Engineered Nanoparticles Surface Research Articles

The Uptake of Engineered Nanoparticles by Sludge Particulates

The aim of the study was to understand the removal characteristics of engineered nanoparticles (ENP) from sludge treatment processes in wastewater treatment plants (WWTP). Removal of ENP (TiO2, ZnO) was tested on primary and secondary sludge, using differential sedimentation experiments to quantify the attachment of ENP to sludge particulates. To better understand the attachment characteristics, aquatic conditions such as mixed liquid suspended solid concentration, and Ionic strength of the wastewater, were varied to replicate different field conditions of WWTPs. Results showed different degrees of multilayer attachment to sludge surfaces based on the experimental conditions. To verify the effect of ENP surface characters with the sludge attachment, SiO2, ZnO, and TiO2 were tested, showing SiO2 with the highest amount of attachment regardless of its surface charge. With the variation of sludge concentration, up to four degrees of magnitude in sorption was observed. Salt concentrations also showed high impacts on the sorption, where the sorption is decreased by half when doubling the salt concentration. The findings of the current research may aid in understanding the fate of engineered nanoparticles in wastewater treatment plants.

Pharmacokinetic Analysis of Peptide-Modified Nanoparticles with Engineered Physicochemical Properties in a Mouse Model of Traumatic Brain Injury

Peptides are used to control the pharmacokinetic profiles of nanoparticles due to their ability to influence tissue accumulation and cellular interactions. However, beyond the study of specific peptides, there is a lack of understanding of how peptide physicochemical properties affect nanoparticle pharmacokinetics, particularly in the context of traumatic brain injury (TBI). We engineered nanoparticle surfaces with peptides that possess a range of physicochemical properties and evaluated their distribution after two routes of administration: direct injection into a healthy mouse brain and systemic delivery in a mouse model of TBI. In both administration routes, we found that peptide-modified nanoparticle pharmacokinetics were influenced by the charge characteristics of the peptide. When peptide-modified nanoparticles are delivered directly into the brain, nanoparticles modified with positively charged peptides displayed restricted distribution from the injection site compared to nanoparticles modified with neutral, zwitterionic, or negatively charged peptides. After intravenous administration in a TBI mouse model, positively charged peptide-modified nanoparticles accumulated more in off-target organs, including the heart, lung, and kidneys, than zwitterionic, neutral, or negatively charged peptide-modified nanoparticles. The increase in off-target organ accumulation of positively charged peptide-modified nanoparticles was concomitant with a relative decrease in accumulation in the injured brain compared to zwitterionic, neutral, or negatively charged peptide-modified nanoparticles. Understanding how nanoparticle pharmacokinetics are influenced by the physicochemical properties of peptides presented on the nanoparticle surface is relevant to the development of nanoparticle-based TBI therapeutics and broadly applicable to nanotherapeutic design, including synthetic nanoparticles and viruses.Graphical abstract

Covalently Binding of Bovine Serum Albumin to Unsaturated Poly(Globalide-Co-ε-Caprolactone) Nanoparticles by Thiol-Ene Reactions.

When nanoparticles (NPs) are introduced to a biological fluid, different proteins (and other biomolecules) rapidly get adsorbed onto their surface, forming a protein corona capable of giving to the NPs a new "identity" and determine their biological fate. Protein-nanoparticle conjugation can be used in order to promote specific interactions between living systems and nanocarriers. Non-covalent conjugates are less stable and more susceptible to desorption in biological media, which makes the development of engineered nanoparticle surfaces by covalent attachment an interesting topic. In this work, the surface of poly(globalide-co-ε-caprolactone) (PGlCL) nanoparticles containing double bonds in the main polymer chain is covalently functionalized with bovine serum albumin (BSA) by thiol-ene chemistry, producing conjugates which are resistant to dissociation. The successful formation of the covalent conjugates is confirmed by flow cytometry (FC) and fluorescence correlation spectroscopy (FCS). Transmission electron microscopy (TEM) allows the visualization of the conjugate formation, and the presence of a protein layer surrounding the NPs can be observed. After conjugation with BSA, NPs present reduced cell uptake by HeLa and macrophage RAW264.7 cells, in comparison to uncoated NP. These results demonstrate that it is possible to produce stable conjugates by covalently binding BSA to PGlCL NP through thiol-ene reaction.

Impact of nanoparticle surface charge and phosphate on the uptake of coexisting cerium oxide nanoparticles and cadmium by soybean (Glycine max. (L.) merr.)

