Proteomic characterization of engineered nanomaterial-protein interactions in relation to surface reactivity

Safety assessment of nanomaterials: implications for nanomedicine

Nanotechnologies offer exciting opportunities for targeted drug delivery which is anticipated to increase the efficacy of the drug and reduce potential side-effects, through the reduction of the dose of the drug in bystander tissues and an increase of the drug at the desired target site. Nevertheless, understanding whether the nano-scale carriers themselves may exert adverse effects is of great importance. The small size may enable nanoparticles to negotiate various biological barriers in the body which could, in turn, give rise to unexpected toxicities. On the other hand, the potential of nanoparticles to cross barriers can also be exploited for drug delivery. Determining the fate of nanoparticles following their therapeutic or diagnostic application is critical: are nanoparticles excreted, or biodegraded, or do they accumulate, potentially leading to harmful long-term effects? The bio-corona of proteins or lipids on the surface of nanoparticles is a key parameter for the understanding of biological interactions of nanoparticles. In the present review, we discuss some of the major challenges related to safety of nanomedicines.

Heteroepitaxial streptavidin nanocrystals reveal critical role of proton "fingers" and subsurface atoms in determining adsorbed protein orientation

Characterization of noncovalent interactions between nanometer-sized structures, such as proteins, and solid surfaces is a subject of intense interest of late owing to the rapid development of numerous solid materials for medical and technological applications. Yet the rational design of these surfaces to promote the adsorption of specific nanoscale complexes is hindered by a lack of an understanding of the noncovalent interactions between nanostructures and solid surfaces. Here we take advantage of the unexpected observation of two-dimensional nanocrystals of streptavidin on muscovite mica to provide details of the streptavidin-mica interface. Analysis of atomic force microscopic images together with structural modeling identifies six positively charged residues whose terminal amine locations match the positions of the single atom-sized anionic cavities in the basal mica surface to within 1 Å. Moreover, we find that the streptavidin crystallites are oriented only along a single direction on this surface and not in either of three different directions as they must be if the protein interacted solely with the 3-fold symmetric basal surface atoms. Hence, this broken symmetry indicates that the terminal amine protons must also interact directly with the subsurface hydroxide atoms that line the bottom of these anionic cavities and generate only a single axis of symmetry. Thus, in total, these results reveal that subsurface atoms can have a significant influence on protein adsorption and orientation and identify the insertion of proton "fingers" as a means by which proteins may generally interact with solid surfaces.

Interaction of lipid vesicle with silver nanoparticle-serum albumin protein corona

The physical interaction between a lipid vesicle and a silver nanoparticle (AgNP)-human serum albumin (HSA) protein "corona" has been examined. Specifically, the binding of AgNPs and HSA was analyzed by spectrophotometry, and the induced conformational changes of the HSA were inferred from circular dichroism spectroscopy. The fluidity of the vesicle, a model system for mimicking cell membrane, was found to increase with the increased exposure to AgNP-HSA corona, though less pronounced compared to that induced by AgNPs alone. This study offers additional information for understanding the role of physical forces in nanoparticle-cell interaction and has implications for nanomedicine and nanotoxicology.

Understanding and controlling the interaction of nanomaterials with proteins in a physiological environment

Nanomaterials hold promise as multifunctional diagnostic and therapeutic agents. However, the effective application of nanomaterials is hampered by limited understanding and control over their interactions with complex biological systems. When a nanomaterial enters a physiological environment, it rapidly adsorbs proteins forming what is known as the protein 'corona'. The protein corona alters the size and interfacial composition of a nanomaterial, giving it a biological identity that is distinct from its synthetic identity. The biological identity determines the physiological response including signalling, kinetics, transport, accumulation, and toxicity. The structure and composition of the protein corona depends on the synthetic identity of the nanomaterial (size, shape, and composition), the nature of the physiological environment (blood, interstitial fluid, cell cytoplasm, etc.), and the duration of exposure. In this critical review, we discuss the formation of the protein corona, its structure and composition, and its influence on the physiological response. We also present an 'adsorbome' of 125 plasma proteins that are known to associate with nanomaterials. We further describe how the protein corona is related to the synthetic identity of a nanomaterial, and highlight efforts to control protein-nanomaterial interactions. We conclude by discussing gaps in the understanding of protein-nanomaterial interactions along with strategies to fill them (167 references).

Plant nanotoxicology

The anthropogenic release of nanoparticles (NPs) to the environment poses a potential hazard to human health and life. The interplay between NPs and biological processes is receiving increasing attention. Plants expose huge interfaces to the air and soil environment. Thus, NPs are adsorbed to the plant surfaces, taken up through nano- or micrometer-scale openings of plants and are translocated within the plant body. Persistent NPs associated with plants enter the human food chain. In this Opinion, we document the occurrence and character of NPs in the environment and evaluate the need for future research on toxicological effects. Plant nanotoxicology is introduced as a discipline that explores the effects and toxicity mechanisms of NPs in plants, including transport, surface interactions and material-specific responses.

