Development of paper-based lateral flow blood coagulation assays: activated partial thromboplastin time (aPTT)
The analysis of blood-clotting time is necessary for a range of clinical applications such as evaluating coagulation disorders and controlling the impact of different anticoagulant drug therapies. Coagulation disorders cause extreme blood-loss, resulting in extensive morbidity and mortality, especially in resource-poor environments. Furthermore, death rates related to coagulopathy are elevated in poor countries due to the expensive in terms of instruments and personnel and due to a lack of suitable blood coagulation tests that allow rapid diagnosis and treatment. In addition, there is a need for diagnostics that facilitate point-of-care use. Lateral flow devices represent a type of device that can achieve this as well as be used in emergencies, enabling the exclusion of coagulopathies, preventing unnecessary hospital admissions, and decreasing the burden on healthcare resources. Paper-based devices are showing suitable technology for applications in low-resource environments due to their low cost, speed, and sustainability. The focus of this thesis is to develop a paper-based lateral flow blood coagulation device based on the activated partial thromboplastin time (aPTT). The approach taken was to use Whatman qualitative chromatography paper and wax printing to fabricate the device. In addition, reagent and test sample volumes were optimised and then used to evaluate the viscosity influences of a paper-based coagulation aPTT device on the fluid flow rate. Furthermore, optimisation of aPTT and calcium chloride (0.025 M) reagents were performed and tested in normal and abnormal plasma. The results demonstrate that a two-stage assay is useful for determining blood-clotting properties through time and distance, though the impact was not significant. Though the outcomes were positive, they need to be significant, so it is essential to consider where to deposit reagents and the distribution of reagents on the strip. In addition, to make a significant influence, several approaches need to be performed to maximise the effect, such as a single-stage assay.