Background: Propagation of pathogens has considered an important health care problem due to their resistance against conventional antibiotics. The recent challenge involves the design of functional alternatives such as nanomaterials, used as antibacterial agents. Early stages of antibacterial damage caused by metallic nanoparticles (NPs) were studied by Transmission Electron Microscopy (TEM) and combined Scanning Transmission Electron Microscopy with High Angle Annular Dark Field (STEM-HAADF), aiming to contribute to the elucidation of the primary antibacterial mechanism of metallic NPs.

Methods: We analyze the NPs morphology by TEM and their antibacterial activity (AA) with different amounts of Ag and Cu NPs. Cultured P. aeruginosa were interacted with both NPs and processed by TEM imaging to determine NPs adhesion into bacteria wall. Samples were analyzed by combined STEM-HAADF to determine the NPs penetration into bacterium and elemental mapping were done.

Results: Both NPs displays AA depending on NPs concentration. TEM images show NPs adhesion on bacterial cells, which produces morphological changes in the structure of the bacteria. STEMHAADF also proves the NPs adhesion and penetration by intracellular localization, detecting Ag/Cu species analyzed by elemental mapping. Moreover, the relative amount of phosphorus (P) and sulfur (S) increases slightly in P. aeruginosa with the presence of NPs. These elements are associated with damaged proteins of the outer cell membrane.

Conclusions: Combined microscopy analyses suggest that the early stages of antibacterial damage caused by alteration of bacterial cell wall, and can be considered a powerful tool aiming to understand the primary antibacterial mechanism of NPs.

背景：由于病原体对常规抗生素的耐药性，病原体的繁殖被认为是一个重要的医疗保健问题。最近的挑战涉及功能性替代品的设计，例如用作抗菌剂的纳米材料。通过透射电子显微镜 (TEM) 和扫描透射电子显微镜与高角度环形暗场 (STEM-HAADF) 组合研究金属纳米粒子 (NPs) 引起的抗菌损伤的早期阶段，旨在有助于阐明主要的抗菌机制金属NPs。

方法：我们通过 TEM 分析 NPs 的形态及其在不同量的 Ag 和 Cu NPs 下的抗菌活性 (AA)。培养的铜绿假单胞菌与两种 NPs 相互作用并通过 TEM 成像处理以确定 NPs 粘附到细菌壁中。通过组合的 STEM-HAADF 分析样品以确定 NPs 渗透到细菌中并进行元素映射。

结果：两个 NP 都显示 AA，具体取决于 NP 浓度。TEM图像显示NPs粘附在细菌细胞上，从而产生细菌结构的形态变化。STEMHAADF 还通过细胞内定位证明了 NPs 的粘附和渗透，检测通过元素映射分析的 Ag/Cu 物种。此外，随着 NPs 的存在，铜绿假单胞菌中磷 (P) 和硫 (S) 的相对量略有增加。这些元素与外细胞膜的受损蛋白质有关。

结论：联合显微镜分析表明，细菌细胞壁改变引起的抗菌损伤的早期阶段，可被视为旨在了解 NPs 主要抗菌机制的有力工具。