Methods for the Characterization of the Colloidal Properties of Bacterial Membrane Vesicles.

Bacterial membrane vesicles (BMVs) are extracellular vesicles secreted by either Gram-positive or Gram-negative bacteria. These BMVs typically possess a diameter between 20 and 250 nm. Due to their size, when these BMVs are suspended in another medium, they could be constituents of a colloidal system. It has been hypothesized that investigating BMVs as colloidal particles could help characterize BMV interactions with other environmentally relevant surfaces. Developing a more thorough understanding of BMV interactions with other surfaces would be critical for developing predictive models of their environmental fate. However, this bio-colloidal perspective has been largely overlooked for BMVs, despite the wealth of methods and expertise available to characterize colloidal particles. A particular strength of taking a more colloid-centric approach to BMV characterization is the potential to quantify a particle's attachment efficiency (α). These values describe the likelihood of attachment during particle-particle or particle-surface interactions, especially those interactions which are governed by physicochemical interactions (such as those described by DLVO and xDLVO theory). Elucidating the influence of physical and electrochemical properties on these attachment efficiency values could give insights into the primary factors driving interactions between BMVs and other surfaces. This chapter details methods for the characterization of BMVs as colloids, beginning with size and surface charge (i.e., electrophoretic mobility/zeta potential) measurements. Afterward, this chapter will address experimental design, especially column experiments, targeted for BMV investigation and the determination of α values.

Investigating the use of CaCO3 particles synthesized in the Ca(OH)2-CO2-H2O system for organic matter removal: adsorption efficiency and recyclability.

In this study, we experimentally investigate the production and characterization of CaCO3 particles through the carbonation process of Ca(OH)2 and evaluate their potential application in removing organic matter. The CaCO3 particles were characterized using BET, SEM-EDX, FT-IR, particle size, and XRD techniques. Adsorption of organic matter was studied using synthetic solutions and samples from two surface water sources. Experiments were conducted at room temperature with adsorbent dosages ranging from 1.3 to 21.5 g/L, initial dissolved organic carbon concentrations between 2.5 and 20 mg/L (initial loading: 0.1-14.6 mgDOC/gCaCO3), and a contact time of at least 5 minutes. We observed a removal efficiency of 70-80% for DOC and 90-95% for UV254 at a low concentration of organic matter (humic acids, 2.5 mgDOC/L). At a concentration of 5.0 mg DOC/L, we achieved (i) 70-90% DOC removal for humic acid, (ii) 50-65% DOC removal for one surface water sample with SUVA254 of 2.4 L/mg·m, and (iii) 20-35% DOC removal for another surface water sample with SUVA254 of 4.3 L/mg·m. Furthermore, we investigated the performance of the prepared particles in repeated usage for organics removal. In conclusion, our findings propose areas for future research including optimizing particle cycling within the reaction environment, exploring particle utilization in reactors such as an up-flow particle bed, and assessing potential applications in a membrane contactor. The environmentally friendly and non-toxic nature of CaCO3 particles emphasizes their significance in future research and applications.

Knowledge and Instance Mapping: architecture for premeditated interoperability of disparate data for materials.

Predicting and elucidating the impacts of materials on human health and the environment is an unending task that has taken on special significance in the context of nanomaterials research over the last two decades. The properties of materials in environmental and physiological media are dynamic, reflecting the complex interactions between materials and these media. This dynamic behavior requires special consideration in the design of databases and data curation that allow for subsequent comparability and interrogation of the data from potentially diverse sources. We present two data processing methods that can be integrated into the experimental process to encourage pre-mediated interoperability of disparate material data: Knowledge Mapping and Instance Mapping. Originally developed as a framework for the NanoInformatics Knowledge Commons (NIKC) database, this architecture and associated methods can be used independently of the NIKC and applied across multiple subfields of nanotechnology and material science.

Extracellular Vesicles and Bacteriophages: New Directions in Environmental Biocolloid Research.

