NANOFLUIDIC SINGLE MOLECULE DETECTION (SMD) FOR PROTEIN DETECTION AND INTERACTION DYNAMICS STUDY
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The objective of this work is to develop a micro/nanofluidic-based single molecule detection (SMD) scheme, which would allow us to inspect individual protein or protein complex study protein-protein interactions and their dynamics. This is a collaboration work with MD Anderson Cancer Center and we applied this scheme to study functions of various proteins related to cancer progression in hope to shed new light on cancer research. State-of-the-art micro/nano-fabrication technology is used to provide fused silica micro/nano-fluidic channel devices as our detection platform. Standard contact photolithography, projection photolithography and advanced electron-beam lithography are used to fabricate micro/nano-fluidic channel with width ranging from 100nm to 2?m. The dimensions of these miniaturized biochips are designed to ensure single molecule resolution during detection and shrinking the detection volume leads to increase in signal-to-noise ratio, which is very critical for SMD. To minimize surface adsorption of protein, a fused silica channel surface coating procedure is also developed and significantly improved the detection efficiency. A fluorescent-labeled protein sample solution is filled in the fluidic channel by capillary force, and proteins are electro-kinetically driven through the fluidic channel with external voltage source. Commercial functionalized Quantum Dots (Qdots) are used as fluorescent labels due to its various advantages over conventional organic dyes for single molecule multi-color detection application. A fluorescence correlation spectrometer system, equipped with a 375nm diode laser, 60x water immersion objective with N.A. of 1.2 and two avalanche photodiodes (APD) is implemented to excite single molecules as well as collect emitted fluorescence signals. A two-dimensional photon burst analysis technique (photon counts vs. burst width) is developed to analyze individual single molecule events. We are able to identify target protein or protein complex directly from cell lysate based on fluorescence photon counts, as well as study the dynamics of protein-protein interactions. More importantly, with this technique we are also able to assess interactions between three proteins, which cannot be done with current ensemble measurement techniques. In summary, the technique described in this work has the advantages of high sensitivity, short processing time (2-3 minutes), very small sample consumption and high resolution quantitative analysis. It could potentially revolutionize the area of protein interaction research and provides us with more clues for the future of cancer diagnostics and treatments.
Jing, Nan (2009). NANOFLUIDIC SINGLE MOLECULE DETECTION (SMD) FOR PROTEIN DETECTION AND INTERACTION DYNAMICS STUDY. Doctoral dissertation, Texas A&M University. Available electronically from