Lack of hydroxylated fullerene toxicity after intravenous administration to female Sprague-Dawley rats.

Hydroxylated fullerenes (C60OH(x)) or fullerols are water-soluble carbon nanoparticles that have been explored for potential therapeutic applications. This study assesses acute in vivo tolerance in 8-wk-old female Sprague-Dawley rats to intravenous (iv) administration of 10 mg/kg of well-characterized C60(OH)30. Complete histopathology and clinical chemistries are assessed at 8, 24, and 48 h after dosing. Minor histopathology changes are seen, primarily in one animal. No clinically significant chemistry changes were observed after treatment. These experiments suggest that this fullerol was well tolerated after iv administration to rats.

In vitro biodistribution of silver nanoparticles in isolated perfused porcine skin flaps.

Nanomaterials increasingly are playing a role in society for uses ranging from biomedicine to microelectronics; however, pharmacokinetic studies, which will be necessary for human health risk assessments, are limited. Currently the most widely used nanoparticle in consumer products is silver (Ag). The objective of the present study was to quantify the local biodistribution of two types of Ag nanoparticles, Ag-citrate and Ag-silica, in the isolated perfused porcine skin flap (IPPSF). IPPSFs were perfused for 4 h with 0.84 µg ml(-1) Ag-citrate or 0.48 µg ml(-1) Ag-silica followed by a 4-h perfusion with media only during a washout phase. Arterial and venous concentrations of Ag were measured in the media by inductively coupled plasma optical emission spectrometry (ICP-OES). Venous concentrations of Ag for both types of nanoparticles were best fit with a two compartment model. The normalized volumes of distribution estimated from the noncompartmental analysis of the venous concentrations indicated distribution of Ag greater than the vascular space; however, because total Ag was measured, the extravascular distribution could be attributed to diffusion of Ag ions. The estimated clearance for both types of Ag nanoparticles was 1 ml min(-1) , which was equal to the flap perfusion rate, indicating no detectable elimination of Ag from the system. Four hours after infusion of the Ag nanoparticles, the recovery of Ag in the venous effluent was 90 ± 5.0% and 87 ± 22% of the infused Ag for Ag-citrate and Ag-silica, respectively.

Interactions of aluminum nanoparticles with human epidermal keratinocytes.

Aluminum nanoparticles (Al NP) have been used in applications as diverse as drug delivery, material surface coatings and an ingredient for solid rocket fuel in military explosives and artillery. Although Al NP are used in many civilian and military applications, the health and safety implications of these nanosize particles are not known. To understand the interactions and biological activity of Al NP in human cells, cultured human neonatal epidermal keratinocytes (HEK) were exposed for 24 h to 50 and 80 nm Al NP in concentrations from 4.0 to 0.0004 mg ml(-1) to assess the cytotoxicity and inflammatory potential. UV-Vis measurements and nanoparticle controls revealed that the Al NP interact with the assay dyes. Viability did not decrease in HEK exposed to both the 50 and the 80 nm Al NP at all treatment concentrations with MTT, CellTiter 96 AQueous One (96 AQ) and alamar Blue (aB) viability assays. The 96 AQ and aB assays interact with the Al NP less than MTT, and proved to be the best assays to use with these Al NP. TEM depicted Al NP localized within the cytoplasmic vacuoles of the cells. Cytokine data was variable, indicating possible nanoparticle interactions with the cytokine assays. These studies illustrate the difficulties involved in assessing the biological safety of nanomaterials such as Al NP due to media- and temperature-dependent particle agglomeration and nanoparticle interactions with biomarkers of cytotoxicity.

Multi-walled carbon nanotube interactions with human epidermal keratinocytes.