Engineered nanoparticles (ENPs) often interact closely with coexisting environmental pollutants; however, the effect of their surface properties on such interactions in a plant system has not been examined. This study investigated the roles of ENP surface charge and growth media chemistry on the mutual effects of cerium oxide nanoparticles (CeO2NPs) and cadmium (Cd) on their plant uptake and accumulation in a hydroponic system. Soybean seedlings were exposed to five nanoparticle/Cd treatments including: 100 mg L−1 CeO2NPs(+); 100 mg L−1 CeO2NPs(−); 100 mg L−1 CeO2NPs(+) + 1 mg L−1 Cd; 100 mg L−1 CeO2NPs(−) + 1 mg L−1 Cd; and 1 mg L−1 Cd only, in the presence or absence of 15 mg L−1 phosphorous in the form of phosphate. After 4 days of exposure, concentrations of Cd and Ce in plant tissues were quantified by inductively coupled plasma-mass spectrometry. Roots exposed to CeO2NPs(+) contained 87% higher Ce than plants exposed to CeO2NPs(−). Phosphate significantly increased the root concentration of Ce by 61% and 66% exposed to CeO2NPs(+) and CeO2NPs(−), respectively. The mutual effect of CeO2NPs and Cd was also affected by phosphate, and the net effect of phosphate depended upon the surface charge of CeO2NPs.

Coating aerosolized nanoparticles with low-volatile organic compound (LVOC) vapors modifies surface functionality and oxidative reactivity

Engineered nanoparticles (ENPs) released into the environment have a high probability of interacting with other pollutants before human exposure. These interactions can modify the physicochemical characteristics of ENPs' surface functionality. The toxicity of ENPs can thus largely depend on the coatings picked up in the environment rather than particle core alone. We built a dynamic system to simulate this barely-studied scenario and open up a novel and convenient way to form hydrophobic coatings directly on airborne ENPs. We coated airborne ENPs with low-volatile organic compounds (LVOCs)—common pollutants that exhibit a high affinity for surfaces. Measurement of airborne particle size distribution showed an increase in particle size after coating. The coating thickness was adjustable by controlling the parameters of LVOC generator, namely the reaction temperature and the flow rate through LVOC reservoir, to create 5–90 nm coatings. Transmission electron microscopy images and nanotracking analyses of ENPs suspended in liquid were used to further characterize the coating thickness. Both methods suggested that the system yielded stable, replicable, and well controlled surface coatings. ROS generation of the coated ENPs significantly depended on the type and thickness of LVOC coating. Chemically non-reactive coatings led to significantly reduced ROS generation of silver-ENPs with a 20 nm inert coating quenching close to 100% of ROS generation; this was attributed to the blocked reactive zones on the ENP surfaces. Chemically reactive anthracene coatings, in contrast, first passivated the surface but then contributed to the redox cycle, leading to an increased generation of ROS, which was at a 90 nm coating thickness comparable to that of bare ENPs. Our results add to the understanding of ENP surface functionality—an important aspect of nanotoxicity. Furthermore, the high controllability of our ENP coating system makes it useful for other applications in inducing hydrophobic coating on airborne ENPs.

Modulation of Immune Response Using Engineered Nanoparticle Surfaces.

Nanoparticles (NPs) coated with a monolayer of ligands can be recognized by different components of the immune system, opening new doors for the modulation of immunological responses. By the use of different physical or chemical properties at the NP surface (such as charge, functional groups, and ligand density), NPs can be designed to have distinct cellular uptake, cytokine secretion, and immunogenicity, factors that influence the distribution and clearance of these particles. Understanding these immunological responses is critical for the development of new NP-based carriers for the delivery of therapeutic molecules, and as such several studies have been performed to understand the relationships between immune responses and NP surface functionality. In this review, we will discuss recent reports of these structure-activity relationships, and explore how these motifs can be controlled to elicit therapeutically useful immune responses.

Preferential interaction of Na+ over K+ with carboxylate-functionalized silver nanoparticles

Elucidating mechanistic interactions between monovalent cations (Na+/K+) and engineered nanoparticle surfaces to alter particle stability in polar media have received little attention. We investigated relative preferential interaction of Na+ and K+ with carboxylate-functionalized silver nanoparticles (carboxylate–AgNPs) to determine if interaction preference followed the Hofmeister series (Na+>K+). We hypothesized that Na+ will show greater affinity than K+ to pair with carboxylates on AgNP surfaces, thereby destabilizing the colloidal system. Destabilization upon Na+ or K+ interacting with carboxylate–AgNPs was evaluated probing changes in multiple physicochemical characteristics: surface plasmon resonance/optical absorbance, electrical conductivity, pH, hydrodynamic diameter, electrophoretic mobility, surface charge, amount of Na+/K+ directly associated with AgNPs, and Ag+ dissociation kinetics. We show that Na+ and K+ react differently, indicating local Na+ pairing with carboxylates on AgNP surfaces is kinetically faster and remarkably favored over K+, thus supporting Hofmeister ordering. Our results suggest that AgNPs may transform into micron-size aggregates upon release into aqueous environments and that the fate of such aggregates may need consideration when assessing environmental risk.

