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UBC Theses and Dissertations

Silica based immunoassays for a covalently attached antigen Melzak, Kathryn


An immunoassay was developed using a monoclonal antibody and anantigen covalently immobilized on silica, showing that silica is a potentially useful assay substrate. Silica beads prepared from tetraethyl orthosilicate (0.78 pmdiameter) and fused quartz slides were thoroughly cleaned and modified with 3-aminopropyltriethoxysilane. Amine groups on the modified slides and beads were used for carbodiimide mediated coupling to carboxyl groups on a peptide antigen. High surface concentrations of antigen were achieved. Antibody binding to the antigen-modified beads and slides was measured using an iodinated monoclonal antibody. The equilibrium constant for the antibody binding on the beads was ten times higher than on the flat silica, but the maximum amount bound was lower. Immunoassays performed using a second enzyme-labelled antibody to detect the monoclonal antibody bound to the silica permitted detection of the antigen at 10-8 M using the modified beads and at10-7 M using the slides.

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