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Oxidized Activated Charcoal Nanoparticles as Catalytic Superoxide Dismutase Mimetics: Evidence for Direct Participation of an Intrinsic Radical
ACS Applied Nano Materials ( IF 5.3 ) Pub Date : 2020-06-29 , DOI: 10.1021/acsanm.0c01285 Gang Wu 1 , Emily A. McHugh , Vladimir Berka 1 , Weiyin Chen , Zhe Wang , Jacob L. Beckham , Paul J. Derry 2, 3 , Trenton Roy , Thomas A. Kent 3, 4 , James M. Tour , Ah-Lim Tsai 1
ACS Applied Nano Materials ( IF 5.3 ) Pub Date : 2020-06-29 , DOI: 10.1021/acsanm.0c01285 Gang Wu 1 , Emily A. McHugh , Vladimir Berka 1 , Weiyin Chen , Zhe Wang , Jacob L. Beckham , Paul J. Derry 2, 3 , Trenton Roy , Thomas A. Kent 3, 4 , James M. Tour , Ah-Lim Tsai 1
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The mechanism for carbon-based superoxide dismutase (SOD) nanomimetics is not known, hindering the optimization of this potentially clinically useful feature. Here we studied oxidized activated charcoal (OAC) prepared by fuming nitric acid oxidation of activated charcoal and characterized its properties. The OAC nanoparticles have sizes 5–30 nm and are highly water-soluble. The OACs are strong SOD mimetics with a kcat = 2.1 × 105 s–1 at pH 12.7 and ∼108 M–1 s–1 rate constants at pH 8.5, having great potential in therapeutic application for disorders with pathological superoxide levels. Electron paramagnetic resonance (EPR) indicates that resting OACs are fully oxidized, exhibiting a stoichiometric level of an intrinsic radical. The OACs can be reduced with superoxide, leading to a decreased level of the intrinsic radical; however, the reduction is incomplete even at high superoxide levels. This outcome was predicted by a simple two-step SOD reaction mechanism using the species containing the intrinsic radical as the fully oxidized state. Pretreatment of the OACs with superoxide causes little change to its SOD activity, indicating that a stoichiometric amount of the intrinsic radical is not mandatory for full activity. This study indicates the direct participation of the intrinsic radical in the catalytic turnover of a highly active SOD-like nanozyme.
中文翻译：
氧化的活性炭纳米粒子作为催化的超氧化物歧化酶模拟物：直接参与本征自由基的证据。
碳基超氧化物歧化酶（SOD）纳米模拟物的机制尚不清楚，这阻碍了此潜在临床有用功能的优化。在这里，我们研究了通过将活性炭发烟硝酸氧化而制备的氧化活性炭（OAC），并对其特性进行了表征。OAC纳米粒子的尺寸为5–30 nm，并且高度水溶性。的OACS是强SOD模拟物与ķ猫= 2.1×10 5小号-1在pH 12.7和〜10 8中号-1小号-1pH值恒定在8.5，在具有病理性超氧化物水平疾病的治疗应用中具有巨大潜力。电子顺磁共振（EPR）表明静止的OAC被完全氧化，表现出化学计量水平的固有自由基。OAC可以用超氧化物还原，导致固有自由基的含量降低；但是，即使在高超氧化物水平下，还原也不完全。通过使用包含固有自由基作为完全氧化态的物质的简单两步SOD反应机理可以预测此结果。用超氧化物预处理OAC几乎不会改变其SOD活性，这表明化学计量的内在自由基对于全部活性而言不是强制性的。
更新日期：2020-07-24
中文翻译：
氧化的活性炭纳米粒子作为催化的超氧化物歧化酶模拟物：直接参与本征自由基的证据。
碳基超氧化物歧化酶（SOD）纳米模拟物的机制尚不清楚，这阻碍了此潜在临床有用功能的优化。在这里，我们研究了通过将活性炭发烟硝酸氧化而制备的氧化活性炭（OAC），并对其特性进行了表征。OAC纳米粒子的尺寸为5–30 nm，并且高度水溶性。的OACS是强SOD模拟物与ķ猫= 2.1×10 5小号-1在pH 12.7和〜10 8中号-1小号-1pH值恒定在8.5，在具有病理性超氧化物水平疾病的治疗应用中具有巨大潜力。电子顺磁共振（EPR）表明静止的OAC被完全氧化，表现出化学计量水平的固有自由基。OAC可以用超氧化物还原，导致固有自由基的含量降低；但是，即使在高超氧化物水平下，还原也不完全。通过使用包含固有自由基作为完全氧化态的物质的简单两步SOD反应机理可以预测此结果。用超氧化物预处理OAC几乎不会改变其SOD活性，这表明化学计量的内在自由基对于全部活性而言不是强制性的。
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