Microspectroscopic Characterisation of Gold Nanorods for Cancer Cell Detection

Gold nanoparticles have a long history in the biomedical applications. Recently in particular gold nanorods (GNR) have attracted attention. From a biocompatability point of view as well as from an optical angle, GNR are promising contrast enhancing agents in tumour detection. However, before GNR can be applied in the clinic, their safety will have to be assessed and approved. Throughout this thesis, we have used mainly Raman microspectroscopy to characterise GNR as well as their interactions with breast cancer cells. First, the Raman response of unperturbed ductal breast carcinoma cells was determined. Then, the interaction of GNR with SK-BR-3 cancer cells has been investigated using both Raman imaging for live cell imaging and scanning electron microscopy on fixated cell samples. Raman mapping of SK-BR-3 cells incubated with GNR revealed that the optical response of intracellular GNR differs from the response of GNR in solution. Moreover, the spectral distribution of GNR emission from within the cells appeared to be spatially non-uniform. The fluorescence-like emission profiles from GNR were further discussed by comparing their absorption and emission characteristics to literature values. In addition, live Raman cell mapping showed a coincidence of the GNR signature with that of increased lipid signals, which indicated local accumulation of GNR within intracellular lipid vesicles. To increase the signal specificity of the GNR, Raman markers can be incorporated into the GNR coating. Therefore, we investigated the adsorption of the near-infrared dye indocyanine green to GNR-like surfaces. By extending the existing Raman microspectroscopic imaging system with a 3D modality, cells were analysed into greater detail. Both the resolution of the confocal system and the nature of the samples determined the optimal imaging conditions. Initial measurements performed on fixated SK-BR-3 allowed the assignment and localization of intracellular components with depth resolution. Within GNR-incubated SK-BR-3, GNR fluorescence was detected at several intracellular locations. However, while previously GNR were solely detected in colocalisation with pronounced lipid signals, in 3D imaging GNR were depicted close to the nuclei as well. In order to obtain more conclusive data, we suggested several improvements for the 3D Raman imaging system

Monomer adsorption of indocyanine green to gold nanoparticles

NIR-dye encoded gold nanoparticles (GNP) are rapidly emerging as contrast agents in many bio-imaging/sensing applications. The coding process is usually carried out without control or a clear understanding of the metal–liquid interface properties which, in contrast, are critical in determining the type and extension of dye–metal interaction. In this paper, we investigated the effect of gold surface composition on the adsorption of indocyanine green (ICG) on GNP, simulating the surface conditions of gold nanorods on citrate-capped gold nanospheres. These substrates allowed a careful control of the metal–liquid interface composition and, thus, detailed absorption and fluorescence concentration studies of the effects of each individual chemical in the colloidal solution (i.e.bromide anions, cetyl trimethylammonium ions and Ag+ ions) on the ICG–gold interaction. This study reveals the drastic effect that these experimental parameters can have on the ICG adsorption on GNP

Monomer adsorption of indocyanine green to gold nanoparticles

NIR-dye encoded gold nanoparticles (GNP) are rapidly emerging as contrast agents in many bio-imaging/sensing applications. The coding process is usually carried out without control or a clear understanding of the metal-liquid interface properties which, in contrast, are critical in determining the type and extension of dye-metal interaction. In this paper, we investigated the effect of gold surface composition on the adsorption of indocyanine green (ICG) on GNP, simulating the surface conditions of gold nanorods on citrate-capped gold nanospheres. These substrates allowed a careful control of the metal-liquid interface composition and, thus, detailed absorption and fluorescence concentration studies of the effects of each individual chemical in the colloidal solution (i.e. bromide anions, cetyl trimethylammonium ions and Ag+ ions) on the ICG-gold interaction. This study reveals the drastic effect that these experimental parameters can have on the ICG adsorption on GNP. © 2011 The Royal Society of Chemistry.Supported by the COST Action MP0603 (Micro CARS) through a short term scientific mission (L.G.) and by the SenterNovem IOP Photonic Devices project PRESMITT (IPD067771).Peer Reviewe

A comparison of breast cancer tumor cells with varying expression of the Her2/neu receptor by Raman microspectroscopic imaging

The Her2/neu proto-oncogene is amplified in 25 to 30 percent of human primary breast carcinomas. The roles of Her2/neu have been reported before in literature, showing different relations to intracellular lipid composition. Here, we use Raman microspectroscopic imaging to reveal the chemical composition of single live cells from breast carcinoma cell lines MDA-MB-231, MDA-MB-435s and SK-BR-3, which express Her2/neu receptor in different extent. Average Raman spectra of the different cell populations show prominent lipid presence in all cell lines. With high significance, Raman difference spectra reveal increased lipid contents, as well as a lower degree of fatty acid saturation in the MDA-MB cell lines with respect to the SK-BR-3 cells. These results are confirmed by hierarchical cluster analysis of single cells. High internal consistency of the chemical compositions in the cell lines is shown by hierarchical cluster analysis on a single matrix composed of the data of different cells from a single cell line. Although Her2/neu expression is highest for SK-BR-3 cells, their lipid contents are lower than that of the MDA-MB cell lines, which express less to no Her2/neu receptors. Rather than metabolic rate or senescence, the degree of metastaticity of the cells appears to be related to the polyunsaturated fatty acid contents of the cells