The increasing production and use of fullerene nanomaterials has led to calls for more information regarding the potential impacts that releases of these materials may have on human and environmental health. Fullerene nanomaterials, which are comprised of both fullerenes and surface-functionalized fullerenes, are used in electronic, optic, medical and cosmetic applications. Measuring fullerene nanomaterial concentrations in natural environments is difficult because they exhibit a duality of physical and chemical characteristics as they transition from hydrophobic to polar forms upon exposure to water. In aqueous environments, this is expressed as their tendency to initially (i) self assemble into aggregates of appreciable size and hydrophobicity, and subsequently (ii) interact with the surrounding water molecules and other chemical constituents in natural environments thereby acquiring negative surface charge. Fullerene nanomaterials may therefore deceive the application of any single analytical method that is applied with the assumption that fullerenes have but one defining characteristic (e.g., hydrophobicity). [1] We find that analytical procedures are needed to account for the potentially transitory nature of fullerenes in natural environments through the use of approaches that provide chemically-explicit information including molecular weight and the number and identity of surface functional groups. [2] We suggest that sensitive and mass-selective detection, such as that offered by mass spectrometry when combined with optimized extraction procedures, offers the greatest potential to achieve this goal. [3] With this review, we show that significant improvements in analytical rigor would result from an increased availability of well characterized authentic standards, reference materials, and isotopically-labeled internal standards. Finally, the benefits of quantitative and validated analytical methods for advancing the knowledge on fullerene occurrence, fate, and behavior are indicated.

With production and use of carbon nanoparticles increasing, it is imperative that the toxicity of these materials be determined; yet such testing requires specific and selective analytical methodologies that do not yet exist. Quantitative liquid-liquid extraction was coupled with liquid chromatography/electrospray ionization mass spectrometry for the quantitative determination of fullerenes from C60 to C98. Isotopically enriched, 13C60, was used as an internal standard. The method was applied to determine the loss of C60 from exposure water solution and uptake of C60 by embryonic zebrafish. The average recovery of C60 from zebrafish embryo extracts and 1% DMSO in aqueous-exposure solutions was 90 and 93%, respectively, and precision, as indicated by the relative standard deviation, was 2 and 7%, respectively. The method quantification limit was 0.40 microg/L and the detection limit was 0.02 microg/L. During the toxicological assay, loss of C60 due to sorption to test vials resulted in the reduction of exposure-solution concentrations over 6 h to less than 50% of the initial concentration. Time-course experiments indicated embryo uptake increased over course of the 12-h exposure. A lethal concentration that caused 50% mortality was determined to be 130 microg/L and was associated with a zebrafish embryo concentration, LD50, of 0.079 microg/g of embryo.

Aqueous colloidal suspensions of C60 (aqu/C60) and the C60 derivatives PCBM ([6,6]-phenyl C61-butyric acid methyl ester) and the corresponding butyl and octyl esters, PCBB and PCBO (aqu/PCB-R, where R is an alkyl group), were produced by stirring in double deionized water for 5 months. Kinetically stable fullerene aggregates were formed using this procedure that ranged in intensity-averaged hydrodynamic diameter (Dh) from 193 +/- 2 nm (95% C.L.) for aqu/C60 to 259 +/- 6 nm for aqu/PCBO. Measured zeta potentials (zeta) were < -50 mV, and the isoelectric points (p) were < 1.0 for all of the aqu/fullerenes. Time-resolved dynamic light scattering (TRDLS) was used to measure aqu/fullerene Dh change with time and as a function of background solution ionic strength. The critical coagulation concentration (CCC) values for the aqu/PCB-R fullerenes were significantly higher than that of aqu/C60, indicating that the phenyl alkyl ester moieties of the equ/PCB-R fullerenes were impeding the aggregation process.

When introduced into the aquatic environment, TiO2 NP are likely to settle from the water column, which results in increased exposure of benthic communities. Here, we show that the activity of two extracellular enzymes of intact heterotrophic biofilms, β-glucosidase (carbon-cycling) and l-leucin aminopeptidase (nitrogen-cycling), was reduced following exposure to surface functionalized TiO2 NP and UV radiation, depending on the particles' coating. This reduction was partially linked to ROS production. Alkaline phosphatase (phosphorus-cycling) activity was not affected, however in contrast, an alkaline phosphatase isolated from E. coli was strongly inhibited at lower concentrations of TiO2 NP than the intact biofilms. These results indicate that enzymes present in the biofilm matrix are partly protected against exposure to TiO2 NP and UV radiation. Impairment of extracellular enzymes which mediate the uptake of nutrients from water may affect ecosystem function.