Capillary-driven Microfluidic Biosensing Platforms for Digital Biomolecule Detection
MetadataShow full item record
Microfluidic systems enable rapid diagnosis, screening, and monitoring of diseases and health conditions using small amounts of biological samples and reagents. Research on microﬂuidic devices for biological analysis has progressed sufﬁciently to be developed into fast-response, simple-to-use, portable, and reliably operating devices with the ability to detect medically relevant biological molecules that are mass manufacturable at low cost. This dissertation has been developed in five chapters and reports on the development of novel microfluidic-based biosensors for biomolecule detection considering the essential parameters for point-of-care (POC) diagnostics. POC technology permits the compilation of accurate medical information and the identification of health problems in the with-patient testing platform, allowing prompt, lifesaving treatment. In the first chapter, as an introduction to the dissertation, we are briefly discussing the basics of designing and prototyping microfluidic-based biosensors, most of which having been used or manipulated in the following chapters or our research experiments. This chapter begins with an introduction on microfluidic technology, including the hydrodynamic principles, design parameters, micro/nanofabrication methods, the common materials to be used, and the flow control systems in the microfluidics including part of our published study as a book chapter in Biomimetic Microengineering. We then discuss the immunoassay principles by introducing the common expressions and critical factors to design a successful assay. Next, we discuss different types of biosensing platforms and introduced the advantages and limitations of each platform. In the final part of this chapter, we discuss the concept of POC diagnostic, considering the healthcare demand for a real POC product and its necessity, the technical shortages of the current devices, and future perspectives for this field. The second chapter is the modified version of our publication in the journal Analyst (2018, 143, 3335-3342). In this chapter, we introduce a capillary-driven microfluidic device for microparticle-labeled immunoassay, delivering analytes and washing solutions automatically and sequentially without the need for external energy. We implemented the carbodiimide coupling method to immobilize the biomolecules on the glass substrate and quantified the target analytes by counting the surface coverage from the microparticle-labeled detector. We also introduced a new method on this simple device to measure association rate constants (Ka) to estimate the overall assay time. The sensitivity of the device was enhanced by characterizing the fluid flow and successfully demonstrated a clinically relevant limit of detection for human cardiac troponin I (hcTnI). Due to the simplicity of the proposed device, the microfluidic chip can be easily integrated with downstream biosensors for digitalizing the outcome signals. The third chapter is on utilizing an impedimetric biosensor to readout the immunoassay signals on the microfluidic chip. Considering the design parameters for impedance biosensors, we demonstrated not only high signal for microparticle-labeled immunoassay, but also sensitive enough to detect a label-free biomolecular target. Three different microparticles were tested at a fixed size to select the microparticles with optimal performance for the assay. Utilizing microparticle-labeled immunoassay for human tumor necrosis factor (TNF-α), the Limit of Detection (LOD) was improved by order of magnitude compared to the label-free bioassay. The findings of this chapter have been presented in the biomedical engineering society annual meeting (BMES 2019). The fourth chapter provides the outcome of the methodological combination of the techniques used in the second and third chapters for further miniaturization. To this end, the impedimetric biosensor was coupled with a disposable capillary-driven microfluidic to conduct a microparticle labeled immunoassay. This disposable cartridge was inserted into a hand-held impedimetric biosensor to read out the signals on one compact device to get one more step closer to POC devices. It takes about 6 minutes to run the whole assay on this integrated platform. The results of this chapter have been presented in the 23rd International Conference on Miniaturized Systems for Chemistry and Life Sciences (µTAS 2019). The last chapter is the summary of our findings within this study and discusses the limitations of the study, as well as the future developments for real, applicable POC platform addressing the life science obligations.