemical derivatizations, but is very rarely used. The rolling device was made of commercially available household articles. Using octhilinone and methylparaben as test compounds, rolling was compared with dipping. Despite of performing the rolling process manually, the results were reproducible. Depending on the substance and its amount on the HPTLC plate, peaks were narrower, up to a factor of 4 higher and with a higher signal-to-noise ratio than after dipping.     

液滴在超疏水形状记忆微阵列表面上定向/非定向滚动的可逆调控

利用3D打印、 模板赋形和表面修饰的方法, 制备出具有竖直结构的超疏水形状记忆微阵列. 该微阵列的竖直状态和倾斜状态能够基于形状记忆效应进行可逆调控. 当微阵列的结构发生改变, 液滴在表面的滚动状态也随之发生变化. 液滴在竖直的微阵列上表现出非定向滚动特征, 即液滴向微阵列两侧运动的滚动角是一致的. 在倾斜的微阵列上, 液滴则表现出定向运动的功能, 即液滴沿着微阵列倾斜方向上的滚动角要小于逆着阵列倾斜方向的滚动角. 因此, 本文通过调控微阵列形态实现了对液滴定向/非定向滚动的可逆调控.     

The shear viscosity of supercritical oxygen at high pressure

Shear viscosities of supercritical oxygen have been measured up to a pressure of 5.7 GPa at 294 K. A modified free-volume expression fits the data within 6% between the limits of the tenuous gas and 4.8 times the critical density. Nitrogen viscosities were found to correspond to those of oxygen through a simple scaling by critical constants. Viscosities were measured in the high-pressure diamond-anvil cell with a rolling-ball technique. The dynamics of a sphere rolling on an inclined plane were investigated in the context of these experiments. The effect of a second surface, situated above the sphere, was experimentally determined.