There is a long-standing appreciation among environmental engineers and scientists regarding the importance of biologically derived colloidal particles and their environmental fate. This interest has been recently renewed in considering bacteriophages and extracellular vesicles, which are each poised to offer engineers unique insights into fundamental aspects of environmental microbiology and novel approaches for engineering applications, including advances in wastewater treatment and sustainable agricultural practices. Challenges persist due to our limited understanding of interactions between these nanoscale particles with unique surface properties and their local environments. This review considers these biological particles through the lens of colloid science with attention given to their environmental impact and surface properties. We discuss methods developed for the study of inert (nonbiological) particle-particle interactions and the potential to use these to advance our understanding of the environmental fate and transport of extracellular vesicles and bacteriophages.

Characterizing the Transport and Surface Affinity of Extracellular Vesicles Isolated from Yeast and Bacteria in Well-Characterized Porous Media.

Extracellular vesicles (EVs) are membrane-bounded, nanosized particles, produced and secreted by all biological cell types. EVs are ubiquitous in the environment, operating in various roles including intercellular communication and plant immune modulation. Despite their ubiquity, the role of EV surface chemistry in determining transport has been minimally investigated. Using the zeta (ζ)-potential as a surrogate for surface charge, this work considers the deposition of EVs from the yeast, Saccharomyces cerevisiae, and two bacterial species, Staphylococcus aureus and Pseudomonas fluorescens, in well-characterized porous medium under various background conditions shown to influence the transport of other environmental colloidal particles: ionic strength and humic acid concentration. The affinity of S. cerevisiae EVs for the porous medium (glass beads) appeared to be sensitive to changes in ionic strength, as predicted by colloid stability (Derjaguin, Landau, Verwey, and Overbeek or DLVO) theory, and humic acid concentration, while P. fluorescens EVs deviated from DLVO predictions, suggesting that mechanisms other than charge stabilization may control the deposition of P. fluorescens. Calculations of attachment efficiency from these deposition studies were used to estimate EV transport using a clean-bed filtration model. Based on these calculations, EVs could be transported through such homogeneous porous media up to 15 m.

Comparative electrokinetic properties of extracellular vesicles produced by yeast and bacteria.

Extracellular vesicles (EVs) are nano-sized, biocolloidal proteoliposomes that have been shown to be produced by all cell types studied to date and are ubiquitous in the environment. Extensive literature on colloidal particles has demonstrated the implications of surface chemistry on transport behavior. Hence, one may anticipate that physicochemical properties of EVs, particularly surface charge-associated properties, may influence EV transport and specificity of interactions with surfaces. Here we compare the surface chemistry of EVs as expressed by zeta potential (calculated from electrophoretic mobility measurements). The zeta potentials of EVs produced by Pseudomonas fluorescens, Staphylococcus aureus, and Saccharomyces cerevisiae were largely unaffected by changes in ionic strength and electrolyte type, but were affected by changes in pH. The addition of humic acid altered the calculated zeta potential of the EVs, especially for those from S. cerevisiae. Differences in zeta potential were compared between EVs and their respective parent cell with no consistent trend emerging; however, significant differences were discovered between the different cell types and their EVs. These findings imply that, while EV surface charge (as estimated from zeta potential) is relatively insensitive to the evaluated environmental conditions, EVs from different organisms can differ regarding which conditions will cause colloidal instability.

Bringing sex toys out of the dark: exploring unmitigated risks.

A majority of American adults report having used sex toys, which, by design, interact with intimate and permeable body parts yet have not been subject to sufficient risk assessment or management. Physical and chemical data are presented examining potential risks associated with four types of currently available sex toys: anal toy, beads, dual vibrator, and external vibrator. A standardized abrasion machine made real-time breakdown of products into microplastics and nanoplastics. The microplastics from the sex toys were then solvent extracted and analyzed using GC-MS. Rates of microplastics and nanoplastics released during abrasion testing from most microplastic release to least was the anal toy, beads, dual vibrator, external vibrator. Both micro- and nanoplastics particles were generated following the abrasion test, with the 50 percentile diameters (D50) ranging from the anal beads at 658.5 µm, dual vibrator at 887.83 µm, anal toy at 950 µm, and external vibrator at 1673.33 µm. The material matrix of each product was analyzed using ATR-FTIR, with results identifying the anal toy as polyethylene terephthalate (PET), the anal beads as polyvinyl chloride (PVC), the external vibrator as a silicone blend (polydimethylsiloxane [PDMS]), and the dual vibrator as a rubber mixture (polyisoprene). After extraction, phthalates known to be endocrine disruptors were present in all tested sex toys at levels exceeding hazard warnings. Analogous findings have been reported for similar materials that, when incorporated into other product categories, are subject to regulatory scrutiny in both the US and EU. This data set is not intended to be representative of sex toys as an entire class of products, nor are the abrasion experiments claiming to simulate exact use conditions. However, these exploratory data frame potential concerns, highlighting research questions and the need for prompt prioritization of protective action. Therefore, future studies and multi-stakeholder action are needed to understand and reduce risk for this class of products. Supplementary Information: The online version contains supplementary material available at 10.1186/s43591-023-00054-6.

