An official website of the United States government
Use of complex metal oxide nanoparticles has drastically risen in recent years, especially due to their utility in electric vehicle batteries. However, use of these materials has outpaced our understanding of how they might affect environmental organisms, which they could encounter through release during manufacture, use, and disposal. In particular, little is known about the effects of chronic exposure to complex metal oxide nanoparticles. Here, we have focused on an environmentally-relevant bacterial species, Shewanella oneidensis, which is ubiquitous in nature and responsible for bioremediation of heavy metals, and assessed the toxic effects of nanoscale lithiated nickel manganese cobalt oxide (NMC), which is an emerging battery cathode material for electronic devices. We previously reported that chronic exposure of S. oneidensis to NMC results in the emergence of an adaptive phenotype where the bacteria are able to tolerate otherwise lethal concentrations of NMC. In the present study, we aim to investigate the role of reactive oxygen species (ROS) and changes in phenotype of the NMC-adapted bacterial population. We found that NMC-exposed bacteria possess ROS-containing membrane vesicles, as well as an increased propensity to generate random DNA mutations and harbor other DNA damage. Thus, our data indicate substantial genetic-level variation in bacteria that results from chronic exposure to toxic complex metal oxide nanomaterials.
more »
« less
Colloidal stabilization of hydrophobic InSe 2D nanosheets in a model environmental aqueous solution and their impact on Shewanella oneidensis MR-1
Semiconductor InSe 2D nanomaterials have emerged as potential photoresponsive materials for broadly distributed photodetectors and wearable electronics technologies due to their high photoresponsivity and thermal stability. This paper addresses an environmental concern about the fate of InSe 2D nanosheets when disposed and released into the environment after use. Semiconducting materials are potentially reactive and often form environmentally damaging species, for example reactive oxygen and nitrogen species, when degraded. InSe nanosheets are prepared using a semi bottom-up approach which involves a reaction between indium and selenium precursors at elevated temperature in an oxygen-free environment to prevent oxidation. InSe nanosheets are formed as a stable intermediate with micrometer-sized lateral dimensions and a few monolayer thickness. The InSe 2D nanosheets are obtained when the reaction is stopped after 30 minutes by cooling. Keeping the reaction at elevated temperature for a longer period, for example 60 minutes leads to the formation of InSe 3D nanoparticles of about 5 nm in diameter, a thermodynamically more stable form of InSe. The paper focuses on the colloidal stabilization of InSe nanosheets in an aqueous solution that contains epigallocatechin gallate (EGCG), a natural organic matter (NOM) simulant. We show that EGCG coats the surface of the hydrophobic, water-insoluble InSe nanosheets via physisorption. The formed EGCG-coated InSe nanosheets are colloidally stable in aqueous solution. While unmodified semiconducting InSe nanosheets could produce reactive oxygen species (ROS) when illuminated, our study shows low levels of ROS generation by EGCG-coated InSe nanosheets under ambient light, which might be attributed to ROS quenching by EGCG. Growth-based viability (GBV) assays show that the colloidally stable EGCG-coated InSe nanosheets adversely impact the bacterial growth of Shewanella oneidensis MR-1, an environmentally relevant Gram-negative bacterium in aqueous media. The impact on bacterial growth is driven by the EGCG coating of the nanosheets. In addition, live/dead assays show insignificant membrane damage of the Shewanella oneidensis MR-1 cells by InSe nanosheets, suggesting a weak association of EGCG-coated nanosheets with the cells. It is likely that the adverse impact of EGCG-coated nanosheets on bacterial growth is the result of increasing local concentration of EGCG either when adsorbed on the nanosheets when the nanosheets interact with the cells, or when desorbed from the EGCG-coated nanosheets to interact with the bacterial cells.
