Ion implantation into collagen-coated surfaces for the development of small diameter artificial grafts

Ion implantation into collagen (Type I) coated inner surfaces of test tubes with a length of 50 mm and an inner diameter of 2 and 3 mm were performed to develop hybrid type small diameter artificial vascular grafts. To obtain information about the cellular response and chemical and physical structure of those collagen surfaces, several experiments such as platelets adhesion test, endothelial cell culture, analysis of amino acids and animal study were performed. He(+) ion implanted collagen coated specimen exhibited cell attachment and inhibit platelet adhesion. From these results, it was assumed that He(+) ions broke the ligands that correspond to platelet, and the ligands that correspond to endothelial cell adhesion still existed after ion implantation. It was suggested that platelets and cell attachment could be control individually by ion implantation into collagen.     

Patterning Surfaces for Controlled Platelet Adhesion and Detection of Dysfunctional Platelets

Platelets play a fundamental role in thrombus formation and in the pathogenesis of arterial thrombosis. Patterning surfaces for controlled platelet adhesion paves the way for adhesion and activation mechanisms in platelets and detection of platelet functional defects. Here, a new and simple method based on controlled polymerization of 2‐methacryloyloxyethyl phosphorylcholine (MPC) on the surface of styrene‐block‐(ethylene‐co‐butylene)‐block‐styrene (SEBS) is shown. The competition between polymerization and degradation enables platelet adhesion on SEBS to be switched on and off. The adhesive sites of the platelets can be down to single cell level, and the dysfunctional platelets can be quantitatively detected.

     

Surfactant-assisted alignment of ZnO nanocrystals to superstructures

Self-organization of ZnO nanoparticles into various superstructures (sheet, platelet, ring) has been achieved with the assistance of micelles formed by surfactant cetyltrimethylammonium bromide (CTAB) under one-pot condition. The CTAB-modified zinc hydroxy double salt (Zn-HDS) mesocrystals act as intermediates to form ZnO hexagonal superstructures at temperatures as low as 50 degrees C. The decomposition temperature of Zn-HDS mesocrystals is much lower than that of the corresponding bulk crystals because the organic additive CTAB effectively decreases the degree of crystallinity. Taking advantage of temperature-induced phase transformation of micelles, two-stage self-organization can form ZnO platelets and ring mesocrystals, that is, ZnO ellipsoidal superstructures formed through vertical attachment on (0001) facets of basic units can further assemble to form ZnO platelets and rings through vertical attachment on (0001) facets of ZnO ellipsoidal superstructures. The structural transformation of micelles as shape templates can offer a new route for self-assembly of nonspherical colloids into three-dimensional photonic crystals. ZnO sheet, ring, and platelet mesocrystals with a high population of polar Zn-(0001) plane are expected to have high photocatalytic activity.     

Formation of Highly Aligned Collagen Nanofibers by Continuous Cyclic Stretch of a Collagen Hydrogel Sheet

A collagen sheet with highly aligned collagen fibers is fabricated by continuous cyclic stretch. The rearrangement of the collagen fibers depends on the different process parameters of the cyclic stretch, including magnitude, frequency, and period of stretch. The collagen fibers are aligned perpendicularly to the direction of the stretch. Corneal stromal cells and smooth muscle cells cultivated on the highly aligned collagen sheet show alignment along the collagen fibers without the stretch during culture. Thus, the sheet can be a suitable scaffold for use in regenerative medicine.

     

The expression and role of protein kinase C in neonatal cardiac myocyte attachment, cell volume, and myofibril formation is dependent on the composition of the extracellular matrix.

The extracellular matrix (ECM) is a dynamic component of tissues that influences cellular phenotype and behavior. We sought to determine the role of specific ECM substrates in the regulation of protein kinase C (PKC) isozyme expression and function in cardiac myocyte attachment, cell volume, and myofibril formation. PKC isozyme expression was ECM substrate specific. Increasing concentrations of the PKC delta inhibitor rottlerin attenuated myocyte attachment to randomly organized collagen (1, 5, and 10 microM), laminin (5 and 10 microM), aligned collagen (5 and 10 microM), and fibronectin (10 microM). Rottlerin significantly decreased cell volume on laminin and randomly organized collagen, and inhibited myofibril formation on laminin. The PKC alpha inhibitor G? 6976 inhibited attachment to randomly organized collagen at 6 nM but did not affect cell volume. The general PKC inhibitor Bisindolylmalemide I (10 and 30 microM) did not affect myocyte attachment; however, it significantly decreased cell volume on randomly organized collagen. Our data indicate that PKC isozymes are expressed and utilized by neonatal cardiac myocytes during attachment, cell growth, and myofibril formation. Specifically, it appears that PKC delta and/or its downstream effectors play an important role in the interaction between cardiac myocytes and laminin, providing further evidence that the ECM influences cardiac myocyte behavior.     