Investigating and Modeling the Regulation of Extracellular Antibiotic Resistance Gene Bioavailability by Naturally Occurring Nanoparticles.

Extracellular antibiotic resistance genes (eARGs) are widespread in the environment and can genetically transform bacteria. This work examined the role of environmentally relevant nanoparticles (NPs) in regulating eARG bioavailability. eARGs extracted from antibiotic-resistant B. subtilis were incubated with nonresistant recipient B. subtilis cells. In the mixture, particle type (either humic acid coated nanoparticles (HASNPs) or their micron-sized counterpart (HASPs)), DNase I concentration, and eARG type were systematically varied. Transformants were counted on selective media. Particles decreased bacterial growth and eARG bioavailability in systems without nuclease. When DNase I was present (≥5 µg/mL), particles increased transformation via chromosomal (but not plasmid-borne) eARGs. HASNPs increased transformation more than HASPs, indicating that the smaller nanoparticle with greater surface area per volume is more effective in increasing eARG bioavailability. These results were also modeled via particle aggregation theory, which represented eARG-bacteria interactions as transport leading to collision, followed by attachment. Using attachment efficiency as a fitting factor, the model predicted transformant concentrations within 35% of experimental data. These results confirm the ability of NPs to increase eARG bioavailability and suggest that particle aggregation theory may be a simplified and suitable framework to broadly predict eARG uptake.

Relationship between Atomic Force Microscopy and Centrifugation Measurements for Dust Fractions Implicated in Solar Panel Soiling.

This work tests the reliability of a simple, rapid centrifugal technique to estimate the removal force necessary to detach common airborne particles from the surface of a photovoltaic panel. Previously, we have used atomic force microscopy (AFM) to obtain the surface-particle adhesion force for different pollutant types that generally contribute to panel soiling. To overcome the limitations of AFM, the same particles were studied as a population using an ultracentrifuge. Detachment was quantified at speeds between 1000 and 10,000 rpm, both as individual particle counts and as projected surface area coverage. The force of centrifugal detachment for each particle type followed a similar trend as the adhesion force given by AFM. Organic and carbon-based materials needed higher centrifugal speeds to be removed, suggesting a stronger attachment to the surface. However, the technique also highlighted the importance of particle diameter, aggregates, and individual particle characteristics, which should be considered when predicting the probability of detachment. We have identified the relationship between AFM-derived adhesion and centrifugal detachment forces using model particle fractions of materials commonly found to soil solar panels, demonstrating the utility in using the more easily applied to centrifugal method to obtain information that can be calibrated to direct measurements of the force of particle attachment. This technique could be applied effectively in further studies on the influence of dust composition on long-term soiling and its reversibility.

Predicting emerging chemical content in consumer products using machine learning.

Chemical ingredients in consumer products are continually changing. To understand our exposure to chemicals and their consequent risk, we need to know their concentrations in products, or chemical weight fractions. Unfortunately, manufacturers rarely report comprehensive weight fraction data on product labels. The goal of this study was to evaluate the utility of machine learning strategies for predicting weight fractions when chemical constituent data are limited. A "data-poor" framework was developed and tested using a small dataset on consumer products containing engineered nanomaterials to represent emerging substances. A second, more traditional framework was applied to a "data-rich" product dataset comprised of bulk-scale organic chemicals for comparison purposes. Feature variables included chemical properties, functional use categories (e.g., antimicrobial), product categories (e.g., makeup), product matrix categories, and whether weight fractions were manufacturer-reported or experimentally obtained. Classification into three weight fraction bins was done using a random forest or nonlinear support vector classifier. An ablation study revealed that functional use data improved predictive performance when included alongside chemical property data, suggesting the utility of functional use categories in evaluating the safety and sustainability of emerging chemicals. Models could roughly stratify material-product observations into order of magnitude weight fractions with moderate success; the best of these achieved an average balanced accuracy of 73% on the nanomaterials product data. Framework comparisons also revealed a positive trend in sample size versus average balanced accuracy, suggesting great promise for machine learning approaches with continued investment in chemical data collection.

