Limited herbivore migration during the Last Glacial Period of Kenya.

Eastern Africa is home to the largest terrestrial migrations on Earth. Though these migratory systems have been well studied for decades, little is known of their antiquity and evolutionary history. Serially sampled strontium stable isotopes (87Sr/86Sr) from tooth enamel can be used to track migration in mammals. Here we analyse 87Sr/86Sr for 79 bovid and equid individuals representing 18 species from four localities in Kenya to characterize prehistoric migratory systems during the Last Glacial Period (115-11.7 ka). Of the species analysed, 16 lack definitive evidence for migration, including blue wildebeest (Connochaetes taurinus), Thomson's gazelle (Eudorcas thomsonii) and plains zebra (Equus quagga), which are long-distance migrants today in the Greater Serengeti Ecosystem and historically in the Athi-Kapiti Plains. Only two species, the extinct wildebeests Rusingoryx atopocranion and Megalotragus sp., were migratory. These findings suggest a possible alternative narrative about ecosystem dynamics during the Last Glacial Period and shed light on the behaviour of both extant and extinct species at this time. In particular, these results indicate that migratory behaviour in extant species either emerged during the Holocene or was more spatiotemporally constrained in the past. Our results contribute to a growing body of evidence suggesting that the structure and function of geologically recent large mammal communities in eastern Africa differed considerably from those observed in the present day.

Industrial Particulate Pollution and Historical Land Use Contribute Metals of Concern to Dust Deposited in Neighborhoods Along the Wasatch Front, UT, USA.

The Salt Lake Valley, UT, USA, is proximal to the desiccating Great Salt Lake (GSL). Prior work has found that this lakebed/playa contributes metals-laden dust to snow in the Wasatch and Uinta Mountains. Dust and industrial particulate pollution are also delivered to communities along the Wasatch Front, but their sources, compositions, and fluxes are poorly characterized. In this study, we analyzed the dust deposited in 18 passive samplers positioned near the GSL, in cities in and near the Salt Lake Valley for total dust flux, the <63 µm dust fraction, 87Sr/86Sr, and trace element geochemistry. We compared spatial patterns in metal flux and abundance with community-level socioeconomic metrics. We observed the highest dust fluxes at sites near the GSL playa. Within the urban corridor, 87Sr/86Sr and trace element relative abundances suggest that most of the dust to which people are regularly exposed may be fugitive dust from local soil materials. The trace metal content of dust deposited along the Wasatch Front exceeded Environmental Protection Agency screening levels and exhibited enrichment relative to both the upper continental crust and the dust collected adjacent to GSL. Sources of metals to dust deposited along the Wasatch Front may include industrial activities like mining, oil refining, as well as past historical pesticide and herbicide applications. Arsenic and vanadium indicated a statistically significant positive correlation with income, whereas lead, thallium, and nickel exhibited higher concentrations in the least wealthy and least white neighborhoods.

Geochemistry and Provenance of Springs in a Baja California Sur Mountain Catchment.

Fractured rock aquifers cover much of Earth's surface and are important mountain sites for groundwater recharge but are poorly understood. To investigate groundwater systematics of a fractured-dominated aquifer in Baja California Sur, Mexico, we examined the spatial patterns of aquifer recharge and connectivity using the geochemistry of springs. We evaluate a range of geochemical data within the context of two endmember hypotheses describing spatial recharge patterns and fracture connectivity. Hypothesis 1 is that the aquifer system is segmented, and springs are fed by local recharge. Hypothesis 2 is that the aquifer system is well connected, with dominant recharge occurring in the higher elevations. The study site is a small <15 km2 catchment. Thirty-four distinct springs and two wells were identified in the study area, and 24 of these sites were sampled for geochemical analyses along an elevation gradient and canyon transect. These analyses included major ion composition, trace element and strontium isotopes, δ18 O and δ2 H isotopes, radiocarbon, and tritium. δ18 O and δ2 H isotopes suggest that the precipitation feeding the groundwater system has at least two distinct sources. Carbon isotopes showed a change along the canyon transect, suggesting that shorter flowpaths feed springs in the top of the transect, and longer flowpaths discharge near the bottom. Geochemical interpretations support a combination of the two proposed hypotheses. Understanding of the connectivity and provenance of these springs is significant as they are the primary source of water for the communities that inhabit this region and may be impacted by changes in recharge and use.

