Raman and Fluorescence Spectral Imaging of Live Breast Cancer Cells Incubated with PEGylated Gold Nanorods

Abstract

The optical properties of PEGylated gold nanorods (PEG-GNR) in interaction with cells have been investigated with Raman and fluorescence microspectroscopic imaging. The emission spectra were compared with those from dispersions of GNR, which can be characterized by a broad emission bandwidth of approximately 60 nm with a band maximum around 675 nm. These properties are in good agreement with observations from various other gold substrates and (nano)particles. The emission spectra from cells incubated with PEG-GNR were dominated by Raman scattering from locations where no GNR were present. Intense fluorescence spectral lines, with peak amplitude comparable with the Raman scattering from cells, were observed from locations containing GNR. The frequency range of the fluorescence emission spectra coincided mainly with the Raman fingerprint region from 500 cm−1 to 1800 cm−1, excited by the laser emission line at 647.1 nm. No surface-enhanced Raman spectra were observed. It was furthermore observed from cluster analysis of the Raman and fluorescence hyperspectral datasets that the GNR-related integrated fluorescence emission band from an individual cell could be sub-divided in multiple bands with slightly varying band maxima. Raman difference spectra of cells with GNR minus control cells showed that the amplitude of lipid signal in cells incubated with PEG-GNR was increased. An excellent correlation was found between the increased lipid signals and locations of the nanorods. This positive correlation between Raman signals from lipids and fluorescence signals from gold nanorods supports that gold nanorods are locally accumulating in lipid vesicles within the cells.

Classifying Raman spectra of extracellular vesicles based on convolutional neural networks for prostate cancer detection

“…We obtained the Raman signal of EVs using a home‐built confocal Raman microscope . This provides Raman measurements and optical trapping.…”

Correlative SEM SERS for quantitative analysis of dimer nanoparticles

“…27 The spectra contain the SERS signal and some fluorescence, which originates from the fluorescence enhanced signal from the R6g molecules and from the gold nanoparticles. 28 The SERS signal was isolated using a filter with a smoother function specifically designed to separate background fluorescence and Raman spectra. 29 A pretreated Fig.…”

Microspectroscopic characterisation of gold nanorods for cancer detection

“…Because of the small photon momenta involved, the interband transitions were assumed to be direct. In the last decade luminescence from gold structures has been investigated extensively, 147,154,[163][164][165][166][167][168][169][170] and direct radiative electron-hole recombination as proposed by Mooradian is still considered the main emission mechanism.…”

“…44,78,81,144 Here, we PEGylated all but one GNR sample, in the manner previously described. 81,170 In biomedical applications, PEG-GNR are directed to the cell surface using antibodies. Part of the PEG-GNR samples were conjugated with HER81 monoclonal antibody (Immunicon, Huntingdon Valley, PA, USA) using a bifunctional PEG crosslinker orthopyridyl dithio-polyethylene glycol-succinimidylpropionate (OPSS-PEG-PDP, Polypure, Oslo, Norway).…”

“…Previously, we observed that GNR in SK-BR-3 cells can be identified by their fluorescence emission (Chapter 4). 170 It was shown that the shape of this GNR characteristic fluorescence emission changes for nanorods at different locations in the cells. The spatial information from the cluster image (Figures 6.6D and 6.6F) and the BSE images (Figures 6.6B and 6.6C) suggests a co-localization of broadband fluorescence and carbon related Raman responses with the gold nanoparticles.…”