Synthesis and Characterization of Fluorescent Silica Nanoparticles Functionalized with Collagens of Variable Lengths

Collagen, the most abundant protein in human body, has been widely used as an excellent natural material for diverse biomedical applications due to its superior properties such as ample biological interaction sites, minimal immunogenicity and high biocompatibility. Collagens of different lengths are produced by recombinant technology and utilized to functionalize fluorescent silica nanoparticles (FNPs). The collagen‐functionalized FNPs display mono‐disperse distribution, but their sizes are dependent on the length of collagen. These modified FNPs all show nice fluorescence profile as well as low cytotoxicity, suggesting promising applications in bioimaging. We have demonstrated that various types of collagen, conveniently produced by recombinant technology, can be used to modify silica nanoparticles with nice characteristics such as mono‐dispersion, non‐interference in fluorescence and low toxicity. It may endow fluorescent silica nanoparticles with broad biological applications.     

Application of analytical isotachophoresis in the study of platelet membrane proteins in patients with chronic myeloproliferative disorders

The supernatants of dispase-treated platelets from normal persons and patients with myeloproliferative disorders were analysed by capillary isotachophoresis. The examined myeloproliferative disorders were three cases of chronic myelogeneous leukemia, one case of chronic neutrophilic leukemia, one case of essential thrombocythemia and one case of polycythemia vera. An additional peak was revealed in the samples from the patients with chronic myelogeneous leukemia. Platelets from the other three patients showed no additional bands. Isotachophoresis will be useful not only to analyse the superficial peptide on the cell membrane but also to define the peptide associated with malignant transformation.     

Synthesis of macromolecular prodrugs of procaine, histamine and isoniazid

The attachment of various drugs bearing -NH2 groups to poly-alpha,beta-aspartic acid as a biodegradable carrier afforded in good yields macromolecular prodrugs which were characterized with respect to composition and drug load by spectroscopic and analytical methods. N-Ethyl-N'-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) in an aqueous medium proved to be useful in the attachment reaction. Isoniazid, procaine and histamine were covalently coupled as pendant groups onto poly-alpha,beta-aspartic acid via an amide bond. In principle, controlled release of the aforementioned drugs can be achieved by biodegradation of the polymer or by cleavage of covalently bound polymer-drug conjugates.     

Irreversible adsorption of triple-helical soluble collagen monomers from solution to glass and other surfaces

The adsorption from various solutions of triple-helical soluble collagen monomers to solid surfaces was studied by labeling the collagen with ¹²⁵1. Adsorption to glass, siliconized glass, and Teflon, from aqueous solutions at various pH and ionic strength, was determined at collagen concentrations from 2 to 25 μg/ml. Adsorption was shown to be irreversible and little dependent on pH and ionic strength but increasing enormously as the surface is made more hydrophobic. Surface denaturation of the collagen by heat results in a substantial loss of material. The kinetics of adsorption suggest that the adsorption process may be selective and that not all collagen molecules which reach the surface are immediately adsorbed. Checking these results with earlier measurements of adsorbed layer thickness, a model for collagen adsorption is proposed.     

Ultralong Hydroxyapatite Nanowire/Collagen Biopaper with High Flexibility,Improved Mechanical Properties and Excellent Cellular Attachment

Highly flexible hydroxyapatite/collagen (HAP/Col) composite membranes are regarded to be significant for guided bone regeneration application owing to their similar chemical composition to that of natural bone, excellent bioactivity and good osteoconductivity. However, the mechanical strength of the HAP/Col composite membranes is usually weak, which leads to difficult surgical operations and low mechanical stability during the bone healing process. Herein, highly flexible ultralong hydroxyapatite nanowires/collagen (UHANWs/Col) composite biopaper sheets with weight fractions of UHANWs ranging from 0 to 100 % are facilely synthesized. The UHANWs are able to weave with each other to construct a three‐dimensional fabric structure in the collagen matrix, providing a strong interaction between UHANWs and an intermolecular force between UHANWs and the collagen matrix. The as‐prepared UHANWs/Col composite biopaper exhibits improved mechanical properties and high flexibility. More importantly, the as‐prepared highly flexible 70 wt % UHANWs/Col composite biopaper exhibits an excellent cytocompatibility and outstanding cellular attachment performance as compared with the pure collagen and 70 wt % HAP nanorods/Col membranes. In consideration of its superior mechanical properties and outstanding cellular attachment performance, the as‐prepared UHANWs/Col composite biopaper is promising for applications in various biomedical fields such as guided bone regeneration.     

