ECE Colloquium - February 12, 2014
Dr. Laura Fabris, Rutgers University, Dept. of Materials Science & Engineering
CoRE Building Lecture Hall
Gold Nanoparticles for Imaging and Sensing
Gold nanoparticles have seen a widespread growth in application because of their many useful features, such as ease of synthesis, the stability, the non-cytotoxicity, but mainly because of their intriguing optical properties. The optical properties of gold nanoparticles are characterized by the coherent oscillation of their conduction electrons at the interface between the metal and the surrounding dielectric medium, and can give rise to intense absorption bands whose position mainly depends on the shape of the nanoparticle. One of the techniquesin which gold nanoparticles have found vast application is surface enhanced Raman spectroscopty (SERS), a non-linear near field technique that takes advantage of the intense electromagnetic field enhancement that takes place in close proximity to the surface of the nanoparticle. This enhancement is particularly intense at specific locations called "hot-spots". In this talk I will present our experiments aimed at increasing the SERS enhancement by carefully tailoring the hot spots.
First of all, I will describe our results in the preparation of multifunctional gold NP dimers capable of specific cell targeting, optimized uptake, and highly resolved cel imaging that outperforms fluorescence. The systems presented here will be based on spherical NP dimers targeting U87 glioblastoma cells. Dithiolated linkers have been used to lock the NPs in a dimer conformation and also act as SERS reporters. In our experiments, thiolated PEG was used to stabilize the NP systems, while cyclic RGD peptides were employed to target avb3 integrins overexpressed on the surface of cancerous cells. Combined analysis carried out via fluorescence and Raman microscopy demonstrated the efficient SERS=based imaging of U87 cells that outperformed fluorescence.
In a second set of results, I will describe the use of gold nanostars. Gold nanostars are nanoparticles with a spherical core and very sharp spikes, who sharpness can be modulated by tuning the synthetic parameters. In this work, we have synthesized gold nanostars and deposited them on a gold substrate via a bifunctional tether, hence locking them on the surface. The sharp spikes of the nanostars act as excellent hot spots enabling the use of these substrates for SERS-based chemical sensing. We have demonstrated that this sensor is able to selectively identify both chemisorbed and physisorbed analytes down to the femtomolar regime with high selectivity and multiplexing ability.
Dr. Fabris earned her B.S./M.S. in Physical Chemistry at the University of Padova, Italy. After a one-year experience in industry she returned to graduate school to pursue her Doctorate Degree in Chemical Sciences, always at the University of Padova. Her dissertation work focused on the synthesis and characterization of peptide protected gold nanoclusters. She then took a postdoctoral position in the Department of Chemistry and Biochemistry at the University of California at Santa Barbara, where she remained until June 2009. Her work entailsed the development of surface enhanced Raman scattering (SERS)-based biosensors. In July 2009 she joined the Department of Materials Science and Engineering, where is is currently an Assistant Professor. Dr. Fabris is also a Graduate Faculty member of the Departments of Chemistry and Chemical Biology and Biomedical Engineering at Rutgers. Her research is targeting the study of plasmonic nanoparticles and their application as tags for SERS-based cell imaging and for the efficiency enhancement of plasmonic organic solar cells.