Differential pulmonary in vitro toxicity of two small-sized polyvinylpyrrolidone-coated silver nanoparticles

ABSTRACT

Silver nanoparticles (AgNP), with their important properties, are being used in a range of sectors from industry to medicine, leading to increased human exposure. Hence, their toxicity potential needs to be comprehensively evaluated. It was postulated that within small-sized (≤20 nm) polyvinylpyrrolidone-coated silver nanoparticles (PVP-AgNP), minor size differences may significantly induce different toxicity profiles and involve varying cellular pathways. Therefore, the aim of this study was to examine the influence of differing size AgNP with 10 nm (AgNP10) and 20 nm (AgNP20) (up to 100 µg/ml), as well as to ionic silver as AgNO₃ for 24 and 48 h, using the human lung cell line A549. The effects on cell viability, proliferation, apoptosis, DNA damage and cell cycle dynamics were assessed. Results for both time periods showed that for low concentrations (<5 µg/ml), AgNP20 were more cytotoxic than AgNP10, however, at higher doses, AgNP10 exhibited higher toxicity. For concentrations >50 µg/ml, AgNP10 induced severe DNA damage (comet class 3–4), cell cycle arrest at G₂ phase and late-stage apoptosis, while AgNP20 induced cell cycle arrest at S phase and an increase in the percentage sub-G_1, which did not recover after 48 h, and late-stage apoptosis/necrosis. In longer-term exposures, the greater impairment in colony formation due to AgNP exposure than to silver ion supports that nanotoxicity is not exclusively due to the released ion. Data suggest that toxicity mediated by small AgNP (≤20 nm) in lung cells is not only dependent on the level of particle internalization, but also on AgNP size and concentration, which may involve varying pathways as targets.

Acknowledgments

Thanks are due, for the financial support, to CESAM (UID/AMB/50017), to FCT/MEC through national funds and the co-funding by the FEDER, within the PT2020 Partnership Agreement and COMPETE. Funding to the project PTDC/AAC-AMB/113649 by FEDER through COMPETE and by national funds through FCT (Fundação para a Ciência e a Tecnologia). FCT-awarded grants to Fernanda Rosário (SFRH/BD/91270/2012) and Helena Oliveira (SFRH/BPD/111736/2015) are greatly acknowledged.

Additional information

Funding

This work was supported by the Fundação para a Ciência e a Tecnologia [CESAM (UID/AMB/50017),PTDC/AAC-AMB/113649,SFRH/BD/91270/2012,SFRH/BPD/111736/2015]