Microspectroscopic characterisation of gold nanorods for cancer detection

Abstract

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.