Carbon nanotubes have widespread applications in multiple engineering disciplines. However, little is known about the toxicity or interaction of these particles with cells. Carbon nanotube films were grown using a microwave plasma enhanced chemical vapor deposition system. Human epidermal keratinocytes (HEK) were exposed to 0.1, 0.2, and 0.4 mg/ml of multi-walled carbon nanotubes (MWCNT) for 1, 2, 4, 8, 12, 24 and 48 h. HEK were examined by transmission electron microscopy for the presence of MWCNT. Here we report that chemically unmodified MWCNT were present within cytoplasmic vacuoles of the HEK at all time points. The MWCNT also induced the release of the proinflammatory cytokine interleukin 8 from HEKs in a time dependent manner. These data clearly show that MWCNT, not derivatized nor optimized for biological applications, are capable of both localizing within and initiating an irritation response in a target epithelial cell that composes a primary route of occupational exposure for manufactured nanotubes.

Surfactant effects on carbon nanotube interactions with human keratinocytes.

Interactions of multiwalled carbon nanotubes (MWCNTs) with human epidermal keratinocytes (HEKs) were studied with respect to the effect of surfactant on dispersion of MWCNT aggregates and cytotoxicity. Our earlier studies had shown that the unmodified MWCNTs were localized within the cytoplasmic vacuoles of HEKs and elicited an inflammatory response. However, MWCNTs in solution tend to aggregate and, therefore, cells are exposed to large MWCNT aggregates. The purpose of this study was to find a surfactant that prevents the formation of large aggregates of MWCNTs without being toxic to the HEKs. HEKs were exposed to serial dilutions (10% to 0.1%) of L61, L92, and F127 Pluronic and 20 or 60 Tween for 24 hours. HEK viability, proportional to surfactant concentration, ranged from 27.1% to 98.5% with Pluronic F127; viability with the other surfactants was less than 10%. Surfactants dispersed and reduced MWCNT aggregation in medium. MWCNTs at 0.4 mg/mL in 5% or 1% Pluronic F127 were incubated with HEKs and assayed for interleukin 8 (IL-8). MWCNTs were cytotoxic to HEKs independent of surfactant exposure. In contrast, MWCNT-induced IL-8 release was reduced when exposed to 1% or 5% Pluronic F127 (P < .05). However, both MWCNTs and surfactant, alone or in combination, increased IL-8 release compared with control exposures at 12 and 24 hours. These results suggest that the surfactant-MWCNT interaction is more complex than simple dispersion alone and should be investigated to determine the mode of interaction.

Percutaneous absorption of 2,6-di-tert-butyl-4-nitrophenol (DBNP) in isolated perfused porcine skin.

DBNP (2,6-di-tert-butyl-4-nitrophenol) has been reported as a potential contaminant in submarines. This yellow substance forms when lubrication oil mist containing the antioxidant additive 2,6-di-tert-butylphenol passes through an electrostatic precipitator and is nitrated. Percutaneous absorption of 14C-DBNP was assessed in the isolated perfused porcine skin flap (IPPSF). Four treatments were studied (n=4 flaps/treatment): 40.0 microgram/cm(2) in 100% ethanol; 40.0 microgram/cm(2) in 85% ethanol/15% H(2)O; 4.0 microgram/cm(2) in 100% ethanol; and 4.0 microgram/cm(2) in 85% ethanol/15% water. DBNP absorption was minimal across all treatment groups, with the highest absorption detected being only 1.08% applied dose in an aqueous ethanol group. The highest mass of 14C-DBNP absorbed was only 0.5 microgram. The majority of the applied dose remained on the surface of the skin. This suggests that there is minimal dermal exposure of DBNP when exposed topically to skin.

Quantum dot penetration into viable human skin.

Systematic studies probing the effects of nanoparticle surface modification and formulation pH are important in nanotoxicology and nanomedicine. In this study, we use laser-scanning fluorescence confocal microscopy to evaluate nanoparticle penetration in viable excised human skin that was intact or tape-stripped. Quantum dot (QD) fluorescent nanoparticles with three surface modifications: Polyethylene glycol (PEG), PEG-amine (PEG-NH2) and PEG-carboxyl (PEG-COOH) were evaluated for human skin penetration from aqueous solutions at pH 7.0 and at pHs of solutions provided by the QD manufacturer: 8.3 (PEG, PEG-NH2) and 9.0 (PEG-COOH). There was some penetration into intact viable epidermis of skin for the PEG-QD at pH 8.3, but not at pH 7.0 nor for any other QD at the pHs used. Upon tape stripping 30 strips of stratum corneum, all QDs penetrated through the viable epidermis and into the upper dermis within 24 h.

