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Integration of multistep bioassays on a novel generation of capillary microfluidic devices

Boek - Dissertatie

Healthcare takes a central role in society, as it promotes general physical and mental wellbeing of people, next to contributing to a country's economy, development, and industrialization. Over the last centuries, healthcare has evolved from home remedies towards providing health services from central places like hospitals, which serve both as a treatment facilities and research centers. Nonetheless, this is not affordable nor accessible to everyone, and numerous medical challenges remain unsolved, which are different for high and low income countries (HICs and LICs). Since HICs already profit from an extensive healthcare system, there is great potential in further advancing personalized medicine (e.g. decentralized therapeutic drug monitoring), big data analyses, new scientific breakthroughs, etc. in this setting. In contrast, low income countries would profit most from solutions that mitigate their typically inadequate infrastructure, such as decentralized healthcare performed outside of labs and hospitals. In both settings there is merit in decentralized testing close to the patient in an affordable, user-friendly, robust and rapid manner, which is referred to as point-of-care (POC) testing. Overall, a good POC test should further improve quality of life for patients by enabling fast and effective treatment based on the exact disease pattern at that moment. Although a wide array of POC tests exist, ranging from simple dipstick assays to tests requiring digital readout devices (e.g. handheld or via smartphone), these are mostly available for simpler assays. Since not all diagnostics can rely on these simple tests, the number of commercially available devices for complex assays is very limited. In this context, lab-on-a-chip (LOC) technology has been introduced with the aim to perform all necessary laboratory operations for such complex assays on compact microfluidic chips. Nevertheless, despite being intensively researched for POC testing, LOC applicability in the field remains limited because of bulky ancillary equipment, and costly and complex device production. Therefore, there is a dichotomy between innovative research and limited development into commercial products. In this framework, the global aim of this thesis was to investigate and develop innovative technological solutions for a next generation of capillarity-driven microfluidic devices, and integrate complex assays on these devices for their use in POC settings. The research was divided in two research lines, each focusing on a different innovative, in-house developed technology to fabricate self-powered microfluidic devices. In the first part, binder-jetting 3D printing technology was explored as a radically new method towards the fabrication of capillarity-driven microfluidic devices for POC diagnostics in LICs. Hereto, a binder-jetting 3D printer was adapted with biocompatible powder and liquid binders to produce porous devices that derived their functionality from precise spatial control over their internal surface chemistry, creating a hydrophilic channel network in a hydrophobic support. The macroscopic characteristics of the printed material and the capillary flow therein were studied to understand fluid flow within the pore network. The capabilities of the technology were demonstrated by implementing an IgE ELISA as proof-of-concept. Hereto, the multistep assay was optimized stepwise for performance in 3D printed channels, followed by its implementation on two different devices. The first device used alkaline phosphatase signal amplification with an immobile reaction product, whereas the second device used horse radish peroxidase with a reaction product in solution, to decrease time-to-result and detection limit. Here, the technology showed promise for use as scalable, on-demand fabrication method for POC diagnostics in LICs. In the second part, the in-house developed (i)SIMPLE technology was investigated to perform complex assays, specifically adalimumab (ADM) detection for POC therapeutic drug monitoring, with two different readouts, namely fiber-optic surface plasmon resonance (FO-SPR) and colorimetric readout with a handheld reflectometer. For the former, a five-step ELISA was converted into a one-step FO-SPR immunoassay, which was then implemented for the first time on an (i)SIMPLE cartridge integrating 1:19 mixing of plasma sample with reagents and FO-SPR readout. In the second case, the five-step ELISA to detect ADM in plasma samples was downscaled in time and volume to fulfill POC requirements. This assay was then implemented on an ELISA module that executed all assay steps and incubations autonomously upon a single activation. Sample pretreatment was also further integrated by including plasma separation from whole blood in a plasmapheresis module. All these functionalities demonstrated the capability of (i)SIMPLE technology to perform complex multistep assays upon a single activation, including sample pretreatment steps and different readout strategies, thereby effectively showing its applicability towards POC testing.
Jaar van publicatie:2022
Toegankelijkheid:Open