Toxicity evaluation of nanocrystalline silver-impregnated coated dressing on the life cycle of worm Caenorhabditis elegans

There has been a growing demand for nanomaterials in recent years due to the production of cosmetics and pharmaceuticals, among other products. Even with this high demand and use, information on the toxicity of nanomaterials is still limited. Silver nanoparticles are used as a bactericide and are present in drugs, surgical materials, coated dressings, tissues and other products. Improper disposal of these items after use may cause toxicological effects on organisms in the environment. To evaluate the potential environmental hazard of nanosilver-coated dressings, the nematode <i>Caenorhabditis elegans</i> was chosen as a test organism. The assays were conducted in 24-well plates that contain four different sizes of coated dressing to obtain different concentrations. L1 and L4 <i>C. elegans</i> larval stages were exposed to these nanosilver concentrations. Dressing cutouts were arranged between two layers of agar for 3 days and <i>Escherichia coli</i> (OP 50 strain) was added as food source for the worms. After the exposure period, growth, reproduction, fertility, silver concentration in the medium and the concentration of reactive oxygen species (ROS) in the worms were evaluated. Scanning and transmission electron microscopy analyses were performed on the coated dressings, as well as analyses of zeta potential, ionic release and antibacterial power in two bacterial strains (<i>Pseudomonas aeruginosa</i> and <i>Staphylococcus aureus</i>)<i>.</i> It was verified the antibacterial power of the coated dressing, in both bacteria strains tested. Characterization of the coated dressing indicated heterogeneous nanoparticles, as well as distinct zeta potentials for the medium in water and saline medium (0.9 % NaCl). L1 larval worms exposed to nanosilver-coated dressing showed a high ROS concentration and reductions in growth, fertility and reproduction. Worms exposed to the coated dressing during the L4 stage showed almost no response. Overall, the obtained results indicate the potential environmental hazard of nanosilver-coated dressings.

近年来，随着化妆品、药品及其他各类产品的生产制造，纳米材料的市场需求持续攀升。尽管纳米材料的应用与需求量均处于高位，但有关其毒性的公开信息仍较为匮乏。银纳米粒子（silver nanoparticles）常被用作杀菌剂，广泛应用于药品、手术耗材、涂层敷料、生物组织制品等诸多领域与产品中。若该类产品使用后处置不当，可能会对环境中的生物体产生毒理学危害。为评估纳米银涂层敷料的潜在环境危害，本研究选取秀丽隐杆线虫（Caenorhabditis elegans）作为受试生物。实验采用24孔板开展，设置四种不同规格的涂层敷料以制备梯度浓度的受试体系。将L1期与L4期的秀丽隐杆线虫暴露于不同浓度的纳米银环境中。将敷料切块置于两层琼脂培养基之间培养3天，并添加大肠杆菌（Escherichia coli，OP50菌株）作为线虫的食物来源。暴露培养结束后，本研究对受试线虫的生长状态、繁殖能力、生育水平、培养基中银离子浓度以及线虫体内活性氧（reactive oxygen species, ROS）水平进行了系统性评估。此外，研究团队还针对涂层敷料开展了扫描电镜与透射电镜表征分析，并检测了其Zeta电位（zeta potential）、离子释放量，以及对两种受试菌株——铜绿假单胞菌（Pseudomonas aeruginosa）与金黄色葡萄球菌（Staphylococcus aureus）的抗菌性能。实验结果证实，该纳米银涂层敷料对两种受试菌株均具备显著的抗菌活性。涂层敷料的表征结果显示其纳米粒子分布不均，且在水介质与0.9%生理盐水介质中的Zeta电位存在显著差异。暴露于纳米银涂层敷料的L1期线虫体内活性氧水平显著升高，同时出现生长受抑、生育能力与繁殖能力下降的现象；而L4期暴露于该涂层敷料的线虫则几乎未出现明显生理响应。综合上述实验结果，本研究证实纳米银涂层敷料具备潜在的环境危害风险。