Bren School of Environmental Science & Management, University of California, Santa Barbara, CA 93106, USA.
Analyst. 2014 Mar 7;139(5):954-63. doi: 10.1039/c3an01648j. Epub 2013 Dec 17.
Because of microbial resistance to conventional antibiotics, there is increasing interest in silver, including silver nanoparticles (nano-Ag), in antimicrobial applications. However, questions remain regarding the relative roles of nano-Ag particles, versus Ag(+) ions released from nano-Ag dissolution, in imparting bacterial toxicity. Here, we developed a novel nano-Ag that, based on its cysteine cap, was expected to dissolve slowly and thus potentially allow for differentiating nanoparticle, versus ionic, effects of Ag. The nano-Ag was systematically tested for its differential toxicity to Escherichia coli and Pseudomonas aeruginosa. Bacterial growth, reactive oxygen species (ROS) generation, particle dissolution, cellular electron transfer activity, and cell membrane damage and potential were evaluated. In minimal growth medium, E. coli and P. aeruginosa growth were slowed at 100 mg L(-1) (0.93 mM) and 5 mg L(-1) (0.046 mM), respectively; P. aeruginosa was completely inhibited at and above 10 mg L(-1) (0.093 mM). For both strains, toxicity was associated with ROS and cell membrane damage. Based on comparisons to AgNO3 exposures, toxicity from nano-Ag was due to Ag(+) ions and not intact nano-Ag, even though nanoparticle dissolution was less than 2% in minimal growth medium. Because of their stability and slow Ag(+) ion release, the cysteine-capped nano-Ag particles here are useful to antimicrobial applications. Additionally, our systematic approach to evaluating toxicity, membrane damage, and ROS generation can be applied with other nanomaterials and bacteria.
由于传统抗生素的微生物耐药性，人们对银越来越感兴趣，包括银纳米粒子（nano-Ag），用于抗菌应用。然而，关于纳米银颗粒与纳米银溶解释放的银（+）离子在赋予细菌毒性方面的相对作用，仍存在一些问题。在这里，我们开发了一种新型的纳米银，基于其半胱氨酸帽，预计其溶解速度会很慢，因此有可能区分纳米粒子与银的离子效应。我们系统地测试了纳米银对大肠杆菌和铜绿假单胞菌的毒性差异。评估了细菌生长、活性氧（ROS）生成、颗粒溶解、细胞电子转移活性以及细胞膜损伤和通透性。在最低生长培养基中，大肠杆菌和铜绿假单胞菌的生长分别在 100 mg/L（0.93 mM）和 5 mg/L（0.046 mM）时减缓；铜绿假单胞菌在 10 mg/L（0.093 mM）及以上时完全被抑制。对于这两种菌株，毒性与 ROS 和细胞膜损伤有关。与 AgNO3 暴露的比较表明，纳米银的毒性来自于银（+）离子，而不是完整的纳米银，即使在最低生长培养基中，纳米银的溶解不到 2%。由于其稳定性和缓慢的银（+）离子释放，这里的半胱氨酸封端的纳米银颗粒可用于抗菌应用。此外，我们系统地评估毒性、膜损伤和 ROS 生成的方法可应用于其他纳米材料和细菌。
