Raman mapping and hyperspectral data analysis : a study of in vitro cellular response to titanium dioxide and goethite nanoparticles

Reports that new engineered nanomaterials may cause adverse health effects calls for more systematic studies and development of new reference methods to assess relevant properties and define appropriate guidelines. It is important to perform studies of cellular uptake and cellular response to nanoparticles. From practical and ethical viewpoints relevant in vitro-based assays is preferable for initial screening purposes. Confocal Raman spectroscopy is a label-free technique which here is used to study nanoparticle-exposed lung epithelial cells (A549). The technique provides chemically selective identification of biological and inorganic compounds and intracellular distributions in living cells down to ~1 µm³ spatial resolution. Here we report on cellular response to titanium dioxide (TiO²) and goethite (a-FeO(OH)) nanoparticles in A549 cells subjected to varying times of exposures. Data is here collected in everal parts of the cells thus forming a hyperspectral image from which information is extracted using hyperspectral data analysis. The possibility to discriminate between fundamental molecular vibrations originating from DNA, proteins and membranes on control cells and particle exposed cells and quantitatively classify the spectral response by hyperspectral multivariate data analysis is discussed.