Browsing by Author "Puppala, Hema L."

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    Size-dependent impacts of silver nanoparticles on the lifespan, fertility, growth, and locomotion of Caenorhabditis elegans
    (Wiley, 2014) Contreras, Elizabeth Q.; Puppala, Hema L.; Escalera, Gabriela; Zhong, Weiwei; Colvin, Vicki L.
    The increased bioavailability of nanoparticles engineered for good dispersion in water may have biological and environmental impacts. To examine this issue, the authors assessed the biological effects in nematodes as they relate to exposure to silver nanoparticles (AgNPs) of different sizes at low (1 mg/L Ag), medium (10 mg/L Ag), and high concentrations (100 mg/L Ag). Over multiple generations, the authors found that the smallest particle, at 2 nm, had a notable impact on nematode fertility. In contrast, the largest particle, at 10 nm, significantly reduced the lifespan of parent nematodes (P0) by 28.8% and over the span of 3 generations (F1–F3). In addition, a computer vision system automatically measured the adverse effects in body length and motility, which were not size-dependent.
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    Toxicity of Quantum Dots and Cadmium Salt to Caenorhabditis elegans after Multigenerational Exposure
    (American Chemical Society, 2013) Contreras, Elizabeth Q.; Cho, Minjung; Zhu, Huiguang; Puppala, Hema L.; Escalera, Gabriela; Zhong, Weiwei; Colvin, Vicki L.
    To fully understand the biological and environmental impacts of nanomaterials requires studies that address both sublethal end points and multigenerational effects. Here, we use a nematode to examine these issues as they relate to exposure to two different types of quantum dots, core (CdSe) and coreﾖshell (CdSe/ZnS), and to compare the effect to those observed after cadmium salt exposures. The strong fluorescence of the coreﾖshell QDs allowed for the direct visualization of the materials in the digestive track within a few hours of exposure. Multiple end points, including both developmental and locomotive, were examined at QD exposures of low (10 mg/L Cd), medium (50 mg/L Cd), and high concentrations (100 mg/L Cd). While the coreﾖshell QDs showed no effect on fitness (lifespan, fertility, growth, and three parameters of motility behavior), the core QDs caused acute effects similar to those found for cadmium salts, suggesting that biological effects may be attributed to cadmium leaching from the more soluble QDs. Over multiple generations, we commonly found that for lower life-cycle exposures to core QDs the parents response was generally a poor predictor of the effects on progeny. At the highest concentrations, however, biological effects found for the first generation were commonly similar in magnitude to those found in future generations.
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    When function is biological: Discerning how silver nanoparticle structure dictates antimicrobial activity
    (Cell Press, 2022) Zhang, Qingbo; Hu, Yue; Masterson, Caitlin M.; Jang, Wonhee; Xiao, Zhen; Bohloul, Arash; Garcia-Rojas, Daniel; Puppala, Hema L.; Bennett, George; Colvin, Vicki L.
    Silver nanomaterials have potent antibacterial properties that are the foundation for their wide commercial use as well as for concerns about their unintended environmental impact. The nanoparticles themselves are relatively biologically inert but they can undergo oxidative dissolution yielding toxic silver ions. A quantitative relationship between silver material structure and dissolution, and thus antimicrobial activity, has yet to be established. Here, this dissolution process and associated biological activity is characterized using uniform nanoparticles with variable dimension, shape, and surface chemistry. From this, a phenomenological model emerges that quantitatively relates material structure to both silver dissolution and microbial toxicity. Shape has the most profound influence on antibacterial activity, and surprisingly, surface coatings the least. These results illustrate how material structure may be optimized for antimicrobial properties and suggest strategies for minimizing silver nanoparticle effects on microbes.