Detonation nanodiamond toxicity in human airway epithelial cells is modulated by air oxidation

• Bioactive detonation nanodiamonds (DNDs) were heated at 425 °C in air or in N2.
• Air oxidation increased DND oxygen and carboxyl content and lowered its zeta potential.
• These changes were accompanied by decreased DND activity towards human airway cells.
• The findings point to chemical determinants of toxicity of carbonaceous nanomaterials.

Detonation nanodiamonds (DNDs), a nanomaterial with an increasing range of industrial and biomedical applications, have previously been shown to induce a pro-inflammatory response in cultured human airway epithelial cells (HAECs). We now show that surface modifications induced by air oxidation of DND (AO-DND), including an increase in oxygen content, formation of carboxylic groups associated with the appearance of high negative zeta potential and a decrease in unpaired electron content, are accompanied by a significant loss of bioactivity, as measured by levels of interleukin-8 mRNA in HAEC. These findings are relevant to the identification of chemical determinants and molecular mechanisms of the inhalational toxicity of carbonaceous nanomaterials.