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Heteroaggregation of multiwalled carbon nanotubes and hematite nanoparticles: rates and mechanisms.

ABSTRACT: The heteroaggregation rates of negatively charged multiwalled carbon nanotubes (CNTs) and positively charged hematite nanoparticles (HemNPs) were obtained over a broad range of nanoparticle distributions using time-resolved dynamic light scattering (DLS). Binary systems comprising CNTs and HemNPs were prepared using low ionic strength solutions to minimize the concurrent occurrence of homoaggregation. To elucidate the mechanisms of heteroaggregation, the structures of CNT-HemNP aggregates were observed using cryogenic transmission electron microscopy (cryo-TEM). An initial increase in the CNT concentration, while keeping the HemNP concentration constant, resulted in a corresponding increase in the rate of heteroaggregation, which occurred through the bridging of HemNPs by CNT strands. At the optimal CNT/HemNP mass concentration ratio (CNT/HemNP ratio) of 0.0316, the heteroaggregation rate reached 3.3 times of the HemNP homoaggregation rate in the diffusion-limited regime. Increasing the CNT/HemNP ratio above the optimal value, however, led to a dramatic decrease in the growth rate of heteroaggregates, likely through a blocking mechanism. In the presence of humic acid, the trends in the variation of the heteroaggregation rate with CNT/HemNP ratio were similar to that in the absence of humic acid. However, as the humic acid concentration was increased, the maximum aggregate growth rate decreased due to the lessening in the available surface of the HemNPs that CNTs can attach to through favorable electrostatic interaction.

SUBMITTER: Huynh KA

PROVIDER: S-EPMC3394682 | biostudies-literature | 2012 Jun

REPOSITORIES: biostudies-literature

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Heteroaggregation of multiwalled carbon nanotubes and hematite nanoparticles: rates and mechanisms.

Huynh Khanh An KA McCaffery J Michael JM Chen Kai Loon KL

Environmental science & technology 20120516 11

The heteroaggregation rates of negatively charged multiwalled carbon nanotubes (CNTs) and positively charged hematite nanoparticles (HemNPs) were obtained over a broad range of nanoparticle distributions using time-resolved dynamic light scattering (DLS). Binary systems comprising CNTs and HemNPs were prepared using low ionic strength solutions to minimize the concurrent occurrence of homoaggregation. To elucidate the mechanisms of heteroaggregation, the structures of CNT-HemNP aggregates were o ...[more]

PMID: 22545989

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Project description:Multiwalled carbon nanotubes (MWCNTs) regularly enter aquatic environments due to their ubiquity in consumer products and engineering applications. However, the effects of MWCNT pollution on the environmental microbiome are poorly understood. Here, we evaluated whether these carbon nanoparticles can elevate the spread of antimicrobial resistance by promoting bacterial plasmid transfer, which has previously been observed for copper nanomaterials with antimicrobial properties as well as for microplastics. Through a combination of experimental liquid mating assays between Pseudomonas putida donor and recipient strains with plasmid pKJK5::gfpmut3b and mathematical modeling, we here demonstrate that the presence of MWCNTs leads to increased plasmid transfer rates in a concentration-dependent manner. The percentage of transconjugants per recipient significantly increased from 0.21 ± 0.04% in absence to 0.41 ± 0.09% at 10 mg L-1 MWCNTs. Similar trends were observed when using an Escherichia coli donor hosting plasmid pB10. The identified mechanism underlying the observed dynamics was the agglomeration of MWCNTs. A significantly increased number of particles with >6 μm diameter was detected in the presence of MWCNTs, which can in turn provide novel surfaces for bacterial interactions between donor and recipient cells after colonization. Fluorescence microscopy confirmed that MWCNT agglomerates were indeed covered in biofilms that contained donor bacteria as well as elevated numbers of green fluorescent transconjugant cells containing the plasmid. Consequently, MWCNTs provide bacteria with novel surfaces for intense cell-to-cell interactions in biofilms and can promote bacterial plasmid transfer, hence potentially elevating the spread of antimicrobial resistance. IMPORTANCE In recent decades, the use of carbon nanoparticles, especially multiwalled carbon nanotubes (MWCNTs), in a variety of products and engineering applications has been growing exponentially. As a result, MWCNT pollution into environmental compartments has been increasing. We here demonstrate that the exposure to MWCNTs can affect bacterial plasmid transfer rates in aquatic environments, an important process connected to the spread of antimicrobial resistance genes in microbial communities. This is mechanistically explained by the ability of MWCNTs to form bigger agglomerates, hence providing novel surfaces for bacterial interactions. Consequently, increasing pollution with MWCNTs has the potential to elevate the ongoing spread of antimicrobial resistance, a major threat to human health in the 21st century.

Dataset Information

Heteroaggregation of multiwalled carbon nanotubes and hematite nanoparticles: rates and mechanisms.

Publications

Heteroaggregation of multiwalled carbon nanotubes and hematite nanoparticles: rates and mechanisms.

Similar Datasets

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