Kevin Powers

Characterization of the size, shape, and state of dispersion of nanoparticles for toxicological studies

This paper describes the issues relating to the measurement of nanoparticle size, shape and dispersion when evaluating the toxicity of nanoparticles. Complete characterization of these materials includes much more than size, size distribution and shape; nonetheless, these attributes are usually the essential foundation. The measurement of particle size, particularly at scales of 100 nm or less, can be challenging under the best of conditions. Measurements that are routine in the laboratory setting become even more difficult when made under the physiological conditions relevant to toxicity studies, where the environment of the particles can be quite complex. Passive and active cellular responses, as well as the presence of a variety of nano-scale biological structures, often complicate the collection and interpretation of size and shape data. In this paper, we highlight several of the common issues faced when characterizing nanoparticles for toxicity testing and suggest general protocols to address these problems.

Influence of Suwannee River humic acid on particle properties and toxicity of silver nanoparticles

Adsorption of natural organic matter (NOM) on nanoparticles can have dramatic impacts on particle dispersion resulting in altered fate and transport as well as bioavailability and toxicity. In this study, the adsorption of Suwannee River humic acid (SRHA) on silver nanoparticles (nano-Ag) was determined and showed a Langmuir adsorption at pH 7 with an adsorption maximum of 28.6 mg g(-1) nano-Ag. It was also revealed that addition of <10 mg L(-1) total organic carbon (TOC) increased the total Ag content suspended in the aquatic system, likely due to increased dispersion. Total silver content decreased with concentrations of NOM greater than 10mg TOCL(-1) indicating an increase in nanoparticle agglomeration and settling above this concentration. However, SRHA did not have any significant effect on the equilibrium concentration of ionic Ag dissolved in solution. Exposure of Daphnia to nano-Ag particles (50 μg L(-1) and pH 7) produced a linear decrease in toxicity with increasing NOM. These results clearly indicate the importance of water chemistry on the fate and toxicity of nanoparticulates.

Differential binding of serum proteins to nanoparticles

In the physiological environment, endogenous proteins readily adsorb to the surface of foreign materials. These proteins facilitate recognition by phagocytic cells and strongly influence the nature of the immune and inflammatory responses. Properly anticipating the potential adverse effects caused by nanomaterials requires a fundamental understanding of the physical properties that govern this process. The large number of adherent proteins and the competitive nature of adsorption in multicomponent solutions have made quantifying protein adsorption to nanomaterials from native physiological fluids a challenging analytical prospect. In this paper, we report the use of an isotope coded affinity tag (ICAT) based dual-label method to identify the proteins that adsorb to aluminium, nickel and diamond nanoparticles following their exposure to human serum. With this method, we were able to identify 69 unique proteins that exhibited adsorption to the various nanoparticles and quantify the relative affinities with which these proteins bind.

Amorphous silica coatings on magnetic nanoparticles enhance stability and reduce toxicity to in vitro BEAS-2B cells

Background: Nanoparticles are being rapidly assimilated into numerous research fields and consumer products. A concurrent increase in human exposure to such materials is expected. Magnetic nanoparticles (MNPs) possess unique and beneficial features, increasing their functionality and integrative potential. However, MNP toxicity characterization is limited, especially in regards to the human respiratory system. This study aimed to assess the in vitro effects of airborne MNPs on BEAS-2B cells. Uncoated iron oxide was compared with two amorphous silica-coated MNPs, hypothesizing the coatings reduced toxicity and increased particle stability. Method: BEAS-2B cells were cultured at an air–liquid interface and exposed to airborne MNPs using a fabricated exposure device. Indices of cytotoxicity, inflammatory response, oxidative stress, and iron homeostasis were monitored postexposure via cell viability assays and qRT-PCR. Concentrations of soluble iron-associated with different MNPs were also examined before and after contact with several aqueous organic and inorganic acids. Results: The silica-coated MNPs had reduced soluble iron concentrations. This result indicates that the silica coating provides a barrier to and prevents the mobilization of soluble iron from the particle to the cell, thereby reducing the risk of oxidative stress or alterations of iron homeostasis. Cells exposed to MagSilica50 and MagSilica50–85® showed little to no indications of cytotoxicity or induction of inflammatory response/oxidative stress at the examined delivery concentrations. Conclusion: MNPs coated with amorphous silica are protected from acidic erosion. Correspondingly, the particle stability translates into reduced cytotoxicity and cellular influence on human airway epithelial cells.

Nanoparticle Characterization for Cancer Nanotechnology and Other Biological Applications

Nanotechnology is actively being used to develop promising diagnostics and therapeutics tools for the treatment of cancer and many other diseases. The unique properties of nanomaterials offer an exciting frontier of possibilities for biomedical researchers and scientists. Because existing knowledge of macroscopic materials does not always allow for adequate prediction of the characteristics and behaviors of nanoscale materials in controlled environments, much less in biological systems, careful nanoparticle characterization should accompany biomedical applications of these materials. Informed correlations between adequately characterized nanomaterial properties and reliable biological endpoints are essential for guiding present and future researchers toward clinical nanotechnology-based solutions for cancer. Biological environments are notoriously dynamic; hence, nanoparticulate interactions within these environments will likely be comparatively diverse. For this reason, we recommend that an interactive and systematic approach to material characterization be taken when attempting to elucidate or measure biological interactions with nanoscale materials. We intend for this chapter to be a practical guide that could be used by researchers to identify key nanomaterial characteristics that require measurement for their systems and the appropriate techniques to perform those measurements. Each section includes a basic overview of each measurement and notes on how to address some of the common difficulties associated with nanomaterial characterization.

