4 May 2009 Detection of immunocomplex formation by enhanced photoluminescence of antibody-functionalized diatom biosilica
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Diatoms are single-celled photosynthetic algae that make silica shells or "frustules" with intricate features patterned at the nano and microscales. In this study, antibody-functionalized diatom biosilica frustules serve as a biosensor platform for selective and label free antibody-antigen immunocomplex formation by enhanced photoluminescence. Biosilica frustules of 10 micron diameter were isolated from cells of the centric marine diatom Cyclotella sp. They were then mounted on glass and covalently functionalized with the model antibody Rabbit Immunoglobulin G (IgG) to yield a uniform nanostructured surface that selectively binds to its complimentary antigen, Goat anti-Rabbit IgG. Diatom frustules possess an intrinsic capacity to emit blue light when excited with a UV laser light source, a property called photoluminescence. Binding the antibody-functionalized diatom frustule with its complimentary antigen selectively enhanced the intrinsic photoluminescence intensity of the diatom frustule by a factor of three, whereas challenging the antibody-functionalized diatom frustule with a non-complimentary antigen, Goat anti-human IgG did not change the intrinsic photoluminescence intensity. The nucleophilic immunocomplex increases the photoluminescence by donating electrons to non-radiative sites on the photoluminescent diatom biosilica, thereby decreasing non-radiative electron decay and increasing radiative emission. The intensified photoluminescence intensity is correlated to the antigen, goat anti-rabbit IgG concentration, with a binding constant of 2.8 ± 0.7x10-7 M.
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Debra K. Gale, Timothy Gutu, Jun Jiao, Chih-Hung Chang, Gregory L. Rorrer, "Detection of immunocomplex formation by enhanced photoluminescence of antibody-functionalized diatom biosilica", Proc. SPIE 7321, Bio-Inspired/Biomimetic Sensor Technologies and Applications, 732104 (4 May 2009); doi: 10.1117/12.819153; https://doi.org/10.1117/12.819153

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