Co-exposure with fullerene may strengthen health effects of organic industrial chemicals.

Maili Lehto,Janne Jänis,Tomasz Róg,Jarkko Tornaeus,Harri Alenius,Esa Vanhala,Topi Karilainen,Olli Laine,Ilpo Vattulainen,Oana Cramariuc,Helena Taberman,Danilo Roccatano

doi:10.1371/journal.pone.0114490

Abstract

In vitro toxicological studies together with atomistic molecular dynamics simulations show that occupational co-exposure with C60 fullerene may strengthen the health effects of organic industrial chemicals. The chemicals studied are acetophenone, benzaldehyde, benzyl alcohol, m-cresol, and toluene which can be used with fullerene as reagents or solvents in industrial processes. Potential co-exposure scenarios include a fullerene dust and organic chemical vapor, or a fullerene solution aerosolized in workplace air. Unfiltered and filtered mixtures of C60 and organic chemicals represent different co-exposure scenarios in in vitro studies where acute cytotoxicity and immunotoxicity of C60 and organic chemicals are tested together and alone by using human THP-1-derived macrophages. Statistically significant co-effects are observed for an unfiltered mixture of benzaldehyde and C60 that is more cytotoxic than benzaldehyde alone, and for a filtered mixture of m-cresol and C60 that is slightly less cytotoxic than m-cresol. Hydrophobicity of chemicals correlates with co-effects when secretion of pro-inflammatory cytokines IL-1β and TNF-α is considered. Complementary atomistic molecular dynamics simulations reveal that C60 co-aggregates with all chemicals in aqueous environment. Stable aggregates have a fullerene-rich core and a chemical-rich surface layer, and while essentially all C60 molecules aggregate together, a portion of organic molecules remains in water.

Highlights

Fullerenes belong to carbon nanomaterials which are carbon allotropes first discovered in 1985 [1]
Average diameters of aggregates measured by dynamic light scattering (DLS) did not differ significantly between the suspension of pure fullerene and those of fullerene with organic chemicals
Results from our atomistic molecular dynamics (MD) simulations agree with previous results from theoretical and experimental studies where highly hydrophobic C60 and C70 readily aggregate in water and co-aggregate with organic molecules [12, 45,46,47,48]

Summary

Introduction

Fullerenes belong to carbon nanomaterials which are carbon allotropes first discovered in 1985 [1]. They have been under extensive research ever since and fullerene-based materials have already been used in numerous commercial applications [2]. In previous in vivo and in vitro studies [6,7,8], pure unmodified fullerenes have not shown any severe toxicological effects. The most severe findings have been explained by traces of tetrahydrofuran (THF) which is often used as solvent in preparation of stable fullerene suspensions for toxicological studies [9,10,11]

Methods

Results

Discussion

Conclusion