Fibre-based microfluidics for point-of-care diagnostic applications

Abstract

This research project focuses on the development of fibre-based microfluidic devices for point-of-care (POC) detection in developing countries. Since paper and textile (the two most common fibre-based materials) have great potential for diagnostic applications, it has been of interest to researchers to combine traditional paper/textile strip tests with microfluidic devices to make them more sensitive, specific and user-friendly, while keeping them low-cost. These devices were originally designed for colorimetric detection. However, their sensitivity and functionality are not comparable with conventional laboratory tests and concentrated effort is required to improve them. This is the aim of this study. This thesis makes four original contributions to the functionality of recently- developed fibre-based microfluidic devices for use in real-world applications. The initial work presented in this thesis aims to enhance the sensitivity of the colorimetric detection methods currently in use with paper/textile strip tests by developing an alternative method of measuring the length of stained segments rather than their colour intensity. The length measurement method allows users to interpret results using a ruler, independent of image processing software. The following study considers the newly-developed fibre-based blood typing sensors. Although these sensors have shown promising performance for normal ABO blood types, correct typing of ABO sub-groups, which have a weak haemagglutination reaction with blood typing antibodies, is difficult to achieve. This is because the red blood cell (RBC) transport mechanism in fibre is not fully understood. This section focuses on understanding the underlying principles and the effects of fibre properties in blood typing sensors, and the results will enable sensor designers to further optimize low-cost blood typing sensors for detecting all types of blood. The subsequent section demonstrates an extremely simple and low-cost method for separating blood plasma from samples of whole human blood on paper-based sensors. Blood is the main body fluid which correlates with the condition of the body and is commonly used for biomedical diagnostics. However, due to the strong red colour, it is not suited for colorimetric detection and the plasma needs to be separated from RBCs before bio-diagnostics. Therefore, strategies to separate plasma from RBCs can enhance the functionality of paper-based sensors. This section focuses on integrating the blood plasma separation and colorimetric detection into a single device. This method paves the way for widespread biomedical tests using whole blood samples on paper-based microfluidic devices. The final part explores the ability of fibre to transport nutrients to cells in vitro. Although a three-dimensional (3D) cell culture in vitro is used to simulate the actual physiological environment, it relies on stacking individual layers and providing sufficient nutrients for cell growth. This study proposes the use of hydrophilic thread to support a multilayer cell culture system developed by stacking layers of scaffold. With the help of the thread, the cells are able to proliferate over a period of time. By expanding low-cost methods for further development of fibre-based microfluidics, this work gives researchers/sensor designers the ability to design more functional sensors for use in resource- limited regions.