Exploring the design implications of bacteriophages in mixed suspensions by considering attachment and break-up.

The validity and usefulness of implementing bacteriophages into water treatment systems as agents of targeted bacterial inactivation is yet to be determined. While some concerns are still more purely biological in nature other concerns are still chiefly rooted in design feasibility. This work investigated bacteriophage heteroaggregation, a process whereby phages attach to non-host background particles, to explore different design options for water quality engineers, especially tuning mixing velocity. This was done by adapting batch/mixing assays, originally developed to study inert particle heteroaggregation, to characterize bacteriophage and kaolinite heteroaggregation using modified Smoluchowski parameters under different ionic strength conditions. This work found that regardless of the ionic strength or the tested phage to kaolinite ratios heteroaggregation occurred rapidly and was likely driven by extended DLVO forces. A model of bacteriophage-kaolinite heteroaggregation was generated and showed promising correspondence with observed laboratory data. This model, along with other findings, suggests that should bacteriophages be utilized as agents of host inactivation they ought to be used following particle separation processes to reduce the likelihood of phage scavenging through attachment to particulate matter rather than the targeted bacteria.

In Vivo Effects of Silver Nanoparticles on Development, Behavior, and Mitochondrial Function are Altered by Genetic Defects in Mitochondrial Dynamics.

Silver nanoparticles (AgNPs) are extensively used in consumer products and biomedical applications, thus guaranteeing both environmental and human exposures. Despite extensive research addressing AgNP safety, there are still major knowledge gaps regarding AgNP toxicity mechanisms, particularly in whole organisms. Mitochondrial dysfunction is frequently described as an important cytotoxicity mechanism for AgNPs; however, it is still unclear if mitochondria are the direct targets of AgNPs. To test this, we exposed the nematodeCaenorhabditis elegans to sublethal concentrations of AgNPs and assessed specific mitochondrial parameters as well as organismal-level endpoints that are highly reliant on mitochondrial function, such as development and chemotaxis behavior. All AgNPs tested significantly delayed nematode development, disrupted mitochondrial bioenergetics, and blocked chemotaxis. However, silver was not preferentially accumulated in mitochondria, indicating that these effects are likely not due to direct mitochondria-AgNP interactions. Mutant nematodes with deficiencies in mitochondrial dynamics displayed both greater and decreased susceptibility to AgNPs compared to wild-type nematodes, which was dependent on the assay and AgNP type. Our study suggests that AgNPs indirectly promote mitochondrial dysfunction, leading to adverse outcomes at the organismal level, and reveals a role of gene-environment interactions in the susceptibility to AgNPs. Finally, we propose a novel hypothetical adverse outcome pathway for AgNP effects to guide future research.

A holistic approach for the recovery of rare earth elements and scandium from secondary sources under a circular economy framework - A review.

Limited natural resources and a continuous increase in the demand for modern technological products, is creating a demand and supply gap for rare earth elements (REEs) and Sc. There is therefore a need to adopt the sustainable approach of the circular economy system (CE). In this review, we defined six steps required to close the loop and recover REEs, using a holistic approach. Recent statistics on REEs and Sc demand and the number of waste generations are reported and studies on more environmentally friendly, economic, and/or efficient recovery processes are summarized. Pilot-scale recovery facilities are described for several types of secondary sources. Finally, we identify obstacles to closing the REE loop in a circular economy and the reasons why secondary sources are not preferred over primary sources. Briefly, recovery from secondary sources should be environmentally and economically friendly and of an acceptable standard concerning final product quality. However, current technologies for recovery from for secondary sources are limiting and technology needs will vary depending on the source type. The quality/purity of the recovered metals should be proven so that they do not result in any adverse effects on the product quality, when they are being used as secondary raw material. In addition, for industrial-scale facilities, process improvements are required that consider environmental conditions.