Atomistic Simulation Study of Calcium,Phosphate and Fluoride Ion Association to the Teleopeptide‐Tails of Collagen – Initial Steps to Biomineral Formation

The attachment of single ions to putative adsorption sites in the tails of collagen fibers is investigated by means of molecular dynamics simulations and discussed with respect to the very early steps of apatite/collagen biomineral formation. Our studies clearly demonstrate an increased flexibility of the tails of the triple‐helical collagen protein. Apart from the termini of the backbone, several side chains were also observed to be freely accessible to ion attachment from aqueous solution. The teleopeptide was systematically scanned for suitable adsorption sites for calcium, phosphate and fluoride ions. Association of these ions was then explored from potential of mean force calculations. The resulting energy profiles reveal a variety of favorable protein‐ion bonds and hint at the suitability of the collagen tails to promote apatite aggregation.     

Use of electron density critical points as chemical function-based reduced representations of pharmacological ligands

In this paper, we propose a reduced representation of molecules of pharmacological interest based on their chemical functions. The proposed representations of the molecules are obtained by a topological analysis of their electron density maps at medium resolution, leading to graphs of critical points. The distribution of the different types of critical points are compared at various levels of resolution for a training set of 22 molecules in order to define the optimal resolution level leading to the best representation of the various chemical functions. The reduced representations can in the future be used for molecular similarity research and pharmacophore proposals.     

Cell docking inside microwells within reversibly sealed microfluidic channels for fabricating multiphenotype cell arrays

We present a soft lithographic method to fabricate multiphenotype cell arrays by capturing cells within an array of reversibly sealed microfluidic channels. The technique uses reversible sealing of elastomeric polydimethylsiloxane (PDMS) molds on surfaces to sequentially deliver various fluids or cells onto specific locations on a substrate. Microwells on the substrate were used to capture and immobilize cells within low shear stress regions inside channels. By using an array of channels it was possible to deposit multiple cell types, such as hepatocytes, fibroblasts, and embryonic stem cells, on the substrates. Upon formation of the cell arrays on the substrate, the PDMS mold could be removed, generating a multiphenotype array of cells. In addition, the orthogonal alignment and subsequent attachment of a secondary array of channels on the patterned substrates could be used to deliver fluids to the patterned cells. The ability to position many cell types on particular regions within a two dimensional substrate could potentially lead to improved high-throughput methods applicable to drug screening and tissue engineering.     

Modeling of the influence of conformation,isotopic substitution,and aqueous environment on the vibrational spectrum of L-glutamic acid

Quantum-mechanical calculations of optimized structures, harmonic force fields, and vibrational spectra were performed for 10 L-glutamic acid conformers. The vibrational spectra were interpreted using B3LYP/6-31+G** calculations for the stablest conformer. Satisfactory agreement between the experimental and theoretical data was obtained. Vibrational frequency shifts caused by isotopic substitution of various types in the L-glutamic acid molecule were analyzed taking into account the conformational structure and the influence of water medium and molecule ionization. Isotopic tags are suggested that can be used in biochemical studies taking into account their special characteristics.     

Binding strength of sodium ions in cellulose for different water contents

The interaction strength of sodium ions (Na(+)) with cellulose is investigated from first principles for varying degrees of water content. We find that the interaction of water molecules and Na(+) can be studied independently at the various OH groups in cellulose which we categorize as two different types. In the absence of water, Na(+) forms strong ionic bonds with the OH groups of cellulose. When water molecules are anchored to the OH groups via hydrogen bonds, Na(+) can eventually no longer bind to the OH groups, but will instead interact with the oxygen atoms of the water molecules. Due to the rather weak attachment of the latter to the OH groups, Na(+) becomes effectively more mobile in the fully hydrated cellulose framework. The present study thus represents a significant step toward a first-principles understanding of the experimentally observed dependence of ionic conductivity on the level of hydration in cellulose network.     

