Exposure to light is a key parameter that influences the chemical interactions and microbial stress of engineered nanomaterials (ENMs). Yet, the photochemistry and phototoxic stress responses of many ENMs and ENM mixtures have not been adequately detailed. We exposed E. coli bacteria to binary combinations of n-TiO₂ (a stable metal oxide) with different plasmonic metal ENMs (n-Ag, n-Au, or n-Pt) in a natural aqueous medium under light and dark conditions. Using ATP level and cell membrane integrity probes, we measure the toxic stress due to these ENM mixtures. We previously found that under dark conditions, n-TiO₂ attenuates the toxic stress due to low concentrations of n-Ag (<20 μg L⁻¹) via adsorption of Ag⁺. However, mixtures containing n-Au or n-Pt produce no difference in toxic stress responses with and without n-TiO₂ in the dark. In contrast, under simulated solar irradiation, we observed that n-Ag, n-Au, and n-Pt each with n-TiO₂ cause synergistic toxic stress. The n-Ag/n-TiO₂ combination causes the greatest phototoxicity, followed by n-Au/n-TiO₂ and then n-Pt/n-TiO₂. Measurements of photocatalytic production of reactive oxygen species reveal that irradiation of n-Ag or n-Au with n-TiO₂ yields synergistic production of superoxide anion and hydrogen peroxide. The photochemical interactions of these ENMs, governed by metal ENM solubility and localized surface plasmon resonance, provide mechanistic insight into the amplified photoactivity of mixtures.

中文翻译：

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由于工程纳米材料的混合物，光在减轻微生物压力中的关键作用†

曝光是影响工程纳米材料（ENM）的化学相互作用和微生物应力的关键参数。然而，许多ENM和ENM混合物的光化学和光毒性胁迫反应还没有足够详细。我们在自然水介质中，在明暗条件下，将大肠杆菌暴露于n-TiO ₂（一种稳定的金属氧化物）与不同等离激元金属ENM（n-Ag，n-Au或n-Pt）的二元组合。使用ATP水平和细胞膜完整性探针，我们可以测量由于这些ENM混合物引起的毒性应激。我们先前发现在黑暗条件下，n-TiO ₂通过吸附Ag降低了低浓度的n-Ag（<20μgL ^-1）引起的毒性应力。⁺。然而，在黑暗中有或没有n-TiO _2的情况下，含有n-Au或n-Pt的混合物在毒性应力响应方面均没有差异。相反，在模拟的太阳辐射下，我们观察到n-Ag，n-Au和n-Pt分别与n-TiO ₂引起协同毒性应力。n-Ag / n-TiO ₂组合引起最大的光毒性，其次是n-Au / n-TiO ₂，然后是n-Pt / n-TiO ₂。测量活性氧的光催化产生量表明，用n-TiO ₂辐照n-Ag或n-Au产生超氧阴离子和过氧化氢的协同生产。这些ENM的光化学相互作用受金属ENM溶解度和局部表面等离振子共振的支配，为深入研究混合物的光活性提供了机械原理。