more »
« less
- Award ID(s):
- 2001611
- PAR ID:
- 10473343
- Publisher / Repository:
- Royal Society of Chemistry
- Date Published:
- Journal Name:
- Environmental Science: Nano
- ISSN:
- 2051-8153
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract Extracellular electron transfer (EET) is a critical form of microbial metabolism that enables respiration on a variety of inorganic substrates, including metal oxides. However, quantifying current generated by electroactive bacteria has been predominately limited to biofilms formed on electrodes. To address this, we developed a platform for quantifying EET flux from cell suspensions using aqueous dispersions of infrared plasmonic tin‐doped indium oxide nanocrystals. Tracking the change in optical extinction during electron transfer enabled quantification of current generated by planktonicShewanella oneidensiscultures. Using this method, we differentiated between starved and actively respiring cells, cells of varying genotype, and cells engineered to differentially express a key EET gene using an inducible genetic circuit. Overall, our results validate the utility of colloidally stable plasmonic metal oxide nanocrystals as quantitative biosensors in aqueous environments and contribute to a fundamental understanding of planktonicS. oneidensiselectrophysiology using simplein situspectroscopy.more » « less
-
Engineered nanoparticles are incorporated into numerous emerging technologies because of their unique physical and chemical properties. Many of these properties facilitate novel interactions, including both intentional and accidental effects on biological systems. Silver-containing particles are widely used as antimicrobial agents and recent evidence indicates that bacteria rapidly become resistant to these nanoparticles. Much less studied is the chronic exposure of bacteria to particles that were not designed to interact with microorganisms. For example, previous work has demonstrated that the lithium intercalated battery cathode nanosheet, nickel manganese cobalt oxide (NMC), is cytotoxic and causes a significant delay in growth of Shewanella oneidensis MR-1 upon acute exposure. Here, we report that S. oneidensis MR-1 rapidly adapts to chronic NMC exposure and is subsequently able to survive in much higher concentrations of these particles, providing the first evidence of permanent bacterial resistance following exposure to nanoparticles that were not intended as antibacterial agents. We also found that when NMC-adapted bacteria were subjected to only the metal ions released from this material, their specific growth rates were higher than when exposed to the nanoparticle. As such, we provide here the first demonstration of bacterial resistance to complex metal oxide nanoparticles with an adaptation mechanism that cannot be fully explained by multi-metal adaptation. Importantly, this adaptation persists even after the organism has been grown in pristine media for multiple generations, indicating that S. oneidensis MR-1 has developed permanent resistance to NMC.more » « less
-
Lithium nickel manganese cobalt oxide (Li x Ni y Mn z Co 1−y−z O 2 , 0 < x , y , z < 1, also known as NMC) is a class of cathode materials used in lithium ion batteries. Despite the increasing use of NMC in nanoparticle form for next-generation energy storage applications, the potential environmental impact of released nanoscale NMC is not well characterized. Previously, we showed that the released nickel and cobalt ions from nanoscale Li 1/3 Ni 1/3 Mn 1/3 Co 1/3 O 2 were largely responsible for impacting the growth and survival of the Gram-negative bacterium Shewanella oneidensis MR-1 (M. N. Hang et al. , Chem. Mater. , 2016, 28 , 1092). Here, we show the first steps toward material redesign of NMC to mitigate its biological impact and to determine how the chemical composition of NMC can significantly alter the biological impact on S. oneidensis . We first synthesized NMC with various stoichiometries, with an aim to reduce the Ni and Co content: Li 0.68 Ni 0.31 Mn 0.39 Co 0.30 O 2 , Li 0.61 Ni 0.23 Mn 0.55 Co 0.22 O 2 , and Li 0.52 Ni 0.14 Mn 0.72 Co 0.14 O 2 . Then, S. oneidensis were exposed to 5 mg L −1 of these NMC formulations, and the impact on bacterial oxygen consumption was analyzed. Measurements of the NMC composition, by X-ray photoelectron spectroscopy, and composition of the nanoparticle suspension aqueous phase, by inductively coupled plasma-optical emission spectroscopy, showed the release of Li, Ni, Mn, and Co ions. Bacterial inhibition due to redesigned NMC exposure can be ascribed largely to the impact of ionic metal species released from the NMC, most notably Ni and Co. Tuning the NMC stoichiometry to have increased Mn at the expense of Ni and Co showed lowered, but not completely mitigated, biological impact. This study reveals that the chemical composition of NMC nanomaterials is an important parameter to consider in sustainable material design and usage.more » « less
-
Chloroplast are sites of photosynthesis that have been bioengineered to produce food, biopharmaceuticals, and biomaterials. Current approaches for altering the chloroplast genome rely on inefficient DNA delivery methods, leading to low chloroplast transformation efficiency rates. For algal chloroplasts, there is no modifiable, customizable, and efficient in situ DNA delivery chassis. Herein, we investigated polyethylenimine-coated single-walled carbon nanotubes (PEI-SWCNT) as delivery vehicles for DNA to algal chloroplasts. We examined the impact of PEI-SWCNT charge and PEI polymer size (25k vs 10k) on the uptake into chloroplasts of wildtype and cell wall knockout mutant strains of the green algae Chlamydomonas reinhardtii. To assess the delivery of DNA bound to PEI-SWCNT, we used confocal microscopy and colocalization analysis of chloroplast autofluorescence with fluorophore-labeled single-stranded GT15 DNA. We found that highly charged DNA-PEI25k-SWNCT have a statistically significant higher percentage of DNA colocalization events with algal chloroplasts (22.28% ± 6.42, 1 hr) over 1-3 hours than DNA-PEI10k-SWNCT (7.23% ± 0.68, 1 hr) (P<0.01). We determined the biocompatibility of DNA-PEI-SWCNT through assays for living algae cells, reactive oxygen species (ROS) generation, and in vivo chlorophyll assays. Through these assays, it was shown that algae exposed to DNA-PEI25k-SWCNT (30 fg/cell) and DNA-PEI10k-SWCNT (300 fg/cell) were viable over 4 days and had little impact on oxidative stress levels. DNA coated PEI-SWCNT transiently increased ROS levels within one hour of exposure to nanomaterials (30- 300 fg/cell) both in the wildtype strain and cell-wall knockout strain, followed by ROS decline to normal levels due to reaction with antioxidant glutathione and lipid membranes. PEI-SWCNT can act as biological carriers for delivering biomolecules such as DNA and have the potential to become novel tools for chloroplast biotechnology and synthetic biology.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/D3EN00382E