Health impact and toxicological effects of nanomaterials in the lung

The manufacture, use and disposal of nanomaterials will result in increased human exposures to engineered nanoparticles (ENPs), potentially via the lung. ENPs differ physically and chemically from natural- or combustion-derived nanoparticles (NP) in important respects. While there are parallels with ultrafine aerosol particles in the atmosphere and colloids in water, there remain some unique issues and impacts of engineered materials on lung health that require consideration and urgent study. The study of toxicity of nanomaterials in biological systems--nanotoxicology--emerged from the observed effects of inhaled particulate matter (PM) and NP. Some engineered nanomaterials deserve special toxicological examination because of their unique properties in biological systems; novel toxicological approaches may be required for their assessment. Translocation in biological systems--a key feature of ENPs--is dependent on ENP size and surface interactions with macromolecules at the portal of entry, upstream of cellular interaction. Of particular significance is the agglomeration processes associated with macromolecule adsorption at ENP surfaces, which determine clearance rates and cellular response. ENP toxicity is therefore dominated by three linked physico-chemical factors: size-shape, surface and 'corona' (formed by adhering macromolecules from the suscipient host). Measuring and predicting ENP translocation and effects following lung entry have proven to be particularly challenging, but understanding ENP behaviour in vivo is fundamental for safe design for effective and targeted drug delivery. Human exposures via medical and dental applications appear important in terms of dose and toxicity, and may need to be assessed for risk on a case-by-case basis.

Responses of Algal Cells to Engineered Nanoparticles Measured as Algal Cell Population, Chlorophyll a, and Lipid Peroxidation: Effect of Particle Size and Type

This paper investigated toxicity of three engineered nanoparticles (ENP), namely, Al2O3, SiO2, and TiO2to the unicellular green algae, exemplified byPseudokirchneriella subcapitatawith an emphasis on particle size. The changes in pH, cell counts, chlorophyll a, and lipid peroxidation were used to measure the responses of the algal species to ENP. The most toxic particle size was TiO2at 42 nm with an EC20 of 5.2 mg/L and Al2O3at 14–18 nm with an EC20 of 5.1 mg/L. SiO2was the least toxic with an EC20 of 318 mg/L. Toxicity was positively related to the surface charge of both ENP and algae. The chlorophyll content of the algal cells was influenced by the presence of ENP, which resulted in limited light and availability of nutrients due to increase in turbidity and nutrient adsorption onto the ENP surface, separately. Lipid peroxidation was attributed to reactive oxygen species (ROS). Fast reaction between algal cells and ROS due to direct contact between TiO2and algal cells is an important factor for lipid peroxidation.

Physicochemical characterization of engineered nanoparticles under physiological conditions: Effect of culture media components and particle surface coating

The use of engineered nanoparticles (ENPs) in commercial products has increased substantially over the last few years. Some research has been conducted in order to determine whether or not such materials are cytotoxic, but questions remain regarding the role that physiological media and sera constituents play in ENP aggregation or stabilization. In this study, several characterization methods were used to evaluate the particle size and surface potential of 6 ENPs suspended in a number of culture media and in the presence of different culture media constituents. Dynamic light scattering (DLS) and fluorescence correlation spectroscopy (FCS) were employed for size determinations. Results were interpreted on the basis of ENP surface potentials evaluated from particle electrophoretic mobilities (EPM). Measurements made after 24 h of incubation at 37 °C showed that the cell culture medium constituents had only moderate impact on the physicochemical properties of the ENP, although incubation in bovine serum albumin destabilized the colloidal system. In contrast, most of the serum proteins increased colloidal stabilization. Moreover, the type of ENP surface modification played a significant role in ENP behavior whereby the complexity of interactions between the ENPs and the medium components generally decreased with increasing complexity of the particle surface. This investigation emphasizes the importance of ENP characterization under conditions that are representative of cell culture media or physiological conditions for improved assessments of nanoparticle cytotoxicity.

Engineered nanoparticle surfaces for improved mass spectrometric analyses

Engineering of nanoparticle surface functionality provides controlled interactions with biomolecules such as cell membrane lipids, proteins and nucleic acids. Concurrently, this surface chemistry control also opens up new avenues for improving mass spectral analyses. In this Minireview, we highlight some of the emerging work that integrates surface-engineered nanoparticles with mass spectrometry to improve the analysis of a wide variety of chemical and biological systems.

Integrated Research Into the Nanoparticle–Protein Corona: A New Focus for Safe, Sustainable and Equitable Development of Nanomedicines

Much contemporary nanotoxicology, nanotherapeutic and nanoregulatory research has been characterized by a focus on investigating how delivery of engineered nanoparticles (ENPs) to cells is dictated primarily by components of the ENP surface. An alternative model, some implications of which are discussed here, begins with fundamental physicochemical research into the interaction of a dynamic nanoparticle-protein corona (NPC) with biological systems. The proposed new model also requires, however, that any such fresh NPC physicochemical research approach should involve integration and targeted collaboration from the earliest stages with nanotoxicology, nanotherapeutics and nanoregulatory expertise. The justification for this integrated approach, we argue, relates not just to efficiency and promotion of innovation but to an acknowledgement that public-funded basic physicochemical research in particular should now be accepted to incorporate strong higher order public-goods elements from its inception, not merely after product development at the technology-transfer stage. Issues, such as university-research cooperation, commercialization and intellectual property protection, safety and cost-effectiveness regulatory assessment, as well as technology transfer should not be viewed as second tier considerations, even in a 'blue sky' NPC basic research agenda.