Increased bioassay sensitivity of bioactive molecule discovery using metal-enhanced bioluminescence
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We report the use of bioluminescence signal enhancement via proximity to deposited silver nanoparticles for bioactive compound discovery. This approach employs a whole-cell bioreporter harboring a plasmid-borne fusion of a specific promoter incorporated with a bioluminescence reporter gene. The silver deposition process was first optimized to provide optimal nanoparticle size in the reaction time dependence with fluorescein. The use of silver deposition of 350 nm particles enabled the doubling of the bioluminescent signal amplitude by the bacterial bioreporter when compared to an untouched non-silver-deposited microtiter plate surface. This recording is carried out in the less optimal but necessary far-field distance. SEM micrographs provided a visualization of the proximity of the bioreporter to the silver nanoparticles. The electromagnetic field distributions around the nanoparticles were simulated using Finite Difference Time Domain, further suggesting a re-excitation of non-chemically excited bioluminescence in addition to metal-enhanced bioluminescence. The possibility of an antiseptic silver effect caused by such a close proximity was eliminated disregarded by the dynamic growth curves of the bioreporter strains as seen using viability staining. As a highly attractive biotechnology tool, this silver deposition technique, coupled with whole-cell sensing, enables increased bioluminescence sensitivity, making it especially useful for cases in which reporter luminescence signals are very weak.
KeywordsMetal-enhanced fluorescence Plasmons Surface-enhanced fluorescence Bioluminescence Bioreporters Bioactive molecules Nanobiotechnology
This work was supported by the Singapore National Research Foundation under the CREATE program: Nanomaterials for Energy and Water Management; a Levi Eshkol scholarship from the Israeli Ministry of Science and Technology and Shimona Geresh award. The authors also thank the IUI, Eilat, Israel, for the use of its facilities, and Dr. Evgeni Eltzov, Dr. Maya Shnit-Orlande, and Nahshon Siboni for sample collection, technical support, and guidance.
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