Nanotopography of PS/PMMA Polymer Demixed Surfaces for Dynamic Platelet Assay Applications

Abstract

Platelets are small but critical constituents of blood; whose role is to promote coagulation and form clots that stop bleeding after damage to blood vessels. The protein von Willebrand Factor (vWF) facilitates the attachment of platelets to the site of injury by binding to exposed collagen in the vessel wall and its availability and function are essential. Conditions such as von Willebrand Disease (vWD) affect 1 in 100 people and occurs when vWF function is compromised. Unfortunately, many who have the condition are unaware of the associated bleeding risk and so there is a need for diagnostic tests that reflect the in vivo physiology of vWF-platelet interactions. A recent advancement in this regard, has been the development of a Dynamic Platelet Function Assay (DPFA) by the Royal College of Surgeons in Ireland (RSCI). This device comprises a simple microfluidic flow chamber in which a surface doped with immobilised vWF is used to challenge fluorescently labelled platelets in whole blood perfused over it at arterial shear rates (1500 s-1). However, as this surface uses endogenous vWF it does not truly represent the in vivo circumstances. Hence, the research presented here addresses refinement of the properties of a synthetic surface that can directly entrap vWF from flowing blood in a way that supports the requirement for it to uncoil under adequate shear force to make available platelet sites. Results obtained demonstrate how substrates designed show positive platelet interaction across all blood groups and dynamic analysis shows similar values for polymer surfaces in comparison to the endogenous surface. That created with +750 PS microspheres/ml in air has been shown to produce the highest platelet coverage (40.20 ± 13.30%) and is found to have a topography comprising nanoscale features (height: ±130 nm, FWHM <1 μm). Consequently, understanding of autologous vWF/platelet interactions on synthetic surfaces has been significantly advanced by this work and moves DPFA testing closer to a simple and accurate diagnosis of vWD and related blood disorders.

Date of Award	Jul 2020
Original language	English
Supervisor	Brian Meenan (Supervisor) & Adrian Boyd (Supervisor)