Nanoparticle size and combined toxicity of TiO₂ and DSLS (surfactant) contribute to lysosomal responses in digestive cells of mussels exposed to TiO₂ nanoparticles

Abstract

The aim of this investigation was to understand the bioaccumulation, cell and tissue distribution and biological effects of disodium laureth sulfosuccinate (DSLS)-stabilised TiO₂ nanoparticles (NPs) in marine mussels, Mytilus galloprovincialis. Mussels were exposed in vivo to 0.1, 1 and 10 mg Ti/L either as TiO₂ NPs (60 and 180 nm) or bulk TiO₂, as well as to DSLS alone. A significant Ti accumulation was observed in mussels exposed to TiO₂ NPs, which were localised in endosomes, lysosomes and residual bodies of digestive cells, and in the lumen of digestive tubules, as demonstrated by ultrastructural observations and electron probe X-ray microanalysis. TiO₂ NPs of 60 nm were internalised within digestive cell lysosomes to a higher extent than TiO₂ NPs of 180 nm, as confirmed by the quantification of black silver deposits after autometallography. The latter were localised mainly forming large aggregates in the lumen of the gut. Consequently, lysosomal membrane stability (LMS) was significantly reduced upon exposure to both TiO₂ NPs although more markedly after exposure to TiO₂-60 NPs. Exposure to bulk TiO₂ and to DSLS also affected the stability of the lysosomal membrane. Thus, effects on the lysosomal membrane depended on the nanoparticle size and on the combined biological effects of TiO₂ and DSLS.

• Bioaccumulation
• cell and tissue distribution
• lysosomal membrane destabilisation

Acknowledgements

TEM and X-ray microanalysis were carried out at the Centre for Ultrastructural Imaging, King's College London. SGIker technical and human support (UPV/EHU, MICINN, GV/EJ, ESF) is gratefully acknowledged.

Disclosure statement

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

This work was funded by EU 7th FP (NanoReTox project, CP-FP 214478-2), Spanish Ministry (NanoCancer project CTM2009-13477), Basque Government (consolidated research group IT810-13) and University of the Basque Country (UFI 11/37 and PhD fellowship to A. JR).