Ligands that accelerate nanoceria dissolution may greatly affect its fate and effects. This project assessed the carboxylic acid contribution to nanoceria dissolution in aqueous, acidic environments. Nanoceria has commercial and potential therapeutic and energy storage applications. It biotransforms in vivo. Citric acid stabilizes nanoceria during synthesis and in aqueous dispersions. In this study, citrate-stabilized nanoceria dispersions (∼4 nm average primary particle size) were loaded into dialysis cassettes whose membranes passed cerium salts but not nanoceria particles. The cassettes were immersed in iso-osmotic baths containing carboxylic acids at pH 4.5 and 37 °C, or other select agents. Cerium atom material balances were conducted for the cassette and bath by sampling of each chamber and cerium quantitation by ICP-MS. Samples were collected from the cassette for high-resolution transmission electron microscopy observation of nanoceria size. In carboxylic acid solutions, nanoceria dissolution increased bath cerium concentration to >96% of the cerium introduced as nanoceria into the cassette and decreased nanoceria primary particle size in the cassette. In solutions of citric, malic, and lactic acids and the ammonium ion ∼15 nm, ceria agglomerates persisted. In solutions of other carboxylic acids, some select nanoceria agglomerates grew to ∼1 micron. In carboxylic acid solutions, dissolution half-lives were 800-4000 h; in water and horseradish peroxidase they were ≥55,000 h. Extending these findings to in vivo and environmental systems, one expects acidic environments containing carboxylic acids to degrade nanoceria by dissolution; two examples would be phagolysosomes and in the plant rhizosphere.

中文翻译：

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羧酸加速酸性环境介导的纳米氧化铈的溶解。

加速纳米二氧化铈溶解的配体可能会极大地影响其命运和影响。该项目评估了羧酸在水性酸性环境中对纳米氧化铈溶解的贡献。纳米氧化铈具有商业和潜在的治疗和能量存储应用。它在体内生物转化。柠檬酸可在合成过程中和在水分散液中稳定纳米氧化铈。在这项研究中，将柠檬酸盐稳定的纳米氧化铈分散液（平均初级粒径约为4 nm）装入透析盒中，该透析盒的膜可通过铈盐而不通过纳米氧化铈颗粒。将盒浸入含有pH 4.5和37°C的羧酸或其他选择剂的等渗浴中。通过对每个腔室进行采样并通过ICP-MS对铈进行定量，从而对样品盒和镀液进行了铈原子物质平衡。从盒中收集样品，用于纳米二氧化铈尺寸的高分辨率透射电子显微镜观察。在羧酸溶液中，纳米二氧化铈溶解使浴中的铈浓度增加到>作为纳米二氧化铈引入盒中的铈的> 96％，并降低了纳米二氧化铈在盒中的一次粒径。在柠檬酸，苹果酸和乳酸以及约15 nm的铵离子溶液中，二氧化铈附聚物持续存在。在其他羧酸的溶液中，某些精选的纳米氧化铈附聚物长到了约1微米。在羧酸溶液中，溶解半衰期为800-4000小时；在水中和辣根过氧化物酶中，它们≥55,000 h。将这些发现扩展到体内和环境系统后，人们期望包含羧酸的酸性环境通过溶解而降解纳米氧化铈。