Development of novel microfluidic systems for the establishment of highly sensitive protein-based optical biosensors and self-powered POC DNA analysis system
Date of Issue2016-07-08
School of Mechanical and Aerospace Engineering
Over last few decades, human being have been suffered from various infectious diseases. Lab-on-chip (LOC) technologies have played great role in revolutionizing the way in vitro medical diagnostics are done and provide easy to use, cost-effective miniaturized systems with faster analysis time, which can be used for near-patient or Point-Of-Care (POC) tests. The POC technology enables effective prevention and early detection of diseases and it helps to drastically deplete the mortality. Therefore, in this dissertation, I focused on the development of POC protein and nucleic acid biomarkers-based infectious disease diagnostic systems. Proteins and nucleic acids (DNA and RNA) are mostly used as biomarkers to identify the specific infectious diseases. The single specific biomarker in body fluids is, however, not sufficient to be used in clinical setting for the detection due to their low-concentration (few pg/ml). Unlike nucleic acid biomarkers, the amplification of protein biomarkers would be impracticable itself. Therefore, I have developed the Rotationally Focused Flow (RFF) method to enhance the sensitivity of protein biomarker based biosensor. The RFF was made by adding a less dense fluid, ethanol, to focus the target fluid near the sensor surface in a simple T-shape microchannel, which results in reducing the distance between target molecules and immobilized probe molecules. The focusing rate of target fluid can be controlled by changing volumetric fraction ratio between two fluids. I verified the formation of the RFF in the T-shaped microchannels using both computational fluid dynamics simulations and flow experiments with fluorescent beads. The sensitivity enhancement using RFF method was investigated with label-free silicon microring resonator sensor using the biotin-streptavidin interaction as a model system. Remarkably, the sensitivity of microring sensor with the RFF method was increased by 8-order of magnitudes compared to the single flow method where only target fluid was injected to the microchannel. I conducted a series of experiments and utilized these data to verify the sensitivity enhancement in the RFF method and to rule out other potential contribution factors including denaturation of target molecules. The investigation clearly showed that the RFF method is a simple and effective way to enhance the sensitivity of label-free optical sensor and can be widely applied to any biosensor without requiring additional instruments. Microfluidic lab-on-chip (LOC) system is the most suitable platform for the satisfaction of POC diagnostic system requirements. Fluidic pumps and valves are among the key active components for LOC system, however, they often require on-line electrical power or battery and make the whole system bulky and complex, therefore limit its application in POC testing. In order to solve the problem, I have developed two types of self-powered actuators with corresponded valves. First self-powered actuator & valve is a disposable switchgear controllable vacuum actuator which is made of two disposable syringes, poly (methyl methacrylate) switchgear and O-ring. In the vacuum actuator, an opened syringe and a blocked syringe are bound together and act as a working syringe and an actuating syringe, respectively. The negative pressure in the opened syringe is generated by restoring force of the compressed air inside a blocked syringe and utilized as the vacuum source. A Venus symbol shape of switchgear provides multi-function including reagent reservoir, push-button for the vacuum actuator, and on-off valve. Using the vacuum actuator, I have developed a self-powered switch-controlled nucleic acid extraction system (SSNES) for the establishment of disposable and equipment-free sample preparation device of POC diagnostic system. The SSNES consists of three sets of vacuum actuators, switchgears and microfluidic components. The SSNES can be widely used as self-powered and disposable system for DNA extraction and the syringe based vacuum actuator would be easily utilized for diverse applications with various microchannels as a self-powered fluidic pump. Second self-powered actuator & valve is that a hydration reaction based self-powered actuator. The working principle of the actuator is that hydrogen gas is generated by hydration reaction of powder with water and expanded to push in reagents through reaction zone toward the outlet of microchannel. The gas flow can be controlled with attaching a cover tape to or detaching a cover tape from the holes (inlets and outlets) of microchannels. In addition, I also have developed and integrated exothermic reaction based non-instrumented RPA device which performs the amplification of DNA with self-powered heating. Based on the developments, I present the development of a non-instrumented DNA analysis system (NIDAS) that enable to carry out total analysis of DNA biomarkers from sample to answer within 1 hour.
DRNTU::Engineering::Mechanical engineering::Fluid mechanics