Quantitative elemental bioimaging: an antibody-based double-labelling method to quantify the cell-specific distribution of silver nanoparticles in lung tissue sections

Abstract

Silver nanoparticles (Ag-NP) are contained in many consumer products although their uptake especially by respiration bears potential risks for human health. Quantitative data about the systemic distribution of Ag-NP at the cellular level is strongly required to better understand the mode of action and to create meaningful in vitro models. In this paper we present a novel approach to identify cells in tissue sections by mass spectrometry imaging. Starting with a specific antibody bound to a cell marker protein we employed a double labelling strategy: a conventional secondary fluorescent antibody staining is followed by a labelling with a colloidal gold-coupled antibody directed against the same primary antibody. This allows identification of, e.g., regions of interest with conventional fluorescence microscopy and, thereafter, to detect identified cells by elemental mass spectrometry. The strategy circumvents the necessity to allocate mass-based signals to microscopic images. Unlike cost-intensive lanthanide-labelling the method is applicable to monoclonal and polyclonal primary antibodies. With this approach we confirmed the uptake of silver nanoparticles in alveolar macrophages and alveolar septal structures.