Graduate Thesis Or Dissertation
 

Biomolecule detection by amplified photoluminescence of germanium doped diatom biosilica

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/05741w23g

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  • There is significant interest in the fabrication of nano- and micro-structured silica with spatially ordered features, which exhibit enhanced optoelectronic properties with application to the next generation of display devices, semiconductors, and sensors. Currents methods of fabrication employ top down processes which use extremes of temperature, pressure, and power. There is an emergence of interest in bio-fabrication techniques, specifically diatoms. Diatoms are single celled photosynthetic algae that make silica shells called frustules. In this study, diatom frustule biosilica acts as a label-free, photoluminescence based, reporter of immunocomplex formation and is metabolically doped with germanium (Ge) to amplify the intrinsic baseline photoluminescence signal. Diatom frustules covalently functionalized with the Rabbit IgG antibody report immunocomplex formation with the antigen anti-Rabbit IgG by at least a three times enhancement in the photoluminescence signal intensity at a surface site density of approximately 4000 IgG molecules μm⁻². Immunocomplex formation on the frustule surface follows a Langmuir isotherm with a binding constant of 2.8 ± 0.7 x 10⁻⁷ M, which is within the range of binding constants for other conventional detection methods. Diatom frustule biosilica metabolically doped with up to 0.4 weight % Ge by a two stage photobioreactor cultivation strategy exhibits amplified photoluminescence upon annealing in air up to 400°C. X-ray photoelectron spectroscopy shows that germanium dioxide (GeO₂) metabolically doped in the frustule biosilica is thermally converted to germanium oxide (GeO) which exhibits an amplified photoluminescent signal by up to four times. Additionally, Raman spectroscopy mapping demonstrates that the Ge can be metabolically targeted to a specific sub-micron location in the diatom frustule. Ge doped diatom biosilica reports biomolecule detection by a more intense photoluminescence signal intensity by a factor of 10 over the native biosilica without Ge. This study demonstrates that Ge doped silica structures with nano- and micro-spatially ordered features can be biologically fabricated to exhibit enhanced photoluminescence properties for future sensor and display applications.
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