Using strontium isotopes to determine philopatry and dispersal in primates: a case study from Kibale National Park.

Strontium isotope ratios (87Sr/86Sr) allow researchers to track changes in mobility throughout an animal's life and could theoretically be used to reconstruct sex-biases in philopatry and dispersal patterns in primates. Dispersal patterns are a life-history variable that correlate with numerous aspects of behaviour and socio-ecology that are elusive in the fossil record. The present study demonstrates that the standard archaeological method used to differentiate between 'local' and 'non-local' individuals, which involves comparing faunal isotopic ratios with environmental isotopic minima and maxima, is not always reliable; aspects of primate behaviour, local environments, geologic heterogeneity and the availability of detailed geologic maps may compromise its utility in certain situations. This study instead introduces a different methodological approach: calculating offset values to compare 87Sr/86Sr of teeth with that of bone or local environments. We demonstrate this method's effectiveness using data from five species of primates, including chimpanzees, from Kibale National Park, Uganda. Tooth-to-bone offsets reliably indicate sex-biases in dispersal for primates with small home ranges while tooth-to-environment offset comparisons are more reliable for primates with larger home ranges. Overall, tooth-to-environment offsets yield the most reliable predictions of species' sex-biases in dispersal.

Fast exchange of strontium between hair and ambient water: Implication for isotopic analysis in provenance and forensic studies.

Trace elements in hair originate from intake (e.g., diet, inhalation, skin absorption), are transported in the bloodstream, and then incorporated during hair formation. However, the trace element abundance and isotopic compositions may be altered by post-eruption environmental processes. Such alterations must be addressed to obtain a meaningful interpretation of hair analysis for biomonitoring. In this study, we used strontium (Sr) isotopic analysis together with sorption kinetics of ionic Sr to quantify the rate and extent of replacement of endogenous Sr in hair by exogenous Sr from ambient water. We found that with only 10 minutes of exposure at room temperature (22°C), more than 30% of original endogenous Sr in hair was replaced with exogenous Sr from the solution. After 16 days of exposure to the solution, more than 90% of endogenous Sr was replaced, with a warmer temperature (60°C) accelerating the exchange substantially. We also found that acid leaching of exposed hair did not remove or isolate the exogenous Sr; therefore, neither the original endogenous nor the exogenous 87Sr/86Sr signal could be separated. Nonetheless, these findings illustrated that the quantitative correlation between the fraction of exogenous Sr and the soaking time, if established, could be used to estimate the length of water contact time for hair in forensic studies. Even if such time since initial contact cannot be established, the combination of acid leaching and 87Sr/86Sr analysis of hair samples may still be valuable in provenance studies to identify recent changes in the exogenous Sr pool, including movements or changes in water source.

Distinguishing the region-of-origin of roasted coffee beans with trace element ratios.

Determining coffee region-of-origin is most appropriately addressed through analyses of the product available to the consumer. We analyzed the concentrations of 44 trace elements in 53 samples of roasted Arabica coffee beans (Coffea arabica) from 21 different countries. Variations in absolute elemental concentrations of coffee beans arise through varying degrees of roasting (from green through dark roasts). Since trace elements are not volatilized at roasting temperatures, we conducted analyses of element ratios to evaluate concentration-related differences among beans of different origins. We used kernel density estimates to compare the distributions of 1892 element ratios for each of these countries with the combined distribution of coffee samples from the other countries. Using this quantitative approach, we demonstrated that many of the world's coffee-producing regions can be distinguished from other regions of the world on the basis of element ratios.

Analysis of retention of gadolinium by brain, bone, and blood following linear gadolinium-based contrast agent administration in rats with experimental sepsis.

