Levy Max, Courtney Colleen M, Chowdhury Partha P, Ding Yuchen, Grey Emerson L, Goodman Samuel M, Chatterjee Anushree, Nagpal Prashant
Chemical and Biological Engineering, University of Colorado Boulder, Boulder, Colorado 80303, United States.
Renewable and Sustainable Energy Institute, University of Colorado Boulder, Boulder, Colorado 80303, United States.
ACS Appl Bio Mater. 2018 Aug 20;1(2):529-537. doi: 10.1021/acsabm.8b00292. Epub 2018 Aug 9.
Reactive oxygen species (ROS) represent a broad range of chemical species including superoxide, hydroxyl, singlet oxygen, and hydrogen peroxide. Each species behaves differently in the cellular environment. Some can play specific roles as intracellular signaling molecules, while others act primarily as indiscriminate oxidants. Several recent reports have promoted the use of exogenous ROS as therapeutic agents with applications from cancer therapies to novel antimicrobials. However, therapeutics, specifically antibiotics, should either kill or inhibit the growth of harmful cells (bacteria here) without harming the host cells, and hence selectivity of action is of vital importance. Here, we show that among different ROS, only superoxide was found to be bactericidal, killing a range of multidrug-resistant (MDR) pathogens without affecting the viability or growth of mammalian cells. Superoxide has a high thermodynamic capacity to be a strong oxidant. However, its lack of reactivity with cellular components at a physiological pH, except for the inactivation of biosynthetic enzymes containing labile iron-sulfur clusters, is key to its selectivity. The role of iron in bacterial pathogenesis also makes superoxide a strong candidate for antimicrobial therapy. Additionally, using a series of selective scavengers, we show that the superoxide radical is therapeutically effective and selective compared to other ROS like hydroxyl radicals, confirming previous results that used gene knockouts to show that superoxide selectively deactivates some enzymes rather than causing indiscriminate damage of cellular components. In our in vitro studies, intracellular superoxide generation using light-activated quantum dots yielded highly selective and effective antimicrobial action. We screened 45 clinical MDR bacterial isolates and observed inhibition/therapeutic action in all strains, highlighting the applicability of such nanoparticle superoxide therapy. These results can pave the way for rational design of nanoscale therapies as precision medicine.
活性氧（ROS）代表了广泛的化学物质，包括超氧化物、羟基、单线态氧和过氧化氢。每种物质在细胞环境中的行为都有所不同。有些可以作为细胞内信号分子发挥特定作用，而其他一些主要作为无差别氧化剂起作用。最近的几份报告推动了将外源性ROS用作治疗剂，其应用范围从癌症治疗到新型抗菌剂。然而，治疗剂，特别是抗生素，应该在不损害宿主细胞的情况下杀死或抑制有害细胞（这里指细菌）的生长，因此作用的选择性至关重要。在这里，我们表明，在不同的ROS中，只有超氧化物被发现具有杀菌作用，能杀死一系列多重耐药（MDR）病原体，而不影响哺乳动物细胞的活力或生长。超氧化物具有很高的热力学能力成为强氧化剂。然而，它在生理pH值下与细胞成分缺乏反应性，除了使含有不稳定铁硫簇的生物合成酶失活外，这是其选择性的关键。铁在细菌致病过程中的作用也使超氧化物成为抗菌治疗的有力候选者。此外，使用一系列选择性清除剂，我们表明与羟基自由基等其他ROS相比，超氧化物自由基在治疗上是有效的且具有选择性，这证实了先前使用基因敲除的结果，即超氧化物选择性地使某些酶失活，而不是对细胞成分造成无差别损伤。在我们的体外研究中，使用光激活量子点产生细胞内超氧化物具有高度选择性和有效的抗菌作用。我们筛选了45株临床多重耐药细菌分离株，并在所有菌株中观察到抑制/治疗作用，突出了这种纳米颗粒超氧化物疗法的适用性。这些结果可为作为精准医学的纳米级疗法的合理设计铺平道路。
