Caitlin Richmond - Hinds Community College-Utica Campus
Co-Author(s): Hongtao Yu, Jackson State University, MS
Gold nanoparticles (AuNP) are known to be able to either quench or enhance the fluorescence of certain dyes, and are widely used in bio-imaging, sensing, and detection. These dyes are called fluorophores, and when a particular wavelength of light excites their molecules they fluoresce. The interaction between AuNP and fluorophores may be linked to the molecular construct of the dye. This study aims to explore the role of specific functional groups when in relation to one fluorophore and its fluorescence behavior when in the presence of AuNP. As a result, we tested the hypothesis that functional groups affect the quenching behavior of indole dye. Indole, a great fluorophore, is the base structure for a larger amount of important compounds found naturally and is known for its pharmaceutical uses. Indole’s derivatives all differ in the attachment of different functional groups to the base structure. Therefore, indole and its derivatives are chosen to explore fluorescence affected by functional groups when quenched by AuNP. Indole is used as the control or baseline to compare the other derivatives with connected functional groups. In this study the derivatives used where tryptamine (amine group), tryptophan (carboxyl & amine group), indole-3-lactic acid (carboxyl & hydroxyl group), 3-(3-hydroxypropyl)-1H-indole (hydroxyl group) and 3-indolepropionic acid (carboxyl group). Spherical AuNP (15 nm) was synthesized by reducing 10 mM HAuCl4 using 1% trisodium citrate. The prepared AuNP in water (1×10-4 µM) was titrated into the aqueous solution of the indole (10 µM). Static fluorescence quenching was observed between the AuNP and indole dye. Stern Volmer plots show that indole fluorescence was quenched the most, while fluorescence of tryptophan that included an amine and carboxyl functional group was quenched the least. In conclusion, fluorescence quenching of indoles by AuNP is influenced by the functional groups attached to the fluorophores. Future studies include studying whether functional groups affect the fluorescence quenching of other dyes by AuNP and in what ways they affect them to support the hypothesis.
References: 1. Kaushik, N. K., Kaushik, N., Attri, P., Kumar, N., Kim, C. H., Verma, A. K., & Choi, E. H. (2013). Biomedical importance of indoles. Molecules, 18(6), 6620-6662.
2. Rai, U. S., Yu, H., Anjaneyulu, Y., Dubey, M., & Ray, P. C. (2008). Gold nanoparticle based surface enhanced fluorescence for detection of organophosphorus agents. Chemical physics letters, 460(1), 187-190.
Funder Acknowledgement(s): I would like to thank Hua Deng for assisting me in the lab and overseeing my experiments. I am very gracious to Hongtao Yu for allowing me to work in his lab and use his materials and equipment along with helping in critiquing my presentation as a whole. I also would like to thank Jackson State University and their REU program that allowed me the opportunity to carry out this research on their campus. And many thanks to National Science Foundation (NSF1461143) for financial support.
Faculty Advisor: Hongtao Yu, Noel Gardner, email@example.com
Role: I performed all experimentation and research under the instruction of Hongtao Yu and Hua Deng.