Preparation of High Performance Water-Soluble Quantum Dots and Their Applications in Bioassay

• Main Authors: Chin-Ping Huang, 黃靜萍
• Other Authors: Teng-Ming Chen
• Format: Others
• Language: en_US
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/70670392287297270142

博士 === 國立交通大學 === 應用化學系所 === 96 === This research focuses on the design and preparation of molecular bioindicators for semi-quantitative determination of urea, glucose, and triglycerides by using water-soluble mercaptosuccinic acid (MSA)-capped CdSe/ZnS quantum dots (QDs) (MSA-QDs). Furthermore, we have also attempted to synthesize high performance water-soluble MSA-QDs and establish a bioassay based on fluorescence resonance energy transfer (FRET) principle that was then utilized in bioassay. The fluorescence intensity of MSA-QDs, highly sensitive to the acidity/basicity of the environment, was discovered to increase with increasing basicity and a red-shifting in emission wavelength has been observed. This observation was attributed to the reduction of surface defects and modified surface structure of MSA-QDs in a basic environment that further increases the recombination probability of holes and electrons. On the contrary, a blue-shifting in emission wavelength was observed when MSA-QDs was exposed to an acidic environment and the fluorescence intensity was found to decrease with increasing acidity, which is attributed to the surface defects formation and lowering probability of electron-hole recombination. Therefore, the assay of urea and glucose has been demonstrated by monitoring the changes of basicity and acidity, respectively, when urea and glucose are hydrolyzed by urease and glucose oxidase in a series of analytes. In order to realize the feasibility of detection for lipid analytes, we have improved the fluorescence intensity and activated the surface hydrophobicity (to enhance the solubility of lipid) of MSA-QDs by carrying out photoactivation under fluorescent lamp irradiation. The assay of triglyceride has been demonstrated by monitoring the change of fluorescence intensity of MSA-QDs when triglyceride is hydrolyzed by lipase in the analytes. We have also demonstrated that a series of highly efficient, wavelength-tunable or multicolored and poly(diallyldimethylammonium chloride) QDs (PDDA-QDs) with quantum efficiency of ~48% can be synthesized through PDDA capping and photoactivation process. The most challenging task of this research is to investigate and utilize the binding affinity between tetramethylrodamine (TMR)-labeled cholic acid (CA) and self-assembled ��5-3-ketosteroid isomerase (KSI) by assuming TMR-CA as the energy donor and PDDA-QDs as the acceptor. Based on the principle of fluorescence resonance energy transfer (FRET) from TMR-CA-KSI to PDDA-QDs, our research results exhibit great potential applications in establishing effective assay systems for quantitative determination of a wide variety of biomolecules.