Development of microfluidics platform for biological and biochemical applications

Abstract

Biological and biochemical assays are the essential core in the biomedical research and clinical diagnosis. Microtiter plate technologies are commonly adopted, and require multiple laborious steps, such as liquid transfer, reagent mixing, and washing. Therefore, labor-intensive work is required to carry out the assays. Moreover, efforts to decrease the cost for each assay have been made by decreasing the dimension of the well compartments. However, evaporation problems become significant when the working volume becomes small, so does the problem in inaccurate pipetting. Therefore, new technological advancements for biological and biochemical studies are critical.

Microfluidics enables the manipulation of tiny volume of fluid within microchannels. The microchannel does not only lower the cost for an assay, it also enhances the speed of reaction by the high surface-area-to-volume ratio. Furthermore, size-controlled droplet emulsions can be produced within microchannels. These droplets, usually in the volume of nanoliter to picoliter, can function as compartments similar to the microwells. These droplets can be interrogated at a rate of hundreds to thousands of droplets per second. The high throughput and low volume consumption characteristics establish droplet microfluidics as an emerging technique to address current limitations in the development of assays.

In this thesis, we focus on the integration and development of current microfluidic techniques for biological and biochemical applications. We identify some of the current techniques and integrated them into a platform, and characterized the sensitivity and accuracy of the platform. Moreover, we developed a high-speed program to characterize the fluorescence readout from the droplets, with logic to decide whether the droplet is of importance for downstream analysis. All the modules combine to form a powerful toolbox for biological applications.

By using the detection and analysis modules, we perform a diagnosis on an inflammatory marker that consumes ten-fold-less in reagents, and with a ten-fold increase in sensitivity. Also, our wash-free approach can eliminate the laborious work in conventional methods.

By using the detection module, the program, the reagent addition and sorting module, we can selectively crosslink hydrogels based on the contents within. This approach can solve the fundamental problem that arises from the random process during encapsulation steps. With majority of the droplets being empty, tedious work in downstream are required. Therefore, our platform can eliminate the downstream laborious work by addressing the fundamental problem in droplet microfluidics.

The ability to detect, inject, and sort droplets based on their fluorescence intensities can help understanding the fundamental problems in biology and biochemistry. As an example of future applications, our platform enables the detection of single cancer cell with high sensitivity. The cell can be sorted for further analysis, such as investigating the mutation and drug resistance with a well-developed sequencer. In addition, our platform can perform a high throughput screening on aptamers based on their catalytic activities, thus identifying new aptamers for enzymatic reactions. Therefore, the platform is well-equipped with powerful modules for addressing current limitations, and can also contribute to the development of novel approaches in biological and biochemical applications.