Fabrication and vibration characterization of electrically triggered shape memory polymer beams

Shape memory polymers (SMP) exhibit temperature, frequency and strain rate dependent properties which may be manipulated by various types of external stimuli to achieve desirable response characteristics. In recent years, the emphasis has been on designing SMPs which do not require external stimuli (such as a heat source) and have a rapid response time with large homogenous and reversible deformation characteristics. In this research, the fabrication process and dynamic vibration testing of an electrically activated SMP are presented. It is shown that conductive SMP beams can be fabricated to achieve tunable stiffness and damping with a reasonable thermal gradient generated by electrical triggering. This can allow the tuning of a range of frequency bandwidth and damping properties of SMPs for vibration control applications. The experimentation yielded modal properties (natural frequencies and damping) of the SMP beams. These parameters were validated against values obtained from the estimated performance of these beams based on the complex modulus parameters obtained using dynamic mechanical analysis (DMA). For a modest 20 °C temperature range in an epoxy based SMP, a resulting shift of approximately 7% in the natural frequency and 100% change in the damping ratio of a rectangular beam was successfully attained. These results recommend SMPs as being tunable materials that can enhance vibrational performance and expand the operational envelope of structures.     

Biosilicification Templated by Amphiphilic Block Copolypeptide Assemblies

An amphiphilic poly(L ‐lysine·HBr)‐block‐poly(L ‐leucine) (KL) diblock copolypeptide and its supramolecular assembly are used as a template to direct silica formation, which proceeds by a cooperative process involving biomimetic mineralization and copolypetide reassembly under ambient conditions. Various silica structures can be obtained by using different counterions, changing the chain length of the KL diblocks, and applying a sol–gel mineralization method. We find that the chain length of the KL diblock is an important factor in terms of controlling biosilica morphologies. We also find that the nature of the counterions strongly affects the resulting silica structures. For the same KL diblock, variation of anions from phosphate to sulfate and to carbonate can produce hexagonal silica platelets, silica rods, and fused silica platelets, respectively. In contrast, application of a sol–gel method can replicate the copolypeptide fibril network morphology in water, while employment of ultrasonication to the sol–gel medium transforms the silica fibrils to rigid silica rods. The resulting silica morphology has been systematically characterized using SEM and TEM, and the polypeptide conformation is explored using FT‐IR and CD spectroscopy.

     

The effect of green laser light irradiation on whole blood platelets

BACKGROUND: Laser light irradiation is assumed to have biostimulating effect in various cell types. However, there is still a lack of information concerning response of blood platelets to laser light irradiation. METHODS: In our study we used flow cytometry to monitor the effect of a green Nd-YAG laser (532 nm, 30 mW) irradiation on platelet activation and the expression of activated GPIIbIIIa glycoprotein complex (fibrinogen receptor) of whole blood platelets stained with fluorolabelled monoclonal antibody PAC-1. Also the formation of platelet microparticles and aggregates in a population of whole blood platelets following such irradiation was evaluated. RESULTS: Effects of laser light on platelet activation and reactivity were significant over a wide range of applied energies (p<0.01). While low and medium laser light energies (18 and 54 J) increased platelet activation, the irradiation with a high-energy laser light (108 J) resulted in depressed platelet reactivity and attenuated platelet response to activators. In addition, laser light irradiation had significant influence on the formation of platelet microparticles in either resting (p<0.05) or ADP-activated (p<0.05) platelets, while no significant effect was observed in collagen-activated platelets. On the other hand, laser light irradiation significantly increased the formation of platelet aggregates both in resting (p<0.01) and agonists-activated (p<0.05) platelets. CONCLUSIONS: Our results clearly point that the laser light irradiation of blood platelets can trigger signal transduction, leading to platelet activation, as well as the gradual loss of natural platelet reactivity and platelets' ability to respond to activating agents.     

Sequence‐specific nucleic acid mobility using a reversible block copolymer gel matrix and DNA amphiphiles (lipid‐DNA) in capillary and microfluidic electrophoretic separations

Reversible noncovalent but sequence‐dependent attachment of DNA to gels is shown to allow programmable mobility processing of DNA populations. The covalent attachment of DNA oligomers to polyacrylamide gels using acrydite‐modified oligonucleotides has enabled sequence‐specific mobility assays for DNA in gel electrophoresis: sequences binding to the immobilized DNA are delayed in their migration. Such a system has been used for example to construct complex DNA filters facilitating DNA computations. However, these gels are formed irreversibly and the choice of immobilized sequences is made once off during fabrication. In this work, we demonstrate the reversible self‐assembly of gels combined with amphiphilic DNA molecules, which exhibit hydrophobic hydrocarbon chains attached to the nucleobase. This amphiphilic DNA, which we term lipid‐DNA, is synthesized in advance and is blended into a block copolymer gel to induce sequence‐dependent DNA retention during electrophoresis. Furthermore, we demonstrate and characterize the programmable mobility shift of matching DNA in such reversible gels both in thin films and microchannels using microelectrode arrays. Such sequence selective separation may be employed to select nucleic acid sequences of similar length from a mixture via local electronics, a basic functionality that can be employed in novel electronic chemical cell designs and other DNA information‐processing systems.