Low-cost polymer chip for isothermal amplication assay

Abstract

There is an increasing need to optimize diagnostics and health care and to develop methods to deliver the care closer to the patient’s homes, in order to reduce the load on hospitals and clinics. In developing countries it is a challenge to obtain effective diagnosis and treatment for outbreaks of infectious diseases, such as influenza and tuberculosis, where the latter is causing more deaths than any other infectious disease. Point-of-care systems based on microfluidic devices have the potential to fulfill some of these needs and new technologies based on DNA amplification are continuously emerging and are under implementation on such devices. For these technologies to be competitive, devices need to be fabricated through lowcost mass-production processes, e.g. by injection moulding. In academia, though, often the fabrication methods are not compatible with industrial mass-production and this can present a significant barrier to the commercialization of developed devices. It is therefore vital to seek a manufacturing process applying industry-level technologies for rapid prototyping of microfluidic devices. The research presented in this thesis focused on three main topics: First, a microfluidic system was designed that used capillary structures to ensure controlled filling of separate, but connected, fluidic chambers. The filled liquids needed to remain stable under heating to the temperature required for the assay below. Second, microfluidic chips were fabricated using either injection moulding with shims defined by micromilling combined with ultrasonic welding to seal the chips or by using laser ablation combined with adhesive bonding. The fabricated chips were characterized and the burst pressure of so-called phaseguide structures was studied systematically. At the end of the project, the design of functional prototype chips developed using laser ablation was transferred to a mass-production fabrication process by injection moulding. Third, an integrated lab-on-a-chip system implementing isothermal rolling circle amplification of synthetic influenza and tuberculosis nucleic acid targets on the chip platform was developed and demonstrated. The assay was run in an automated setup in which magnetic microbeads were used to transport the target between the different assay steps and the amplification products were detected using an optomagnetic readout. Several assay strategies were investigated and quantitative dose-response curves were measured. The results demonstrated the feasibility of performing the complete three-step assay in a low-cost mass-producible multi-chamber device in an automated manner with results that were comparable to those obtained in comparable laboratory assays.