IntroductionCoagulation pathway changes play an important role in the outcome of both clot propagation and fibrinolysis. The structurefunction relationship of the developing fibrin clot is known to be affected by many factors, such as environment, therapy, and disease, compared with normal clot growth. 1,2 A fibrin clot's primary microstructure consists of a disordered network of entangled, branching fibrin fibers. Thinner fibers are associated with networks that display an increased number of branch points, creating denser, less permeable clots that have a known association with thromboembolic disease. [3][4][5][6] More open/permeable networks are formed from thicker fibers, the latter displaying a reduced number of branch points for a given amount of fibrinogen and producing a more porous system. [7][8][9][10] Clots with altered fibrin microstructure exhibit different susceptibility to fibrinolysis, 8,10,11 with clot permeability being the rate-limiting factor for the activity of the fibrin network degradation enzyme plasmin. The permeability will aid or hamper the ability of tissue plasmin activator, tPA, and/or urokinase plasmin activator to move through the 3-dimensional fibrin network and activate the zymogen plasminogen to fibrinolytic plasmin. The effect of anticoagulants such as heparin in the therapeutic manipulation of fibrin clot microstructure by thrombin inhibition increases clot permeability/porosity and produces clots with thicker fibers. 12,13 The evolution of clot microstructure is associated with significant changes in blood viscoelasticity (a measure of a material's viscous and elastic properties). Viscoelastic properties are among the most sensitive measures of fibrin polymerization and blood clot structure. 7,14 In the present study, we focused on the formation of the incipient clot, which provides the microstructural template that determines the future clot morphology, 15-17 by measuring the incipient clot's viscoelastic properties with an oscillatory shear technique known as Fourier transform mechanical spectroscopy (FTMS). [18][19][20] This technique provides an accurate determination of the gel point (GP) of coagulating blood and allows the microstructure of the incipient clot to be quantified by fractal analysis, a technique widely used in medicine and biology to characterize nonlinear growth in branching network structures. 21 The authors of previous studies of clot structure on the basis of techniques such as scanning electron microscopy have reported qualitative descriptions of clot microstructure (involving terms such as "rigid clot structures," "open/porous/dense/loose," etc 1 ), whereas studies of the fractal properties of fibrin gels on the basis of light-scattering techniques have been restricted to dilute solutions of fibrinogen, at concentrations less than those of physiologic relevance in whole blood. 22 A recent study of fibrin clot structure suggests there is a definitive diagnostic potential of characterizing clot structure and the modulation of clot architecture as a pos...

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Implantable ventricular assist devices (VADs) have proven efficient in advanced heart failure patients as a bridge-to-transplant or destination therapy. However, VAD usage often leads to infection, bleeding, and thrombosis, side effects attributable to the damage to blood cells and plasma proteins. Measuring hemolysis alone does not provide sufficient information to understand total blood damage, and research exploring the impact of currently available pumps on a wider range of blood cell types and plasma proteins such as von Willebrand factor (vWF) is required to further our understanding of safer pump design. The extracorporeal CentriMag (Thoratec Corporation, Pleasanton, CA, USA) has a hemolysis profile within published standards of normalized index of hemolysis levels of less than 0.01 g/100 L at 100 mm Hg but the effect on leukocytes, vWF multimers, and platelets is unknown. Here, the CentriMag was tested using bovine blood (n = 15) under constant hemodynamic conditions in comparison with a static control for total blood cell counts, hemolysis, leukocyte death, vWF multimers, microparticles, platelet activation, and apoptosis. The CentriMag decreased the levels of healthy leukocytes (P < 0.006), induced leukocyte microparticles (P < 10−5), and the level of high molecular weight of vWF multimers was significantly reduced in the CentriMag (P < 10−5) all compared with the static treatment after 6 h in vitro testing. Despite the leukocyte damage, microparticle formation, and cleavage of vWF multimers, these results show that the CentriMag is a hemocompatible pump which could be used as a standard in blood damage assays to inform the design of new implantable blood pumps.

The host- and bacteria-derived extracellular polysaccharide coating of the lung is a considerable challenge in chronic respiratory disease and is a powerful barrier to effective drug delivery. A low molecular weight 12-15-mer alginate oligosaccharide (OligoG CF-5/20), derived from plant biopolymers, was shown to modulate the polyanionic components of this coating. Molecular modeling and Fourier transform infrared spectroscopy demonstrated binding between OligoG CF-5/20 and respiratory mucins. Ex vivo studies showed binding induced alterations in mucin surface charge and porosity of the three-dimensional mucin networks in cystic fibrosis (CF) sputum. Human studies showed that OligoG CF-5/20 is safe for inhalation in CF patients with effective lung deposition and modifies the viscoelasticity of CF-sputum. OligoG CF-5/20 is the first inhaled polymer therapy, represents a novel mechanism of action and therapeutic approach for the treatment of chronic respiratory disease, and is currently in Phase IIb clinical trials for the treatment of CF.

BackgroundStroke is the second largest cause of death worldwide. Hypercoagulability is a key feature in ischaemic stroke due to the development of an abnormally dense clot structure but techniques assessing the mechanics and quality of clot microstructure have limited clinical use. We have previously validated a new haemorheological technique using three parameters to reflect clot microstructure (Fractal Dimension (df)) ex-vivo, real-time clot formation time (TGP) and blood clot strength (elasticity at the gel point (G’GP)). We aimed to evaluate these novel clotting biomarkers in ischaemic stroke and changes of clot structure following therapeutic intervention.MethodsIn a prospective cohort study clot microstructure was compared in ischaemic stroke patients and a control group of healthy volunteers. Further assessment took place at 2–4 hours and at 24 hours after therapeutic intervention in the stroke group to assess the effects of thrombolysis and anti-platelet therapy.Results75 patients (mean age 72.8 years [SD 13.1]; 47 male, 28 female) with ischaemic stroke were recruited. Of the 75 patients, 32 were thrombolysed with t-PA and 43 were loaded with 300 mg aspirin. The following parameters were significantly different between patients with stroke and the 74 healthy subjects: df (1.760 ± .053 versus 1.735 ± 0.048, p = 0.003), TGP (208 ± 67 versus 231 ± 75, p = 0.05), G’GP (0.056 ± 0.017 versus 0.045 ± 0.014, p < 0.0001) and fibrinogen (3.7 ± 0.8 versus 3.2 ± 0.5, p < 0.00001). There was a significant decrease in df (p = 0.02), G’GP (p = 0.01) and fibrinogen (p = 0.01) following the administration of aspirin and for df (p = 0.003) and fibrinogen (p < 0.001) following thrombolysis as compared to baseline values.ConclusionPatients with ischaemic stroke have denser and stronger clot structure as detected by df and G’GP. The effect of thrombolysis on clot microstructure (df) was more prominent than antiplatelet therapy. Further work is needed to assess the clinical and therapeutic implications of these novel biomarkers.