From bottle to microplastics: Can we estimate how our plastic products are breaking down?

Microplastics (MPs) have become an emerging new pollutant of rising concern due to the exponential growth of plastics in consumer products. Most MP and nanoplastic pollution comes from the fragmentation of plastics through mechanical stress, chemical reactions and biological degradation that occurs during use and after disposal. Models predicting the generation and behavior of MP in the environment are developing, however there is lack of data to predict the rates of MP generation as a function of the abrasive forces. A method to deliver scalable, quantitative release rates of MPs during mechanical stress throughout a plastic's life cycle (e.g., sanding, chewing, river and ocean disposal) is described. A custom abrasion machine was built with features to provide data to calculate power input. The generation rate of MPs through abrasion was tested for the following 3D printed polymers: polylactic acid (PLA), polycarbonate (PC), thermoplastic polyurethane 85A (TPU), polyethylene glycol terephthalate (PETG), high-impact polystyrene (HIPS), and nylon. Each material underwent tensile strength material tests to identify which mechanical properties drive their abrasion rate. Abrasion rate was not observed to correlate to macroscopic mechanic properties. Results indicate that the order of abrasion from most to least were HIPS, nylon, PC, PLA, PETG, and then TPU. This study will help comprehend and provide data to understand generation rates of MPs from consumer plastic products and macro-plastic debris. This will be instrumental in helping to better understand the release of MPs and nanoplastics into the environment and to provide data for fate and transport models, especially in order to predict the amount of plastic entering water systems. MP generation rates and power inputs can be correlated with each plastic's use to inform which release the most MPs and how to better change these products in order to reduce pollution in water sources.

Process optimization for acidic leaching of rare earth elements (REE) from waste electrical and electronic equipment (WEEE).

E-waste (EW) from discarded electrical and electronic devices is a potential source of rare earth elements (REEs) that might be recovered from urban and industrial wastes. REEs are essential raw materials for emerging and high technologies. China currently dominates global REE production with a proportion of 97%. To increase the independence of REE supply and eliminate the environmental impacts related to REE mining, methods for an efficient REE recovery from secondary sources like EW are needed. In this work, we examine improvements in pre-treatment and acidic leaching processes to recover REEs and other valuable metals. EW was crushed and ground prior to the sieving. The materials obtained were then subjected to acid leaching. The parameters used to optimize the conditions for leaching were as follows: acid type (HCl, HNO3, and aqua regia), particle size, and waste-to-acid ratio. The maximum leaching efficiency was obtained from the ground, sieved, and undersized part of e-waste by using HCl with a W:A of 12.5 mg/mL. The total REE concentration was 435 mg/kg. Several treatment scenarios are identified with promise for improving REE recovery at full scale in EW recovery plants and thereby advancing goals for a sustainable, circular economy.

Separation of rare earth elements from mixed-metal feedstocks by micelle enhanced ultrafiltration with sodium dodecyl sulfate.

Micelle enhanced ultrafiltration (MEUF) is a surfactant-based membrane separation process that may be used to separate target ions from mixed metal aqueous solutions, such as leachates of coal ash and other geological wastewaters. The ability of MEUF to separate rare earth elements (REEs) was evaluated using sodium dodecyl sulfate (SDS) as the sorbent in surfactant micelle phase, which was subsequently separated using ultrafiltration, acidification, and ferricyanide precipitation. Separation experiments were performed with a synthetic coal ash leachate feedstock as an example mixed-metal feedstock. Experiments tested the influence of surfactant concentration, pH, and co-existing competitive ions on REE recoveries, and also tested methods for SDS recovery and reuse. Membrane rejection efficiencies of REEs were 97% and 71% respectively for synthetic and real leachate under optimized operating conditions. A two-step process of precipitation with CaCl2 and Na2CO3 following membrane separation was the best for recovering SDS with a yield of 99.7%.

Lack of Detectable Direct Effects of Silver and Silver Nanoparticles on Mitochondria in Mouse Hepatocytes.

