Enhanced Surface Plasmon Resonance Sensors Based On Self-assembled Layers And Au Nanoparticles

Surface plasmon resonance (SPR) technology has become an important method for biomolecular interaction analysis because of its unique advantages. Biosensors based on SPR technology have been widely used in various fields such as biology, medicine and chemistry. Unfortunately, the inability of conventional SPR to measure extremely small changes in refractive index hinders its application in sensitive detection of small molecules. To address this drawback, new approaches by combining the self-assembly technique and Au nanoparticles (AuNPs) with home-built SPR were developed for sensitive detection of small molecules. In brief, this thesis includes the following three parts:1. A glucose-selective surface plasmon resonance sensor based on self-assembled multilayersA glucose-selective surface plasmon resonance sensor was constructed by using of biospecific interaction between concanavalin A (Con A) and sugars. The sensing element was self-assembled multilayers of Con A and dextran formed on Au film. At the presence of glucose, the self-assembled multilayers were disintegrated. As a result, the surface plasmon resonance signal was changed obviously. The signal changes were correlative to the concentrations of glucose. The results showed that this sensor could detect the glucose selectively in the range of 0.1 ~ 50 mmol/L, and the sensing element could be regenerated for several times. The preparation of the self-assembled multilayers was simple and the Con A built into the multilayers retained its binding activity to sugar. Furthermore, similar principle could be used to construct other new small molecules SPR sensors.2. A signal enhanced surface plasmon resonance sensor based on dextran / Con A-labeled AuNPs self-assembled multilayersBased on the research of the first part, the dextran / Con A-labeled AuNPs self-assembled multilayers were built on Au film through biospecific interaction. The Con A-labeled AuNPs (Con A-AuNPs) were prepared by AuNPs labeling technology. When placed in glucose solution, the self-assembled layers were disintegrated, and result in changes of SPR signal. Hence, the concentrations of glucose could be determined. The results showed that the detection limit of glucose was reduce by 1 order of magnitude due to the coupling of plasmon wave between AuNPs and Au films. Here, The detection limit of glucose was 0.01 mmol/L.3. A signal enhanced surface plasmon resonance sensor based on Con A / dextran- modified AuNPs self-assembled bilayerProtein-labeled AuNPs were exceedingly dependent on the ionic strength and pH of the surrounding medium, while the chemical modified AuNPs were stable in a wide range of salt concentrations and pH values. Therefore, dextran-modified AuNPs (dextran-AuNPs) were successfully prepared through AuNPs reacted with 16-mercaptohexadecanoic acid (16-MHDA), 2-(2-aminoethoxy) ethanol, epicholorhydrin and dextran respectively. Then the Con A / dextran-AuNPs self-assembled bilayer was built on Au film by means of biospecific molecular recognition. At the presence of glucose, the self-assembled bilayer was disintegrated and the surface plasmon resonance signal changed. Hence, the glucose concentrations were detected. The results showed that the dextran-AuNPs had good stability and was effective for enhancing the signal changes. Furthermore, through preparation of other AuNPs complex as SPR sensing element, similar principle could be used to construct SPR sensors for other small molecules.