Real-time analysis of blood coagulation and fibrinolysis : new rheological and optical sensing techniques for diagnosis of haemostatic disorders.

• The haemostatic system has a dual paradoxical function in the body. It should arrest bleeding whenever needed, but also keep the blood flowing in the circulatory system without any obstructing blood clots. The system is complex with maoy intertwined processes that interact to produce a fine-tuned regulation of the performance. In case of malfunction in this regulation there may be an excessive coagulation ability, thrombophilia, or bleeding tendency, haemophilia. These are common disorders in the Western societies and may be lethal. The long-term airo of this work is therefore to improve the laboratory diagnosis of haemostatic disorders, for thrombophilia in particular. To achieve this goal a global approach has been chosen, meaning that the environment in which a blood sample is analysed should mimic the physiology of the haemostatic system to better elucidate the overall situation in a particular individual. A first attempt to assess the susceptibility for tissue plasminogen activator induced lysis and coagulum structure in plasma as markers for deep vein thrombosis showed promising results with 47% abnormals among the DVT patients included in the study. To improve this assay new sensing techniques were needed, since one of the most important conditions included in a global assay is analysis of whole blood, i.e. blood with all types of blood cells present. Whole blood is opaque and excludes the traditional optical methods that have been used for coagulation analysis. Several candidate techniques have been identified and surface plasmon resonance (SPR), quartz crystal microbalance-dissipation (QCM-D), and free oscillation rheometry (FOR) have been evaluated for haemostatic studies in this thesis. SPR is an optical surface sensitive technique that has showed promising results for measurements in blood plasma during coagulation and fibrinolysis and for whole blood coagulation. The SPR responses were sensitive to treatments with heparin and oral anticoagulants, which are substances used to treat thrombosis. QCM-D that is sensitive to mass deposition and viscoelastic changes in the sample at the quartz crystal surface has been tested in combination with SPR and provided new information about the viscoelastic properties of the coagulum, although with similar sensing depth as SPR. The idea of combined sensing techniques was reconsidered and resulted in a combination of SPR and FOR for siroultaneous real-time measurements in a blood sample. FOR is bulk sensitive and probes rheological changes in the sample. The combination was applied in studies of plasma and whole blood coagulation as well as plasma fibrinolysis. Coagulation studies including chemical surface modifications by using thiol-based self-assembled monolayers were also attempted. Finally, the FOR/SPR combination was found to be sensitive to inhibition of platelet aggregation and blood cell shape changes iroplying that studies on the cellular component of the blood is possible. In conclusion, the combination of FOR and SPR is a promising sensing system for an improved global assay for haemostatic disorders.

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MEDICIN

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