PURPOSE: It is important to identify populations that may be vulnerable to the brain deposition of gadolinium (Gd) from MRI contrast agents. At intervals from 24 hours to 6 weeks following injection of a linear Gd contrast agent, the brain, blood and bone content of Gd were compared between control rats and those with experimental endotoxin-induced sepsis that results in neuroinflammation and blood-brain barrier disruption. METHODS: Male rats were injected intraperitoneally with 10 mg/kg lipopolysaccharide. Control animals received no injection. Twenty-four hours later, 0.2 mmol/kg of gadobenate dimeglumine was injected intravenously. Brain, blood, and bone Gd levels were measured at 24 hours, 1 week, 3 weeks, and 6 weeks by inductively coupled plasma mass spectroscopy. RESULTS: Blood Gd decreased rapidly between 24 hours and 1 week, and thereafter was undetectable, with no significant difference between lipopolysaccharide and control rats. Brain levels of Gd were significantly higher (4.29-2.36-fold) and bone levels slightly higher (1.35-1.11-fold) in lipopolysaccharide than control rats at all time points with significant retention at 6 weeks. CONCLUSION: Experimental sepsis results in significantly higher deposition of Gd in the brain and bone in rats. While blood Gd clears rapidly, brain and bone retained substantial Gd even at 6 weeks following contrast injection.

Detecting riparian habitat preferences in "savanna" chimpanzees and associated Fauna with strontium isotope ratios: Implications for reconstructing habitat use by the chimpanzee-human last common ancestor.

OBJECTIVES: Riparian or gallery forests are critical habitats for numerous plants and animals today. Paleoanthropologically, reliance on such habitats informs behavioral and ecological reconstructions; for example, gallery forest habitats likely played a critical role in the transition from ape to hominin in the early Pliocene and may represent a preferred habitat for the last common ancestor of chimpanzees and humans. Direct indicators for gallery forest habitats preference are lacking. The objective of this article is to assess whether strontium isotope ratios are a reliable indicator of habitat preference for fauna living in and around gallery forests. MATERIALS AND METHODS: We report bioavailable strontium isotope ratios from the Mugiri River, its tributaries, and its gallery forest (Toro-Semliki Wildlife Reserve, southwestern Uganda), and compare them to surrounding savanna-grassland values. We compare these environmental values to strontium isotopes ratios in faunal tooth enamel to determine if habitat preferences are accurately reflected. RESULTS: Gallery forest and savanna-grassland vegetations have significantly different strontium isotope ratio profiles. We trace these isotopic differences to the influence of the Mugiri tributaries, which originate on Paleoproterozoic gneiss deposits on top of the surrounding escarpments. These isotopic differences in vegetation are mirrored in the tissues of fauna with habitat preferences for either the gallery forest or the surrounding grasslands. DISCUSSION: This research demonstrates the potential of strontium isotope ratios to identify habitat preferences in modern or fossil fauna under proper geologic variability. It provides a methodological model for future studies seeking to reconstruct habitat preferences in early hominins.

Trace element concentrations in horn: Endogenous levels in keratin and susceptibility to exogenous contamination.

As a recorder containing both physiological and environmental information, keratinized tissues, such as hair and feather, can be used to reveal geographical information, to monitor the exposure to pollutants, and to reconstruct dietary history. However, trace element analysis of keratinized tissues is complicated by the lack of reference endogenous ranges of trace element and the lack of understanding of the susceptibility of each element to exogenous contamination. The interior of animal horn is the cleanest of all keratinized tissues with minimum exogenous contamination because of its large size. Thus, the trace element concentrations in horn interior samples can provide reliable endogenous concentration ranges. Here we measured the concentrations of trace elements in horn interior samples of cattle and wild animals, which we propose to be used as the reference ranges for endogenous levels of trace elements in keratin. We calculated the enrichment factors of 30 trace elements in horn interior samples relative to the continental crust, which we considered the average exogenous contamination. We compared the ranges of elemental concentrations measured in horn interior samples, in the order of decreasing enrichment factor, to their reference ranges in hair, fingernails, and toenails, as well as their concentrations in caprine horns. Such comparison validates the use of the enrichment factor as an indicator of the susceptibility of an element to contamination: an element with a high enrichment factor is generally less likely to be affected by contamination and vice versa.

Shifting habitat mosaics and fish production across river basins.

Watersheds are complex mosaics of habitats whose conditions vary across space and time as landscape features filter overriding climate forcing, yet the extent to which the reliability of ecosystem services depends on these dynamics remains unknown. We quantified how shifting habitat mosaics are expressed across a range of spatial scales within a large, free-flowing river, and how they stabilize the production of Pacific salmon that support valuable fisheries. The strontium isotope records of ear stones (otoliths) show that the relative productivity of locations across the river network, as both natal- and juvenile-rearing habitat, varies widely among years and that this variability is expressed across a broad range of spatial scales, ultimately stabilizing the interannual production of fish at the scale of the entire basin.

