Pathologic fibrin formation and cold-induced clotting of membrane oxygenators during cardiopulmonary bypass

In 1,800 patients undergoing cardiac surgery over a 2-year period, 11 incidents of abnormal inlet pressure elevations occurred before the membrane oxygenators. In 3 patients, the oxygenators had to be changed during cardiopulmonary bypass. This complication was found to be caused by fibrin formation possibly secondary to precipitation of fibrinogen with other coagulation factors in the heat exchangers of the oxygenators during the cooling phase. Large amounts of fibrin were demonstrated in the heat exchanger of the oxygenators. After careful washing of the apparatus, plasmin was added and fibrin was detected by measuring D-dimer levels. In heat exchangers from uneventful operations, only trace amounts of fibrin were found. Because there were no cold agglutinins demonstrated in the patients before surgery, cryoprecipitation studies were performed soon after surgery. When the patients' plasma samples were studied at different temperatures, from 37 degrees C down to 3 degrees C, cryoprecipitates or a gel (in 1 patient only) were formed. This indicated that there might be something abnormal with regard to fibrinogen-fibrin formation. The study patients were therefore investigated after the acute phase of the operation had ended for various coagulation factors, as well as for fibrin gel network characteristics. The results were compared with those of a control group (n = 10) with uneventful operations. There were no differences between the groups with regard to levels of coagulation factors VII and VIII and von Willebrand factor, although they were increased in both groups. The mean levels of coagulation inhibitors, antithrombin and Protein S, were slightly lower in the study patients. All of these patients had a highly pathologic, ie, tight fibrin gel network, except for the patient in whose sample a gel formed, despite being treated with aspirin or oral anticoagulants. The network was also tighter in some of the controls (v middle-aged reference individuals), although it was significantly tighter in the patients. It is concluded that some individuals who have an increased tendency to form tighter fibrin gel networks might be at increased risk for a severe complication during cardiac surgery performed under hypothermia.     

Effect of zinc ions on fibrin network structure

In addition to calcium, other physiologically important divalent cations (magnesium and zinc) are known to influence fibrin formation and structure. We have studied the effect of different concentrations (0-20 micromol/l) of zinc ions (Zn2+) in the absence and presence of calcium on the gel structure formed in purified fibrinogen-enzyme systems. For that purpose, we used turbidity measurement, liquid permeation and confocal three-dimensional microscopy of the gel as well as sodium dodecyl sulphate (SDS)-gel electrophoresis. The results of turbidity measurements indicated that the clotting time decreased with increasing concentrations of Zn2+. The fiber mass: length ratio (mu) values showed that the porosity of the gels increased in a concentration-dependent manner, i.e. at higher concentrations of Zn2+, larger pores with thicker fibrin fibers were formed. Three-dimensional microscopy data of the gels were in good agreement with the mu data. On SDS-gel electrophores of reduced fibrin, no cross-linking was observed in the presence of zinc ions only (without the addition of calcium ions), nor were D-D dimer bands observed in non-reduced plasmin digested fibrin samples in the presence of zinc ions only. The above results show that zinc changes the fibrin gel structure and that this effect appears to be independent of calcium.     

Textile-based microfluidics: modulated wetting,mixing, sorting,and energy harvesting

Microfluidics technology allows us to perform rapid and massively parallel manipulation and characterization of fluid samples with biomedical and environmental importance. In the attempt to achieve resource-efficient fabrication and operation of the microfluidic devices, paper-based and thread-based microfluidics have been previously demonstrated by other researchers. We propose to develop textile-based microfluidics, formed by three-dimensional networks of individual threads, to further advance the ability of paper-based and thread-based microfluidics. This paper describes four different phenomena that we investigate in textile-based microfluidic systems: modulated wetting, liquid mixing, liquid sorting, and energy harvesting. Our results indicate the feasibility of textiles as a new platform to develop low-cost microfluidic technology.     

Fibrin in human plasma: gel architectures governed by rate and nature of fibrinogen activation

The porosity, fiber dimension and architecture of fibrin gels formed in recalcified plasma on addition of thrombin are, within a certain range of thrombin concentrations, determined by the initial rate of fibrinogen activation. Furthermore, the initial network formed in this range creates the scaffold into which subsequently activated fibrinogen molecules are deposited. Change in thrombin concentration that occurs during gelation, as a result of indigenous thrombin generation in plasma, does not qualitatively alter this scaffold. The formation of the networks obeys a more complex rule when low amounts of thrombin are added or with recalcified plasma without added thrombin. These networks are tighter than would be expected from the initial rate of fibrinogen activation. In this case an extremely porous network is probably formed initially, followed by formation of a secondary, superimposed network of a less porous architectural quality. The latter structure appears to be governed by the rate of indigenous generation in plasma of thrombin-like enzymes in combination with the particular type of fibrinmonomers being produced. In addition our findings establish the rules for proper determination of gel structures in clinical plasma samples. The sequelae of a variety of clot structures that may be formed in vivo are discussed.     

