Metabolic response of human keratinocytes to silver nanoparticles: A metabolomics study

Abstract

Silver nanoparticles (Ag-NPs) have been increasingly incorporated into biomedical and household products mainly due to their remarkable antimicrobial properties. However, there is a narrow window between the bactericidal activity of Ag-NPs and their toxicity to human cells, thus calling for an improved understanding of Ag-NPs toxicological and biological effects. By offering a detailed, non-selective screening of intra- and/or extracellular metabolites, the metabolomics approach is exquisitely valuable for unveiling unsuspected metabolic effects of nanoparticles and for obtaining new insights into their toxicity mechanisms. In this work, human epidermis keratinocytes (HaCaT cell line) grown in DMEM medium, have been exposed for 24 and 48 h to well-characterised Ag-NPs of different average diameters (10, 30 and 60 nm) at (sub)toxic doses, and their endo- and exo-metabolomes characterised by 1H Nuclear Magnetic Resonance (NMR) spectroscopy, in tandem with multivariate analysis. Cell proliferation and cytotoxicity evaluations were conducted by microscopic evaluation and MTT cell viability assay. A number of metabolites involved in different biochemical processes (e.g. antioxidative response, aminoacid and lipid metabolisms) were found to be altered upon Ag-NPs exposure, in a dose- and time-dependent manner. Ag-NPs size and aggregation pattern were also seen to influence the metabolic responses. The results show the potential of NMR metabolic profiling for highlighting new endpoint markers of Ag-NPs effects, thus demonstrating the value of metabolomics as a novel tool in the area of in vitro nanotoxicology.