title: Quantifying spectral changes experienced by plasmonic nanoparticles in a cellular environment to inform biomedical nanoparticle design.
abstract: Metal nanoparticles (NPs) scatter and absorb light in precise, designable ways, making them agile candidates for a variety of biomedical applications. When NPs are introduced to a physiological environment and interact with cells, their physicochemical properties can change as proteins adsorb on their surface and they agglomerate within intracellular endosomal vesicles. Since the plasmonic properties of metal NPs are dependent on their geometry and local environment, these physicochemical changes may alter the NPs' plasmonic properties, on which applications such as plasmonic photothermal therapy and photonic gene circuits are based. Here we systematically study and quantify how metal NPs' optical spectra change upon introduction to a cellular environment in which NPs agglomerate within endosomal vesicles. Using darkfield hyperspectral imaging, we measure changes in the peak wavelength, broadening, and distribution of 100-nm spherical gold NPs' optical spectra following introduction to human breast adenocarcinoma Sk-Br-3 cells as a function of NP exposure dose and time. On a cellular level, spectra shift up to 78.6 ± 23.5 nm after 24 h of NP exposure. Importantly, spectra broaden with time, achieving a spectral width of 105.9 ± 11.7 nm at 95% of the spectrum's maximum intensity after 24 h. On an individual intracellular NP cluster (NPC) level, spectra also show significant shifting, broadening, and heterogeneity after 24 h. Cellular transmission electron microscopy (TEM) and electromagnetic simulations of NPCs support the trends in spectral changes we measured. These quantitative data can help guide the design of metal NPs introduced to cellular environments in plasmonic NP-mediated biomedical technologies.
authors.affiliation: Department of Bioengineering, Rice University, Houston, TX 77005, USA.
authors.forename: Allen L
authors.initials: AL
authors.lastname: Chen
authors.affiliation: Waitt Advanced Biophotonics Center, Salk Institute for Biological Studies, La Jolla, CA 92037, USA.
authors.forename: Ying S
authors.initials: YS
authors.lastname: Hu
authors.affiliation: Department of Bioengineering, Rice University, Houston, TX 77005, USA.
authors.forename: Meredith A
authors.initials: MA
authors.lastname: Jackson
authors.affiliation: Department of Bioengineering, Rice University, Houston, TX 77005, USA.
authors.forename: Adam Y
authors.initials: AY
authors.lastname: Lin
authors.affiliation: Department of Electrical and Computer Engineering, Rice University, Houston, TX 77005, USA.
authors.forename: Joseph K
authors.initials: JK
authors.lastname: Young
authors.affiliation: Department of Bioengineering, Rice University, Houston, TX 77005, USA.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Langsner
authors.affiliation: Department of Bioengineering, Rice University, Houston, TX 77005, USA ; Department of Electrical and Computer Engineering, Rice University, Houston, TX 77005, USA.
authors.forename: Rebekah A
authors.initials: RA
authors.lastname: Drezek
keywords: Cells; Gold nanoparticles; Hyperspectral imaging; Nano-bio interactions; Nanomedicine; Plasmon resonance; Spectral analysis