| Surface plasmon resonance (SPR) is a sensitive optical technique for measuring the thickness and structure of ultrathin adsorbate layers, based on the metal film/solution interfacial refractive index change. The attractive features of SPR in monitoring biomolecular interactions include the high sensitivity, label-free and real-time measurements, relatively simple procedure, and low sample consumption. Furthermore, SPR measurements have the ability to provide more information about analyte concentration determination, binding affinity, kinetic analysis of the biomolecular interactions. SPR spectroscopy has become a widely used technique to study molecular interactions such as antibody-antigen, DNA-DNA, DNA-protein, protein-protein, receptor-ligand and peptide-and protein-membrane interactions. High throughput SPR sensors (multiple samples assayed with a single chip) broaden the applications of the technique. In view of SPR advantages, we investigated the medical diagnosis applications of SPR in significant diseases, such as Alzheimer’s Disease (AD), cancer, and so on.1. SPR techinique is surface-sensitive, which is easily affected by experiment conditions, such as thickness of metal film, surface cleaning, chip preparation, molecular immobilization, and so on. First, the effects of the technique conditions were systematically investigated, including the preparation and application of different chips, the immobilization of molecule, the kinetics analysis. The study is necessary for the following SPR application.2. SPR has been used to simultaneously quantify β-amyloid (Aβ) peptides Aβ(1-40) and Aβ(1-42) present in CSF samples. By immobilizing capture antibodies specific to the two peptides in separate fluidic channels, signal amplification was implemented in the detection of Aβ level. The concentrations as low as20pM can be readily measured. The range of Aβ peptide concentrations measurable by this method spans four orders of magnitude. The ability of regenerating the sensor surface for repeated measurements not only improves the reproducibility, but also enhances the sample throughput. Our data reveal that the ratio of Aβ(1-40)concentration versus Aβ(1-42) concentration in CSF samples from AD patients is almost twice as high as that from healthy persons. In contrast to the commonly used enzyme-linked immunosorbent assay (ELISA), SPR obviates the need of a more expensive and less stable enzyme conjugate and the use of carcinogenic substrate for the signal detection, and allows the binding events to be monitored in real time. The investigation demonstrates that SPR can potentially serve as a viable alternative for facile and sensitive clinical analyses of important biomarkers related to neurodegenerative diseases.3. The interaction of tumor suppressor p53with apo-metallothionein (apo-MT) has been carried out using SPR techinique. MT was first tethered onto the carboxymethylated dextran film. Via incorporation of Glycine-HCl (pH2), the open structure of apo-MT was formed. The binding constant of1.4×108M-1suggests the strong interaction of wild-type p53with apo-MT. The specific binding of p53to consensus double stranded DNA was hindered after metal chelation from p53by apo-MT. Furthermore, inhibition of the interaction between p53and apo-MT imposed by p53/DNA complex was observed. Thus, SPR could potentially serves as an attractive technique for monitoring p53conformational change and transcriptional activity regulated by the MT/apo-MT couple. |
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