Dermatotoxicity of cutting fluid mixtures:in vitro and in vivo studies.

Cutting fluids are widely used in the metal-machining industry to lubricate and reduce heat generation when metals are cut by a metal-cutting tool. These cutting fluids have caused occupational irritant contact dermatitis (OICD), and many of the additives used in these cutting fluid mixtures are thought to be responsible for OICD in workers. The purpose of this study was to assess single or various combinations of these additives in initiating the OICD response following an acute 8-hour exposure in porcine skin in vivo and in vitro using the isolated perfused porcine skin flap (IPPSF) and human epidermal keratinocytes (HEK). Pigs (n = 4) were exposed to 5% mineral oil (MO) or 5% polyethylene glycol (PEG) aqueous mixtures containing various combinations of 2% triazine (TRI), 5% triethanolamine (TEA), 5% linear alkylbenzene sulfonate (LAS), or 5% sulfurized ricinoleic acid (SRA). Erythema and edema were evaluated and skin biopsies for histopathology were obtained at 4 and 8 hours. IPPSFs (n = 4) were exposed to control MO or PEG mixtures and complete MO or PEG mixtures, and perfusate samples were collected hourly to determine interleukin- (IL-) 8 release. The only significant (p < 0.05) mixture effects observed in IPPSFs were with SRA + MO that caused an increase in IL-8 release after 1 or 2 hours' exposure. In vivo exposure to TRI alone appeared to increase erythema, edema, and dermal inflammation compared to the other additives, while SRA alone was least likely to initiate a dermal inflammatory response. In 2-component mixture exposures, the presence of TRI appeared to increase the dermal inflammatory response at 4 and 8 hours especially with the PEG mixtures. In the 3- and 4-component mixtures, MO mixtures are more likely to incite an inflammatory response than PEG mixtures. TRI exhibited the highest toxicity toward HEK, which correlates well to the in vivo irritation and morphology results. In summary, these preliminary studies suggest that the biocide, TRI, is the more potent of the 4 performance additives in causing dermal irritation, and this may vary depending on whether the worker is exposed to a synthetic (PEG)- or MO-based fluid. These findings will however require further clinical studies to validate these acute dermal effects as well as human cumulative irritation following exposure to similar cutting fluid formulations in the workplace.

Skin toxicity of jet fuels: ultrastructural studies and the effects of substance P.

Topical exposure to jet fuel is a significant occupational hazard. Recent studies have focused on dermal absorption of fuel and its components, or alternatively, on the biochemical or immunotoxicological sequelae to exposure. Surprisingly, morphological and ultrastructural analyses have not been systematically conducted. Similarly, few studies have compared responses in skin to that of the primary target organ, the lung. The focus of the present investigation was 2-fold: first, to characterize the ultrastructural changes seen after topical exposure to moderate doses (335 or 67 microl/cm2) of jet fuels [Jet A, Jet Propellant (JP)-8, JP-8+100] for up to 4 days in pigs, and secondly, to determine if co-administration of substance P (SP) with JP-8 jet fuel in human epidermal keratinocyte cell cultures modulates toxicity as it does to pulmonary toxicity in laboratory animal studies. The primary change seen after exposure to all fuels was low-level inflammation accompanied by formation of lipid droplets in various skin layers, mitochondrial and nucleolar changes, cleft formation in the intercellular lipid lamellar bilayers, as well as disorganization in the stratum granulosum-stratum corneum interface. An increased number of Langerhans cells were also noted in jet fuel-treated skin. These changes suggest that the primary effect of jet fuel exposure is damage to the stratum corneum barrier. SP administration decreased the release of interleukin (IL)-8 normally seen in keratinocytes after JP-8 exposure, a response similar to that reported for SP's effect on JP-8 pulmonary toxicity. These studies provide a base upon which biochemical and immunological data collected in other model systems can be compared.