The influence of organic modification on the cytotoxicity of clay particles to keratinocytes, hepatocytes and macrophages; an investigation towards the safe use of polymer-clay nanocomposite packaging

Organically modified clays can be used as nanofillers in polymer-clay nanocomposites to create bio-based packaging with improved strength and barrier properties. The impact of organic modification on the physico-chemical properties and toxicity of clays has yet to be fully investigated but is essential to ensure their safe use. Two organoclays, named N116_HDTA and N116_TMSA, were prepared using a commercially available sodium bentonite clay and the organic modifiers hexadecyl trimethyl ammonium bromide (HDTA) and octadecyl trimethyl ammonium chloride (TMSA). An in vitro hazard assessment was performed using HaCaT skin cells, C3A liver cells, and J774.1 macrophage-like cells. Organic modification with HDTA and TMSA increased the hazard potential of the organoclays in all cell models, as evidenced by the higher levels of cytotoxicity measured. N116_TMSA caused the greatest loss in viability with IC50 values of 3.2, 3.6 and 6.1 μg/cm2 calculated using J774.1, HaCaT and C3A cell lines, respectively. Cytotoxic effects were dictated by the amount of free or displaced organic modifier present in the exposure suspensions. The parent bentonite clay also caused distinct cytotoxic effects in J774.1 macrophage-like cells with associated TNF-α release. Such information on the hazard profile of organoclays, can feed into risk assessments for these materials.