Inorganic nanoparticles that mimic the activity of enzymes are promising systems for biomedical applications. However, they cannot distinguish between healthy and damaged tissues, which could cause undesired effects. Natural enzymes avoid this drawback via activation triggered by specific biochemical events in the body. Inspired by this strategy, we proposed an artificial cerium-based proenzyme system that could be activated to a superoxide dismutase-like form using H₂O₂ as the trigger. To achieve this goal, an innovative and easy strategy to synthesize Ce(OH)₃ nanoparticles as artificial proenzymes was developed using a lyotropic liquid crystal composed of phytantriol, which was essential to maintain their stability at physiological pH. The transmission electron microscopy measurements showed that the Ce(OH)₃ nanoparticles were as small as 2 nm. The nanoparticles were fitted into the tiny aqueous channels of the liquid crystal matrix, which presented a Pn3m space group. X-ray absorption near edge structure measurements were used to determine the Ce(III) fraction of the proenzyme-like nanoparticles, which was around 85%. The Ce(III) fraction dramatically dropped to around 5% after contact with H₂O₂ because of the conversion of Ce(OH)₃ to CeO_(2−x) nanoparticles. The CeO_(2−x) nanoparticles showed superoxide dismutase-like activity in contrast to the inactive Ce(OH)₃ form. The proof of concept presented in this work opens up new possibilities for using nanoparticles as artificial proenzymes that are activated by a biochemical trigger in vivo.

中文翻译：

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限制在溶致液晶中的基于铈的人工酶：合成策略和按需激活†

模仿酶活性的无机纳米颗粒是有前途的生物医学应用系统。但是，它们无法区分健康组织和受损组织，这可能会导致不良后果。天然酶通过体内特定生化事件触发的活化作用避免了这种缺陷。受此策略的启发，我们提出了一种基于铈的人工酶系统，该系统可以使用H ₂ O ₂作为触发因子激活为超氧化物歧化酶样形式。为了实现这一目标，需要一种创新且简便的策略来合成Ce（OH）₃使用由植物三醇组成的溶致液晶，开发了纳米颗粒作为人工酶，这对于在生理pH值下保持其稳定性至关重要。透射电子显微镜测量结果显示Ce（OH）₃纳米颗粒小至2 nm。将纳米颗粒装入液晶基体的微小水通道中，该通道呈现Pn 3 m空间群。X射线吸收在边缘结构附近的测量被用来确定类似酶原的纳米颗粒的Ce（III）比例，约为85％。与H ₂ O ₂接触后，Ce（III）的比例急剧下降至5％左右因为Ce（OH）₃转化为CeO _{（2- x）}纳米颗粒。与无活性的Ce（OH）₃形式相比，CeO _{（2- x）}纳米粒子显示出超氧化物歧化酶样活性。这项工作中提出的概念证明为利用纳米粒子作为人工酶提供了新的可能性，纳米粒子被体内生化触发器激活。