Investigation of acute nanoparticulate aluminum toxicity in zebrafish.

In freshwater fish, aluminum is a well‐recognized gill toxicant, although responses are influenced by pH. Aluminum nanomaterials are being used in diverse applications that are likely to lead to environmental release and exposure. However, it is unclear if the effects of nanoparticulate aluminum are similar to those of other forms of aluminum or require special consideration. To examine the acute toxicological effects of exposure to aluminum nanoparticle (Al‐NP)s, adult female zebrafish were exposed to either Al‐NPs or aluminum chloride for up to 48 hours in moderately hard fresh water. Al‐NPs introduced into test water rapidly aggregated and up to 80% sedimented from the water column during exposures. No mortality was caused by concentrations of Al‐NP up to 12.5 mg/L. After exposure, tissue concentrations of aluminum, effects on gill morphology, Na+, K+ ‐ATPase (NKA) activity, and global gene expression patterns were examined. Exposure to both aluminum chloride and nanoparticulate aluminum resulted in a concentration dependent decrease in sodium potassium ATPase activity, although Al‐NP exposure did not alter gill morphology as measured by filament widths. Decreased ATPase activity coincided with decreases in filamental NKA staining and mucous cell counts. Analysis of gill transcriptional responses demonstrated that exposure to 5 mg/L Al‐NP only resulted in significant changes in expression of two genes, whereas aluminum chloride exposure significantly affected the expression of 105 genes. Taken together, these results indicate that nanoparticulate aluminum has little acute toxicity for zebrafish in moderately hard freshwater.

Mesoporous TMOS–MTMS copolymer silica gels catalyzed by fluoride

Abstract Mesoporous HF-catalyzed tetramethoxysilane-methyltrimethoxysilane (TMOS–MTMS) copolymer silica gels with average pore diameter from 80 to 100 A and narrow pore size distribution have been obtained. Mesoporous TMOS–MTMS copolymer gels with tetramethoxysilane ranging from 10% to 100% were also produced with tetrabutylammonium fluoride (TBAF) catalyst. The pore sizes of TBAF-catalyzed copolymer gels were controlled over a range from 25 to 194 A. Their pore sizes increased with increasing fluoride content to R 2 =0.112 ( R 2 , molar ratio of F/Si) and then level off. The catalytic effect of fluoride on the sol–gel process was investigated. The results suggest that multi-fluorinated silicon species catalyze the silica polymerization.

Effect of Y3+, Gd 3+ and La3+ dopant ions on structural, optical and electrical properties of o-mullite nanoparticles

Abstract Dielectric ceramics of M(x)Al6(1–x)Si2O13 doped mullite were synthesized via co-precipitation technique. The X-ray diffraction profiles revealed that these nanoparticles were crystallized well and the volume of mullite unit cell was increased as a function of the ionic radius of dopant ion. TEM images showed regular orthorhombic crystal morphology for the pure mullite sample. Meanwhile, the doped samples exhibited slightly distorted crystal morphology of larger particle sizes. DSC thermograms evinced that the exothermic peak temperature of mullite was shifted to the lower value with M3+ ion insertion. The photoluminescence spectra were studied for mullite samples, and it was found that the intensity of the emission spectra was affected by the M3+ ion type. It was found that, Y3+ doped mullite achieved the minimum dielectric loss value of 0.01 in the radio wave frequency region (1 MHz). Meanwhile, Gd3+ doped mullite achieved the minimum dielectric loss value of 0.09 in the microwave frequency region (1 GHz).

Characterization of Nanomaterials for Toxicological Studies

The scientific community, regulatory agencies, environmentalists, and most industry representatives all agree that more effort is required to ensure the responsible and safe development of new nanotechnologies. Characterizing nanomaterials is a key aspect in this effort. There is no universally agreed upon minimum set of characteristics although certain common properties are included in most recommendations. Therefore, characterization becomes more like a puzzle put together with various measurements rather than a single straightforward analytical measurement. In this chapter, we emphasize and illustrate the important elements of nanoparticle characterization with a systematic approach to physicochemical characterization. We start with an overview describing the properties that are most significant to toxicological testing along with suggested methods for characterizing an as-received nanomaterial and then specifically address the measurement of size, surface properties, and imaging.

Screening Experiments for Removal of Low-Level Tritiated Water

Screening experiments for low levels of tritiated water (HTO) remediation based upon selective adsorption/desorption mechanisms utilizing equilibrium isotope effects have been carried out. Several organic and inorganic high surface area materials were investigated to assess their ability to selectively adsorb low concentrations of HTO. Ion-exchange resins with cation functionalities, chitosan, sodium alginate, and several inorganic media modified with metal cations exhibited promising results. Biomaterials, for example, chitosan and modified alginate, demonstrated positive results. Based on the literature and our preliminary testing, we postulate four possible mechanisms for selected tritium adsorption: hydrogen ion exchange, HTO coordination with surface cation sites, hydrogen bonding to surface basic sites, and secondary hydrogen bonding (structural water) in fine pores.