Silver nanoparticles (AgNPs) are well-proven antimicrobial nanomaterials, yet little is elucidated regarding the mechanism underlying cytotoxicity induced by these nanoparticles. Here, we tested the hypothesis that mitochondria are primary intracellular targets of two AgNPs and silver ions in mouse hepatocytes (AML12) cultured in glucose- and galactose-based media. AML12 cells were more sensitive to mitochondrial uncoupling when grown with galactose rather than glucose. However, 24 h treatments with 15 nm AgNPs and 6 nm GA-AgNPs (5 and 10 µg/mL) and AgNO3 (1 and 3 µg/mL), concentrations that resulted in either 10 or 30% cytotoxicity, failed to cause more toxicity to AML12 cells grown on galactose than glucose. Furthermore, colocalization analysis and subcellular Ag quantification did not show any enrichment of silver content in mitochondria in either medium. Finally, the effects of the same exposures on mitochondrial respiration were mild or undetectable, a result inconsistent with mitochondrial toxicity causing cell death. Our results suggest that neither ionic Ag nor the AgNPs that we tested specifically target mitochondria and are inconsistent with mitochondrial dysfunction being the primary cause of cell death after Ag exposure under these conditions.

Quantifying Mechanical Abrasion of MWCNT Nanocomposites Used in 3D Printing: Influence of CNT Content on Abrasion Products and Rate of Microplastic Production.

Manufactured nanomaterials (MNMs) are incorporated as "nanofillers" into consumer products to enhance properties of interest. Multiwalled carbon nanotubes (MWCNTs) are known for their unique properties and have many applications in polymers. However, the release of MWCNTs during the nanoenabled product life cycle is concerning. During the use phase, mechanical stresses can produce fragmented materials containing MNMs. The degree of MNM release, the resulting exposure to these materials, and the potential impacts of their release are active research topics. In this study, we describe methodological improvements to study the abrasion of plastics containing MNMs (nanocomposites) and report on characteristics of abrasion products produced and rates of microplastic production. The abrasion device developed for this work allows for the measurement of power inputs to determine scaled release rates. Abrasion rates for plastics used in 3D printing were found to be 0.27 g/m2/s for the PETG polymer and 0.3 g/m2/s for the 2% MWCNT-PETG nanocomposite. Embedded and protuberant MWCNTs appeared to impact the particle size, shape, hydrophobicity, and surface charge of the microplastics, while the inclusion of MWCNTs had a small effect on microplastic production. Measurements of power input to the abrasion process provided a basis for estimating microplastic production rates for these nanocomposites.

Microbial vesicle-mediated communication: convergence to understand interactions within and between domains of life.

All cells produce extracellular vesicles (EVs). These biological packages contain complex mixtures of molecular cargo and have a variety of functions, including interkingdom communication. Recent discoveries highlight the roles microbial EVs may play in the environment with respect to interactions with plants as well as nutrient cycling. These studies have also identified molecules present within EVs and associated with EV surfaces that contribute to these functions. In parallel, studies of engineered nanomaterials have developed methods to track and model small particle behavior in complex systems and measure the relative importance of various surface features on transport and function. While studies of EV behavior in complex environmental conditions have not yet employed transdisciplinary approaches, it is increasingly clear that expertise from disparate fields will be critical to understand the role of EVs in these systems. Here, we outline how the convergence of biology, soil geochemistry, and colloid science can both develop and address questions surrounding the basic principles governing EV-mediated interkingdom interactions.

Effect of Dust Composition on the Reversibility of Photovoltaic Panel Soiling.

Eight types of common airborne particles were used to investigate whether the composition of dust influences its soiling potential on photovoltaic panels. Chosen model particles were roughly spherical, 10-30 µm in diameter to minimize the differences in size and shape. While the predicted van der Waals forces were lower than the adhesion forces measured with an atomic force microscope (AFM), the adhesion potential as a function of surface energy did follow the theoretical pattern. The organic and carbon-based materials, namely the pollen grains and spherical graphite, exhibited a significantly larger adhesion force to the glass surface, indicating high attachment efficiency. The developed generalized linear model confirmed that the type of material should be included in soiling models as a variable, as it provides information on the likelihood of particles sticking to and remaining on the surface. The adhesion force between soiled particles and the surface can be estimated based on the local ambient dust composition to predict the short-term fate of the depositing particles and develop cleaning schedules and techniques accordingly. The results also highlight the need to study dust composition to understand long-term soiling, where chemical characteristics and changing environmental conditions may lead to cementation.