Increase In Adhesive Properties Research Articles

A Novel Bio-Adhesive Based on Chitosan-Polydopamine-Xanthan Gum for Glass, Cardboard and Textile Commodities.

The escalating environmental concerns associated with petroleum-based adhesives have spurred an urgent need for sustainable alternatives. Chitosan, a natural polysaccharide, is a promising candidate; however, its limited water resistance hinders broader application. The aim of this study is to develop a new chitosan-based adhesive with improved properties. The polydopamine association with chitosan presents a significant increase in adhesiveness compared to pure chitosan. Polydopamine is synthesized by the enzymatic action of laccase from Trametes versicolor at pH = 4.5, in the absence or presence of chitosan. This pH facilitates chitosan's solubility and the occurrence of catechol in its reduced form (pH < 5.5), thereby increasing the final adhesive properties. To further enhance the adhesive properties, various crosslinking agents were tested. A multi-technique approach was used for the characterization of formulations. The formulation based on 3% chitosan, 50% polydopamine, and 3% xanthan gum showed a spectacular increase in adhesive properties when tested on glass, cardboard and textile. This formulation increased water resistance, maintaining the adhesion of a sample soaked in water for up to 10 h. For cardboard and textile, material rapture occurred, in mechanical tests, prior to adhesive bond failure. Furthermore, all the samples showed antiflame properties, expanding the benefits of their use. Comparison with commercial glues confirms the remarkable adhesive properties of the new formulation.

Novel acrylic/nanocellulose microsphere with improved adhesive properties

A synthesis of acrylic microsphere pressure sensitive adhesives with addition of nanocellulose filler is presented. In the first stage α cellulose was modified by acid hydrolysis and the produced nanocellulose suspension was added into the continuous phase of a suspension polymerization reaction mixture. The amount of nanocellulose varied in range from 0wt% (reference synthesis) to 5wt% calculated on monomer amount. The first part of the study was assigned to the characterization of the synthesized adhesive suspension. Particle sizes and particle size distributions were measured. Then, adhesives were coated via a transfer coating process and adhesive properties were evaluated. Additionally, polymer glass transition temperatures were determined and due to significant differences in measured adhesive properties, adhesive viscoelastic properties were examined using dynamic mechanical analysis (DMA). Results showed that it's possible to use nanocellulose as a nanofiller in microsphere adhesives. Suspensions were stable, mean particle sizes decreased with increasing nanocellulose content mainly due to a higher continuous phase viscosity. Adhesive properties testing revealed non typical behavior for the nanocomposite microsphere PSA material. All three measured adhesive properties increased with increasing nanocellulose content. A synergistic effect of lower particle sizes along with hydrogen bonding exhibited an increase in adhesive properties. DMA analysis showed that the storage modulus (G') increased with increasing amount of added nanocellulose. At the same time a decrease in maximal tan δ values was observed which concurred with improved cohesivity, hence higher shear strength.

Hemostasis in Erysipelas-The Reason for Considering Antithrombotic Therapy

The indices of external (prothrombin time, INR) and internal (activated partial prothrombin time (aTpp) coagulation pathways, the degree of disfibrinogenemia (thrombin time, functional fibrinogen activity and D-dimer level), the amount and functional activity of the platelets (aggregation with ADP) and the erythrocytes (aggregation with lanthanoid and protamine sulfate) were studied in 60 patients with erysipelas. Also, we have studied endothelial dysfunction manifested in the decrease of athrombogenicity of vascular wall endothelium (antithrombin III and protein C) and in the increase of adhesive properties of the endothelium (von Willebrand factor). The comparison groups comprised normal volunteers (n=32) and patients with focus of inflammation localized on the face (n=24), and the legs (n=36) at various stages of the disease (day 1–3; 4-6; 7-10; and 11-15 from the onset of the disease), undergoing in hospital treatment in Moscow 2nd Clinical Hospital for the Infectious Diseases. The thesis, according to which the rate of hemorrhagic complications in leg erysipelas is by 3,9 times higher than in facial erysipelas, was confirmed by laboratory findings. In particular, a significant decrease of protein C was noted in patients with leg erysipelas and concomitant chronic venous insufficiency. We have found increased D-dimer and decreased α2-macroglobulin levels, suggesting potent activation of proteolytic enzymes (plasmin, matrix metalloproteinases, neutrophil elastase), which can be one of the causes of bullae, erosion and ulceration formation in the erysipelas focus on the lower limb. The signs of intravascular (latent) hemolysis - the decrease of haptoglobin concentration and the increase of indirect bilirubin and LDH blood level; the changes of rheological properties of erythrocytes – the increase of deformability (aggregation with lanthanum chloride) and the decrease of elasticity (aggregation with protamine sulfate) – have been identified as one of the main factors for DIC-like syndrome in erysipelas.

