UC San Diego

As the microfluidic technology has been attracted more attentions and has potential for wide range of applications, in our research work we are utilizing this technique to expand its capability in different aspects of study. In this dissertation, I am going to present two topics of the work: Molecular interaction study using microfluidic techniques and Microfluidic droplet-based applications on single-cell analysis.Biosensors are powerful analytical tools for many applications including drug discovery, medical diagnostics, and environment monitoring. Because of the advance of microfluidic technology, biosensors have a significant improvement by merging the biosensor into lab-on-chip (LOC) technology. In most of the microfluidic sensor, the detection mechanism is through the reaction event that occurs when the flowing analyte in the channel physically or chemically react with the immobilized reactant. The immobilization of recognition elements is needed prior to the sample detection, but this can be a disadvantage of using microfluidic device due to one-time use only. To address this issue, we develop a new readout technique, “Transient Induced Molecular Electronic Signal (TIMES)”. The measured signal from TIMES is directly coming from the induced charge generated from the analyte or chemical reaction, and no immobilization of reactant on electrode surface is needed. I am going to present the work on protein-ligand study based on our microfluidic TIMES measurements, which is a highly potential study in drug discovery research area. Besides, TIMES technique has potential to be an alternative readout for lateral flow assay (LFA) study. The recent work we have done with paper-based TIMES study for antibodies binding interaction will be presented. In the second topic, I am going to show our development on microfluidic device that used for single-cell analysis. There are two main workflows to perform single cell analysis: 1.) Plate-based method and 2.) Droplet-based method. The plate-based method is the traditional way, it is costly and time consuming. While in second method, the cells are encapsulated into small droplet, and all the reaction can be done in this tiny droplet, having capability to operate more than 10,000 cells in one reaction, so it saves more use of reagent and time on operation. In our study, we are trying to identify specific cell subtype by using enhancer screening with droplet-based analysis. However, the droplet manipulation is needed in this procedure. To be specific, droplet merging and double emulsion formation are two main steps in droplet-based analysis. Droplet merging is achieved for reagent addition after cells are lysed and RNA is released in the droplet. In our work, we developed a new microfluidic platform to merge droplets by using pillar-induced mechanism. The double emulsion is another main technique for droplet-based analysis. The main purpose for double emulsion formation is to make droplets compatible to water phase so the targeted droplets can be sorted with FACS equipment. In our study, we are going to expand its application on relating cell morphology to gene expression. The double emulsion technique is applied with image-guided sorting system that developed in our lab and combined with gene sequencing will provide value information for cell genotype-phenotype analysis.