Surface modification by different
quaternary ammonium compounds (QAC) makes nanoclays more compatible with various polymeric matrices, thereby expanding their potential applications. The growing industrial use of nanoclays could potentially pose a health risk for workers. Here, we assessed how surface modification of nanoclays modulates their pulmonary toxicity. An in vitro screening of the unmodified nanoclay
Bentonite (
montmorillonite) and four organomodified nanoclays (ONC); coated with various QAC, including
benzalkonium chloride (BAC), guided the selection of the materials for the in vivo study. Mice were exposed via a single intratracheal instillation to 18, 54, and 162 µg of unmodified
Bentonite or dialkyldimethyl-
ammonium-coated ONC (NanofilSE3000), or to 6, 18, and 54 µg of a BAC-coated ONC (Nanofil9), and followed for one, 3, or 28 days. All materials induced dose- and time-dependent responses in the exposed mice. However, all doses of
Bentonite induced larger, but reversible,
inflammation (BAL neutrophils) and
acute phase response (Saa3 gene expression in lung) than the two ONC. Similarly, highest levels of
DNA strand breaks were found in BAL cells of mice exposed to
Bentonite 1 day post-exposure. A significant increase of
DNA strand breaks was detected also for NanofilSE3000, 3 days post-exposure. Only mice exposed to
Bentonite showed increased Tgf-β gene expression in lung,
biomarker of pro-fibrotic processes and hepatic extravasation, 3 days post-exposure. This study indicates that
Bentonite treatment with some QAC changes main physical-chemical properties, including shape and surface area, and may decrease their pulmonary toxicity in exposed mice.