Reactive Changes of Cytophysiological Properties, Molecular-Biological Profile and Functional Metabolic Status of Cells in Vitro with Different Sensitivity to Cytostatic Agents Under the Influence of Magnetic Fluid

The peculiarities of changes of phenotype properties in MCF-7 human breast cancer cells with different sensitivity to cytostatic agents under the influence of nanoparticles of magnetic fluid were studied. It is defined that the biggest manifestations of magnetic fluid effect both by its essence and direction are observed in cells of resistant MCF-7/Dox line and parental MCF-7/S line in comparison with MCF-7/CP (cisplatin-resistant cell line). In particular, these are more apparent cytotoxic effects and ability to colony-formation, increase of adhesive properties, decrease of invasiveness and proliferative activity, changes of surface charge density and electrokinetic potential as well as lipid composition of cells. The defined differences between MCF-7 cells with different sensitivity to cytostatic agents according to phenotypic manifestations of correlations (magnetic fluid effect – reactive response) are evidence of the individual peculiarities of free radicals formation in cells and development of oxidative stress. The indicated phenomenon of selective reactive changes in cells by effect of magnetic fluid is necessary to take into account in development of systems of directed transport of antitumor drugs.

C-terminal Modification of Osteopontin Inhibits Interaction with the αVβ3-Integrin

Osteopontin (OPN) is a multifunctional phosphorylated protein containing the integrin binding sequence Arg-Gly-Asp through which it interacts with several integrin receptors, such as the α(V)β(3)-integrin. OPN exists in many different isoforms differing in phosphorylation status that are likely to interact differently with integrins. The C-terminal region of OPN is particularly well conserved among mammalian species, which suggests an important functional role of this region. In this study, we show that modification of the extreme C terminus of OPN plays an important regulatory role for the interaction with the α(V)β(3)-integrin. It is demonstrated that highly phosphorylated OPN has a much reduced capability to promote cell adhesion via the α(V)β(3)-integrin compared with lesser phosphorylated forms. The cell attachment promoted by highly phosphorylated OPN could be greatly increased by both dephosphorylation and proteolytic removal of the C terminus. Using recombinantly expressed OPN containing a tag in the N or C terminus, it is shown that a modification in the C-terminal part significantly reduces the adhesion of cells to OPN via the α(V)β(3)-integrin, whereas modification of the N terminus does not influence the binding. The inhibited binding of the α(V)β(3)-integrin to OPN could be restored by proteolytic removal of the C terminus by thrombin and plasmin. These data illustrate a novel mechanism regulating the interaction of OPN and the α(V)β(3)-integrin by modification of the highly conserved C-terminal region of the protein.

Interaction Forces of a Supported DOPC Bilayer in the Presence of the General Anaesthetic Halothane — An Atomic Force Microscopy Study

In this study atomic force microscopy (AFM) was used to study the effect of halothane on a supported dioleoylphosphatidylcholine (DOPC) bilayer under conditions of high anaesthetic loading. In a previous study we demonstrated that bilayer restructuring occurs as a result of halothane incorporation. Force measurements using AFM indicate an initial decrease in adhesive forces and compressibility between the bilayer and AFM tip, followed by an increase in adhesion properties as a function of incubation time. This effect is attributed to the location and dynamic redistribution of halothane within the bilayer.

