Characterization and Development of Lateral Flow Assays for Automated Multi-step Processes and Point-of-care Cervical Cancer Detection
thesisposted on 08.05.2020, 03:55 by Emilie I Newsham
Paper-fluidic devices are a popular platform for point-of-care diagnostics due to their low cost, ease of use, and equipment-free detection of target molecules. The most common example is the lateral flow assay, in which samples are added to a paper membrane and a colorimetric indicator provides a binary signal indicating whether the molecule of interest is present. A novel lateral flow assay was developed to detect a protein biomarker for early stage cervical cancer. Cervical cancer can be cured if detected and treated at an early stage, but approximately 90% of cervical cancer deaths occur in low and middle-income countries due to lack of accessible testing. Methods for detecting the biomarker, valosin-containing protein (VCP), were optimized using enzymatic and gold nanoparticle dot blots, then lateral flow assays were developed and validated using purified VCP and cervical cancer HeLa cells. Future validation with patient tissue samples will permit translation of this device to testing clinics in low-resource areas. Despite advantages for use in resource limited settings, lateral flow assays are limited by their inability to perform more complex or multi-step processes, such as nucleic acid amplification or enzymatic signal enhancement. Thermally actuated wax valves are one mechanism that provides complete control over fluid obstruction and release. To better understand how wax valves can be used in fully automated, self-contained lateral flow assays, different sizes and geometries of valves were tested to investigate their effects on actuation time, flow rate, and flow pattern. Another limitation in the understanding of lateral flow assays is the lack of experimental data describing the microscale flow within the pores of the paper membrane that drives the biophysical reactions in the assay. Mathematical models can be designed to explain macroscopic phenomena, but so far, no literature has compared microfluidic models to microfluidic data. To quantify microfluidic properties within lateral flow assays, fluorescent nanoparticles were imaged flowing through different areas of the membrane and their velocity was quantified using micro-particle image velocimetry (µPIV). Scanning electron microscope images were used to verify that this experimental model was reasonable for describing microfluidic properties of the lateral flow assay. Altogether, this document investigates how developing lateral flow assays for cervical cancer detection can save lives by improving the accessibility of an early diagnosis, and how more robust lateral flow assay characterization can expand their applicability to a broad range of detection processes.