Antibodies under pressure: A Small-Angle X-ray Scattering study of Immunoglobulin G under high hydrostatic pressure.

In the present work two subclasses of the human antibody Immunoglobulin G (IgG) have been investigated by Small-Angle X-ray Scattering under high hydrostatic pressures up to 5kbar. It is shown that IgG adopts a symmetric T-shape in solution which differs significantly from available crystal structures. Moreover, high-pressure experiments verify the high stability of the IgG molecule. It is not unfolded by hydrostatic pressures of up to 5kbar but a slight increase of the radius of gyration was observed at elevated pressures.

Interaction of differently functionalized fluorescent silica nanoparticles with neural stem- and tissue-type cells.

Engineered amorphous silica nanoparticles (SiO2 NPs), due to simple and low cost production, are increasingly used in commercial products and produced on an industrial scale. Despite the potential benefits, there is a concern that exposure to certain types of SiO2 NPs may lead to adverse health effects. As some NPs can cross the blood--brain barrier and may, in addition, reach the central nervous system through the nasal epithelium, this study addresses the responses of different neural tissue-type cells including neural stem cells, neurons, astrocytes and microglia cells to increasing doses of 50 nm fluorescent core/shell SiO2 NPs with different [-NH2, -SH and polyvinylpyrrolidone (PVP)] surface chemistry. The SiO2 NPs are characterized using a variety of physicochemical methods. Assays of cytotoxicity and cellular metabolism indicates that SiO2 NPs cause cell death only at high particle doses, except PVP-coated SiO2 NPs which do not harm cells even at very high concentrations. All SiO2 NPs, except those coated with PVP, form large agglomerates in physiological solutions and adsorb a variety of proteins. Except PVP-NPs, all SiO2 NPs adhere strongly to cell surfaces, but internalization differs depending on neural cell type. Neural stem cells and astrocytes internalize plain SiO2, SiO2-NH2 and SiO2-SH NPs, while neurons do not take up any NPs. The data indicates that the PVP coat, by lowering the particle-biomolecular component interactions, reduces the biological effects of SiO2 NPs on the investigated neural cells.

Altered characteristics of silica nanoparticles in bovine and human serum: the importance of nanomaterial characterization prior to its toxicological evaluation.

BACKGROUND: Many toxicological studies on silica nanoparticles (NPs) have been reported, however, the literature often shows various conclusions concerning the same material. This is mainly due to a lack of sufficient NPs characterization as synthesized as well as in operando. Many characteristics of NPs may be affected by the chemistry of their surroundings and the presence of inorganic and biological moieties. Consequently, understanding the behavior of NPs at the time of toxicological assay may play a crucial role in the interpretation of its results.The present study examines changes in properties of differently functionalized fluorescent 50 nm silica NPs in a variety of environments and assesses their ability to absorb proteins from cell culture medium containing either bovine or human serum. METHODS: The colloidal stability depending on surface functionalization of NPs, their concentration and time of exposure was investigated in water, standard biological buffers, and cell culture media by dynamic light scattering (DLS), zeta potential measurements and transmission electron microscopy (TEM). Interactions of the particles with biological media were investigated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) in bovine and human serum, and extracted proteins were assessed using matrix-assisted laser desorption/ionization-time of flight technique (MALDI-TOF). RESULTS: It was recognized that all of the studied silica NPs tended to agglomerate after relatively short time in buffers and biological media. The agglomeration depended not only on the NPs functionalization but also on their concentration and the incubation time. Agglomeration was much diminished in a medium containing serum. The protein corona formation depended on time and functionalization of NP, and varied significantly in different types of serum. CONCLUSIONS: Surface charge, ionic strength and biological molecules alter the properties of silica NPs and potentially affect their biological effects. The NPs surface in bovine serum and in human serum varies significantly, and it changes with incubation time. Consequently, the human serum, rather than the animal serum, should be used while conducting in vitro or in vivo studies concerning humans. Moreover, there is a need to pre-incubate NPs in the serum to control the composition of the bio-nano-composite that would be present in the human body.

