Development of droplet-based microfluidic sensor for wash-free biological assay

Abstract

Over the past several decades, many technologies and resources have greatly impacted on biological research. Among them, droplet-based microfluidic chips for biological assays can reduce costs and consumption of reagents and samples, cuts the time spent on experiments, and increases sample throughput. It also increases accuracy, reliability, and sensitivity of experiments. Consequently, microfluidics is considered to be a romising technology for biological studies, allowing generation of high throughput, robust and portable platforms. The advantages of droplet-based microfluidics have led to many innovative technologies in optical analysis. The analytical detection techniques for droplets play critical roles in the development and application of droplet-based microfluidic systems. To analyze droplet content quantitatively, the surface-enhanced Raman scattering (SERS) detection technique provides a promising potential for high sensitive detection in droplet system. According to WHO's report, hepatitis B virus (HBV) infection remains a major public health threat, with more than 350 million humans worldwidely infected. Carriers of HBV not only become long-term reservoirs of virus but also eventually develop chronic liver disease. Although excellent vaccines exist, there are no effective therapies for chronic HBV infections. Early and timely detection of disease biomarkers can prevent the spread of infectious diseases, and drastically decrease the death rate of people suffering from them. However, most of these conventional tests used for biomarker detection are complicated,take hours for completion, consume large volumes of samples and reagents, and require bulky and expensive instruments. Therefore, simple, low cost and portable diagnostic devices are absolutely needed. Hence, there have been significant advances in the development of microfluidic platforms for the biomarker detection of diseases. In this thesis, we designed and fabricated a highly accurate and reproducible SERS-based microdroplet sensor for the rapid detection of sequence-specific DNA by combining the advantage of SERS and droplet based microfluidics. Quantitative analysis was performed by measuring the SERS peak areas, and the LOD for the sequence-specific target DNA was estimated to be 0.1 pM. The droplet-based microfluidic sensor for wash-free DNA assay shows a potential applicability for high-throughput detection of sequence-specific DNA.