Long, needle-like carbon nanotubes and asbestos activate the NLRP3 inflammasome through a similar mechanism

Carbon nanomaterials (CNM) are targets of great interest because they have multiple applications in industry but also because of the fear of possible harmful heath effects of certain types of CNM. The high aspect ratio of carbon nanotubes (CNT), a feature they share with asbestos, is likely the key factor for reported toxicity of certain CNT. However, the mechanism to explain this toxicity is unclear. Here we investigated whether different CNM induce a pro-inflammatory response in human primary macrophages. Carbon black, short CNT, long, tangled CNT, long, needle-like CNT, and crocidolite asbestos were used to compare the effect of size and shape on the potency of the materials to induce secretion of interleukin (IL) 1-family cytokines. Our results demonstrated that long, needle-like CNT and asbestos activated secretion of IL-1β from LPS-primed macrophages but only long, needle-like CNT induced IL-1α secretion. SiRNA experiments demonstrated that the NLRP3 inflammasome was essential for long, needle-like CNT and asbestos-induced IL-1β secretion. Moreover, it was noted that CNT-induced NLRP3 inflammasome activation depended on reactive oxygen species (ROS) production, cathepsin B activity, P2X(7) receptor, and Src and Syk tyrosine kinases. These results provide new information about the mechanisms by which long, needle-like materials may cause their harmful health effects. Furthermore, the techniques used here may be of use in future risk assessments of nanomaterials.

The effects of aggregation and protein corona on the cellular internalization of iron oxide nanoparticles

Engineered inorganic nanoparticles are essential components in the development of nanotechnologies. For applications in nanomedicine, particles need to be functionalized to ensure a good dispersibility in biological fluids. In many cases however, functionalization is not sufficient: the particles become either coated by a corona of serum proteins or precipitate out of the solvent. In the present paper, we show that by changing the coating of iron oxide nanoparticles from a low-molecular weight ligand (citrate ions) to small carboxylated polymers (poly(acrylic acid)), the colloidal stability of the dispersion is improved and the adsorption/internalization of iron toward living mammalian cells is profoundly affected. Citrate-coated particles are shown to destabilize in all fetal-calf-serum based physiological conditions tested, whereas the polymer coated particles exhibit an outstanding dispersibility as well as a structure devoid of protein corona. The interactions between nanoparticles and human lymphoblastoid cells are investigated by transmission electron microscopy and flow cytometry. Two types of nanoparticle/cell interactions are underlined. Iron oxides are found either adsorbed on the cellular membranes, or internalized into membrane-bound endocytosis compartments. For the precipitating citrate-coated particles, the kinetics of interactions reveal a massive and rapid adsorption of iron oxide on the cell surfaces. The quantification of the partition between adsorbed and internalized iron was performed from the cytometry data. The results highlight the importance of resilient adsorbed nanomaterials at the cytoplasmic membrane.

Solution-engineered palladium nanoparticles: model for health effect studies of automotive particulate pollution

Palladium (Pd) nanoparticles are recognized as components of airborne automotive pollution produced by abrasion of catalyst materials in the car exhaust system. Here we produced dispersions of hydrophilic spherical Pd nanoparticles (Pd-NP) of uniform shape and size (10.4 ± 2.7 nm) in one step by Bradley's reaction (solvothermal decomposition in an alcohol or ketone solvent) as a model particle for experimental studies of the Pd particles in air pollution. The same approach provided mixtures of Pd-NP and nanoparticles of non-redox-active metal oxides, such as Al(2)O(3). Particle aggregation in applied media was studied by DLS and nanoparticle tracking analysis. The putative health effects of the produced Pd nanoparticles and nanocomposite mixtures were evaluated in vitro, using human primary bronchial epithelial cells (PBEC) and a human alveolar carcinoma cell line (A549). Viability of these cells was tracked by vital dye exclusion, and apoptosis was also assessed. In addition, we monitored the release of IL-8 and PGE(2) in response to noncytotoxic doses of the nanoparticles. Our studies demonstrate cellular uptake of Pd nanoparticles only in PBEC, as determined by TEM, with pronounced and dose-dependent effects on cellular secretion of soluble biomarkers in both cell types and a decreased responsiveness of human epithelial cells to the pro-inflammatory cytokine TNF-α. When cells were incubated with higher doses of the Pd nanoparticles, apoptosis induction and caspase activation were apparent in PBEC but not in A549 cells. These studies demonstrate the feasibility of using engineered Pd nanoparticles to assess the health effects of airborne automotive pollution.