Surface Patterning and Adhesion of Neuroblastoma X Glioma (NG108-15) Cells

A variable height flow cell was used to measure the adhesion properties of the neural cell line of neuroblastoma X glioma (NG108-15) cells cultured on substrates of organosilane self-assembled monolayers (SAMs). The SAMs tested in this study were 13F, 15F, PEG 550, OTS, DETA and APTS. Utilizing deep UV lithography, patterning of the SAMs create three regions for cell attachment; the original SAM, the backfilled SAM, and the interface between the two. Upon plating, the cell soma show no preference for any of the three regions. One exception was on PEG 550, which was found to resist cell adhesion upon normal plating conditions. The cell processes of the NG108-15 cells show a preference for growth at the interface between two patterned surfaces. A factor of three increase in adhesive properties was found for the patterned surfaces over an uncoated glass surface. Design rules of a single whole cell biosensor using the NG108-15 cells can be developed based on these findings.

Effect of thermal treatments on adhesive properties of a NiCr thermal sprayed coating

Thermal sprayed coatings are most often used to resist wear or as thermal barriers. In some situations they may have to resist to the combined effects of corrosion and wear at high temperature. Ni-base thermal coatings are being used successfully in this case. It has been demonstrated that adhesion may be modified after a thermal treatment. For example, a substantial increase in adhesive properties was obtained after annealing of a chromium carbide thermal sprayed coating. Using the interfacial indentation method we have studied the influence of an annealing treatment upon adhesion of NiCr coatings for different thicknesses. It was confirmed that annealing improves adhesion to a great extent. Thermal cycling between room temperature to 900°C (×5 times) and thermal shocks consisting in heating the samples to 900°C, then quenching them in oil at room temperature (×5 times), were also studied after the annealing treatment. It was found that a beneficial effect is obtained after such treatments since the critical load necessary to initiate a crack at the interface was increased by thermal shock and even more by thermal cycling. In addition, crack propagation at the interface was slowed down after the heat treatments. This behaviour is discussed and related to the role played by the residual stresses in the coating.

Surface modification processing of synthetic rubbers by ultraviolet irradiation and sputter ion etching treatment

The mechanism by which surface modification of two kinds of synthetic rubbers (ethylene-propylene and chloroprene) was brought about by ultraviolet (UV) irradiation and sputter ion etching treatments was studied from a physicochemical point of view. The most remarkable effect of this irradiation treatment was the rapid increase in adhesion properties and the simultaneous decrease in self-stickiness. This nonsticking effect was particularly important for the rapid production of articles from thin rubber sheets. The surface modification mechanism was studied by use of SEM, ESCA, FTIR, and related interfacial analytical procedures. It was shown that surface roughening with a quite thin layer of surface oxidation (∼0.5 μm in depth) is a key factor for the development of nonsticking properties. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1625–1633, 1997

The effects of 5-bromodeoxyuridine on cyclic AMP levels and cytoskeletal organization in malignant melanoma cells

5-Bromodeoxyuridine (BUdR) causes mouse melanoma cells to develop a flattened morphology and simultaneously adhere tenaceously to the substratum on which they are growing. Experiments were done to determine if these events are coupled to increases in cAMP levels and to rearrangements in the cells' cytoskeleton. Cyclic AMP assays revealed that cell flattening and the increase in adhesive properties caused by BUdR is not accompanied by an increase in the cellular concentration of cyclic AMP. However, electron micrographs of cells grown in the presence of BUdR show a striking increase in the number of organized microtubules and microfilaments. Colchicine binding revealed no difference in the amount of tubulin present in untreated or BUdR-treated cells indicating that the increase in the number of microtubules is due to the polymerization of pre-existing tubulin subunits. These results are discussed in light of possible similar mechanisms of action of BUdR and cyclic AMP in regulating the organization of microtubules and microfilaments and the role these structures play in altering cell morphology and adhesive properties.