Synthesis of α-alumina powder with internal nanostructures from Al13-cluster

Nanostructured α-alumina powder was synthesized by precipitation and calcination of Al₁₃-clusters that were formed by the hydrolysis of Al³⁺ions with hydroxide. The Al₁₃-clusters were precipitated with oxalic acid by two-stage and one-stage precipitation techniques. The precipitates were calcined in air at 1100 °C. The resulting α-alumina particles were characterized using particle size analyzer, X-ray diffraction (XRD) and transmission electron microscope (TEM). The pH and precipitation technique were found to influence the microstructural features of the α-alumina powder produced. Alumina with more extensive nanostructures inside the grain can be produced through the two-stage precipitation technique.     

Thermal behavior of extruded and injection‐molded poly(lactic acid)–talc engineered biocomposites: Effects of material design,thermal history,and shear stresses during melt processing

Reinforced biocomposites were compounded by the reactive extrusion of poly(lactic acid) (PLA) and chemically modified microlamellar talcs. Talc was functionalized by the hydrolysis and condensation reaction of its surface hydroxyl groups with different kinds of organosilanes, namely, 3‐aminopropyl triethoxysilane and (3‐glycidoxypropyl)trimethoxysilane, and commercially available tri‐isocyanates, namely, Bayhydur 3100 and Desmodur 3900, which feature hydrophilic and hydrophobic behaviors, respectively. PLA–talc biocomposites were also compounded by the addition of two types of reactive biodegradable compatibilizing agents, namely, maleic anhydride and glycidyl methacrylate modified PLA. The resulting compounds were melt‐processed by injection molding to get flat substrates with different formulations. The thermal responses of the extruded compounds and injection‐molded items, specifically the first and second thermal transitions, were analyzed by differential scanning calorimetry. In particular, the influence of the different material formulations, their thermal history, and/or shear stress in single‐ or multiple‐stage heating and/or melt processing on the glass transition, crystallinity, and melting behavior of the biocomposites was investigated. The experimental findings revealed that the macroscopic thermal response of the compounds (i.e., extruded pellets) and substrates (i.e., injection‐molded flat slabs) manufactured by the melt processing of the available formulations was controlled and significantly improved by the fine‐tuning of the chemical (i.e., reaction mechanisms, chemical bonds) and physical interactions (i.e., steric hindrances, physical bonds) among the modified talc, PLA, and compatibilizing agents. These results are of great practical importance and open up broader scenarios for the industrial application of biopolymers and biocomposites, specifically in all of those consumer goods where thermal stability and the preservation of mechanical performance at moderate and high temperatures of the materials are pivotal. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45179.     

Purification of peroxidase isoenzymes from turnip roots

Simple reproducible procedures for purification of the main soluble (S) and ionically bound (IB) cationic peroxidase isoenzymes from turnip roots were established. The procedures included ammonium sulfate precipitation of the isoenzymes, chromatographic separation of the main isoenzymes using cellulose phosphate columns and purification to homogeneity by hydrophobic interaction chromatography on phenyl Sepharose columns. The specific activity of the phenyl Sepharose purified S and IB isoenzymes were 2760 and 896 units/mg protein with 140 and 4.8 fold increase over the crude extract and 38 and 13% recovery. The pH maxima and K(m) for phenol and H2O2 of purified S and IB were determined.     

Antimicrobial activity of cotton fabrics containing immobilized enzymes

Immobilization of α‐amylase, alkaline pectinase, and laccase enzymes onto ester‐crosslinked as well as Cu‐chelated cotton fabrics were carried out. Factors affecting the extent of enzyme‐loading and retention activities of immobilized enzymes were studied. Proper conditions for attaining higher extent of fixation along with better retained activity were studied. The degree of antimicrobial activity of treated fabric samples against gram‐negative and gram‐positive bacteria, filamentous, and nonfilamentous fungi were evaluated. The antimicrobial activity is determined by the type of substrate, i.e., Cu‐chelated > ester‐crosslinked and activated cotton substrate, and the nature of immobilized enzyme, i.e., alkaline pectinase > α‐amylase > laccase, irrespective of the used microorganism. The antimicrobial activities of the treated fabrics are completely maintained after laundering at least ten consecutive wash cycles. Further consecutive wash cycles, i.e., 20 or 30 cycles, has practically negative impact on the retained antimicrobial efficacy. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1754–1761, 2007     

INHIBITION OF ACIDIC AND PITTING CORROSION OF NICKEL USING NATURAL BLACK CUMIN OIL

The inhibition effect of natural black cumin oil on the corrosion of nickel in 0.1 M HCl solution was studied using galvanostatic and potentiodyanmic anodic polarization techniques. It was found that the inhibition efficiency increased with an increase in the inhibitor concentration of this oil. The inhibitive action of black cumin oil was attributed to the adsorption on metal surface. The adsorbed layer acts as a barrier between the metal surface and aggressive solution, leading to a decrease in the corrosion rate. The adsorption process follows the Langmuir adsorption isotherm. It was found also that black cumin oil provides good protection to nickel against pitting corrosion in sodium chloride solutions.