Silver nanoparticles (AgNPs) have the potential to increase the quantum yield and decrease the excitation lifetime of bound fluorophores because of their unique properties. These effects alleviate fluorophore degradation, a current limitation of spectroscopic viability for fluorescence markers, by increasing resistance to photobleaching while simultaneously increasing emission detectability with metal-enhanced fluorescence (MEF). The utility of silver nanoparticles is increased by functionalization of fluorophores in conjunction with targeting and stabilizing agents, which enable target localization and nanovehicle viability under biological conditions.

We are investigating conditions to synthesize and stabilize solutions of colloidal AgNPs of 20 nm diameter by sodium borohydride reduction with citrate-capping agents for enhanced shelf stability. We explore mechanisms for the attachment of mNeonGreen proteins containing silver-bonding peptide tags to AgNPs, measuring the success of functionalization with methods including fluorimetry, dynamic light scattering (DLS), and UV-Vis spectroscopy.

Methods explored for the purification of functionalized AgNPs include centrifugation, passive dialysis filtration, and gel electrophoresis in order to optimize methodology for the extraction of pure, monodisperse nanoparticles. Viability of functionalized particles over time was determined for varying parameters such as the concentrations of protein, functional groups of buffers, and ionic strength of solution. Biological simulation was performed using buffered solution around biological pH containing NaCl. Shelf stability was tested using varying temperature conditions.

Our goal is to develop a method for the functionalization of stable AgNPs coated with fluorescent proteins that prove to have sustained viability in ionic environments around biological pH. Successfully functionalized AgNPs with fluorescent and targeting capabilities can be used in biomedical imaging with localization specificity. Using MEF with silver we seek to increase fluorophore detectability and minimize photobleaching in order to enhance the practical effectiveness of biomarkers.

Mathew Tantama

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