Toward advancing nano-object count metrology: a best practice framework.

BACKGROUND: A movement among international agencies and policy makers to classify industrial materials by their number content of sub-100-nm particles could have broad implications for the development of sustainable nanotechnologies. OBJECTIVES: Here we highlight current particle size metrology challenges faced by the chemical industry due to these emerging number percent content thresholds, provide a suggested best-practice framework for nano-object identification, and identify research needs as a path forward. DISCUSSION: Harmonized methods for identifying nanomaterials by size and count for many real-world samples do not currently exist. Although particle size remains the sole discriminating factor for classifying a material as "nano," inconsistencies in size metrology will continue to confound policy and decision making. Moreover, there are concerns that the casting of a wide net with still-unproven metrology methods may stifle the development and judicious implementation of sustainable nanotechnologies. Based on the current state of the art, we propose a tiered approach for evaluating materials. To enable future risk-based refinements of these emerging definitions, we recommend that this framework also be considered in environmental and human health research involving the implications of nanomaterials. CONCLUSION: Substantial scientific scrutiny is needed in the area of nanomaterial metrology to establish best practices and to develop suitable methods before implementing definitions based solely on number percent nano-object content for regulatory purposes. Strong cooperation between industry, academia, and research institutions will be required to fully develop and implement detailed frameworks for nanomaterial identification with respect to emerging count-based metrics.

Cytotoxicity screening of 23 engineered nanomaterials using a test matrix of ten cell lines and three different assays.

BACKGROUND: Engineered nanomaterials display unique properties that may have impact on human health, and thus require a reliable evaluation of their potential toxicity. Here, we performed a standardized in vitro screening of 23 engineered nanomaterials. We thoroughly characterized the physicochemical properties of the nanomaterials and adapted three classical in vitro toxicity assays to eliminate nanomaterial interference. Nanomaterial toxicity was assessed in ten representative cell lines. RESULTS: Six nanomaterials induced oxidative cell stress while only a single nanomaterial reduced cellular metabolic activity and none of the particles affected cell viability. Results from heterogeneous and chemically identical particles suggested that surface chemistry, surface coating and chemical composition are likely determinants of nanomaterial toxicity. Individual cell lines differed significantly in their response, dependent on the particle type and the toxicity endpoint measured. CONCLUSION: In vitro toxicity of the analyzed engineered nanomaterials cannot be attributed to a defined physicochemical property. Therefore, the accurate identification of nanomaterial cytotoxicity requires a matrix based on a set of sensitive cell lines and in vitro assays measuring different cytotoxicity endpoints.

A reversibly switching block copolymer surface.

We present linear (AB)(n)() multiblock copolymers that exhibit a thermally induced reversible alteration of the surface composition at a sharply defined transition temperature T(s) of 120-170 degrees C depending on the polymer structure. At temperatures below T(s) the surface consists of block A, a 4,4'-methylenediphenyl diisocyanate (4,4'-MDI) type polyurea, whereas above T(s) the hydrophobic block B, a poly(ricinoleic acid hexanediol ester) dominates the surface composition. The ratio of surface concentrations c(A)/c(B) changes by a factor of at least 1000 within an analyzed depth of approximately 10 A. The full A-B surface transition is obtained within minutes. A mechanism is proposed where microphase crystallization of block A in the bulk effectively locks surface segregation of the hydrophobic block B, yielding an A-rich surface. The topology of the copolymers imposes sufficient restrictions for the lateral separation of the connected constituents such that surface segregation is largely reduced. Only above the transition temperature T(s) of microphase crystallization of block A can block B segregate to the surface, yielding a B-rich surface. Such a scheme of competing self-organizing processes in copolymers may potentially be used to reversibly switch surface properties such as adhesion and wetting in various applications.