title: Effects of unidirectional flow shear stresses on the formation, fractal microstructure and rigidity of incipient whole blood clots and fibrin gels.
abstract: Incipient clot formation in whole blood and fibrin gels was studied by the rheometric techniques of controlled stress parallel superposition (CSPS) and small amplitude oscillatory shear (SAOS). The effects of unidirectional shear stress on incipient clot microstructure, formation kinetics and elasticity are reported in terms of the fractal dimension (df) of the fibrin network, the gel network formation time (TGP) and the shear elastic modulus, respectively. The results of this first haemorheological application of CSPS reveal the marked sensitivity of incipient clot microstructure to physiologically relevant levels of shear stress, these being an order of magnitude lower than have previously been studied by SAOS. CSPS tests revealed that exposure of forming clots to increasing levels of shear stress produces a corresponding elevation in df, consistent with the formation of tighter, more compact clot microstructures under unidirectional flow. A corresponding increase in shear elasticity was recorded. The scaling relationship established between shear elasticity and df for fibrin clots and whole blood confirms the fibrin network as the dominant microstructural component of the incipient clot in terms of its response to imposed stress. Supplementary studies of fibrin clot formation by rheometry and microscopy revealed the substantial additional network mass required to increase df and provide evidence to support the hypothesis that microstructural changes in blood clotted under unidirectional shear may be attributed to flow enhanced thrombin generation and activation. CSPS also identified a threshold value of unidirectional shear stress above which no incipient clot formation could be detected. CSPS was shown to be a valuable haemorheological tool for the study of the effects of physiological and pathological levels of shear on clot properties.
authors.affiliation: College of Engineering, Swansea University, Swansea, UK.
authors.forename: N
authors.initials: N
authors.lastname: Badiei
authors.affiliation: College of Engineering, Swansea University, Swansea, UK.|College of Medicine, Swansea University, Swansea, UK.
authors.forename: A M
authors.initials: AM
authors.lastname: Sowedan
authors.affiliation: College of Engineering, Swansea University, Swansea, UK.
authors.forename: D J
authors.initials: DJ
authors.lastname: Curtis
authors.affiliation: College of Engineering, Swansea University, Swansea, UK.
authors.forename: M R
authors.initials: MR
authors.lastname: Brown
authors.affiliation: College of Medicine, Swansea University, Swansea, UK.|NISCHR Clinical Haemostasis and Biomarker Research Unit, ABMU NHS Trust Hospital, Morriston, Swansea, UK.
authors.forename: M J
authors.initials: MJ
authors.lastname: Lawrence
authors.affiliation: College of Engineering, Swansea University, Swansea, UK.
authors.forename: A I
authors.initials: AI
authors.lastname: Campbell
authors.affiliation: College of Medicine, Swansea University, Swansea, UK.|NISCHR Clinical Haemostasis and Biomarker Research Unit, ABMU NHS Trust Hospital, Morriston, Swansea, UK.
authors.forename: A
authors.initials: A
authors.lastname: Sabra
authors.affiliation: College of Medicine, Swansea University, Swansea, UK.|NISCHR Clinical Haemostasis and Biomarker Research Unit, ABMU NHS Trust Hospital, Morriston, Swansea, UK.
authors.forename: P A
authors.initials: PA
authors.lastname: Evans
authors.affiliation: Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: J W
authors.initials: JW
authors.lastname: Weisel
authors.affiliation: Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: I N
authors.initials: IN
authors.lastname: Chernysh
authors.affiliation: Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: C
authors.initials: C
authors.lastname: Nagaswami
authors.affiliation: College of Engineering, Swansea University, Swansea, UK.
authors.forename: P R
authors.initials: PR
authors.lastname: Williams
authors.affiliation: College of Medicine, Swansea University, Swansea, UK.|NISCHR Clinical Haemostasis and Biomarker Research Unit, ABMU NHS Trust Hospital, Morriston, Swansea, UK.
authors.forename: K
authors.initials: K
authors.lastname: Hawkins
mesh_terms: D001777:Blood Coagulation / Q000187:drug effects*; D017709:Fractals; D005782:Gels; D013314:Stress, Mechanical
chemical_list: D005782:Gels
keywords: Gel point; clotting time; controlled stress parallel superposition; fractal dimension; shear stress