"Ultraplasmonic Fluorescent Supraparticles for Diagnostic Applications" 

Gabriel Aguirre Cruz, MSE PhD Candidate 

Advisor: Professor Lia Stanciu

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ABSTRACT

Plasmonic-enhanced fluorescence has emerged as an exciting avenue within the realm of diagnostics, primarily due to its heightened sensitivity capabilities. Particularly noteworthy are the anisotropic plasmonic particles, which exhibit exceptionally robust resonances within their electric fields at the tips. When these particles are combined with an organic fluorophore and meticulously separated by a precisely defined spacer, the resultant effect is an extraordinarily intense fluorescent phenomenon. Within the scope of our research, we have conceptualized a novel system comprised of a polymeric supraparticle measuring 500 ± 10nm, designed to resonate harmoniously with spherical Au-based plasmonics ranging from 50-10nm in length. This supraparticle system was designed in three different coverage density configurations in respect of plasmonics to core beads. This with the purpose of studying the effect of fluorescence enhancement with different densities of plasmonics on core bead. Our supraparticle system exhibits potential to be a colorimetric/enhanced-fluorescence platform for diagnostics in clinical settings. To validate the practical applicability of these fluorescent labels in the realm of diagnostics, we functionalized our fluorescent core-shell particles with aptamer sequences and subjected them to binding analysis for bacterial targets, specifically the oral pathogens E. Faecalis and P. Gingivalis. TEM microscopy confirmed the selective high-affinity binding of our plasmonic labels to whole-cell bacterial targets, exhibiting high coverage along the surface proteins of bacteria. Additionally, to assess the application of our labels we have also trialed use of the plasmonic labels in a paper-based lateral-flow-assay (LFA) platform. A preliminary assay using model protein streptavidin has shown the colorimetric limit of detection of detection for these labels to be in the nanogram range, while we expect to obtain significantly lower values when the enhanced fluorescent modality is applied.