Isotopes in teeth and a cryptic population of coastal freshwater seals.

Human activities threaten the biodiversity of aquatic mammals across the globe. Conservation of these species hinges on the ability to delineate movements and foraging behaviors of animals, but gaining such insights is hampered by difficulties in tracing individuals over their lives. We determined isotope ratios in teeth (87 Sr/86 Sr, 13 C/12 C, and 18 O/16 O) to examine lifelong movement and resource-use patterns of a unique freshwater population of a wide-ranging pinniped species (harbor seal [Phoca vitulina]) that resides in Iliamna Lake, Alaska (U.S.A.). This population's potentially unique migratory behavior and use of different trophic resources are unknown. The isotope ratios we measured in teeth showed that seals were born in the lake, remained lifelong residents, and relied principally on resources produced from in the lake, even when seasonally abundant and nutrient-dense spawning anadromous fish (i.e., sockeye salmon [Oncorhynchus nerka]) were available in the lake. Our results illustrate how serial isotope records in teeth, particularly 87 Sr/86 Sr ratios, can be used to quantify how coastal mammal populations exploit both freshwater and marine ecosystems. Understanding lifelong patterns of habitat and resource use is essential information when designing effective conservation plans for threatened coastal mammals. We present the Iliamna Lake harbor seals as a unique case study into how isotope records within teeth can help reveal the cryptic ecology of such a population residing in an intact ecosystem. The results also provide critical baseline information for the Kvichak River system, which is facing an uncertain future due to proposed large-scale industrial development and a rapidly changing climate.

Isotopos Dentales y una Población Críptica de Focas Costeras de Agua Dulce Resumen Las actividades humanas amenazan a la diversidad de mamíferos acuáticos en todo el mundo. La conservación de estas especies depende de la habilidad para delinear los movimientos y los comportamientos de búsqueda de alimento de los animales, pero la obtención de dicha información está obstaculizada por las dificultades en el rastreo de individuos a lo largo del transcurso de sus vidas. Determinamos la proporción de isotopos dentales (87 Sr/86 Sr, 13 C/12 C y 18 O/16 O) para examinar el movimiento a lo largo de la vida y los patrones de uso de recursos de una población única de una especie de pinnípedos de agua dulce con una distribución amplia (foca común [Phoca vitulina]), la cual reside en el lago Iliamna, Alaska (E.U.A.). Se desconocen el comportamiento migratorio potencialmente único de esta población y el uso que le dan a los diferentes recursos tróficos. La proporción de isotopos que medimos en los dientes mostró que las focas nacieron en el lago, permanecieron como residentes de toda la vida y dependieron principalmente de los recursos producidos en el lago, incluso cuando estaban disponibles en aquel lugar por razones reproductivas los peces anádromos abundantes estacionalmente y con densidad de nutrientes (es decir, el salmón rojo [Oncorhynchus nerka]). Nuestros resultados ilustran cómo los registros seriales de isotopos dentales, particularmente la proporción 87 Sr/86 Sr, pueden usarse para cuantificar cómo las poblaciones de mamíferos costeros explotan tanto los ecosistemas marinos como los de agua dulce. El entendimiento de los patrones ontogénicos del uso de recursos y de hábitat es esencial cuando se diseñan planes efectivos de conservación para los mamíferos costeros en peligro. Presentamos a las focas comunes del lago Iliamna como un estudio de caso único sobre cómo los registros de isotopos dentales pueden ayudar a revelar la ecología críptica de dicha población que reside en un ecosistema intacto. Los resultados también proporcionan información importante de línea base para el sistema el río Kvichak, el cual está enfrentando un futuro incierto debido a la propuesta de un desarrollo industrial de gran escala y al rápido clima cambiante.

Longitudinal and transverse variation of trace element concentrations in elephant and giraffe hair: implication for endogenous and exogenous contributions.

The spatial distribution of trace elements in hair is highly heterogeneous at the microscale. The relatively mild spatial variation of endogenous signal incorporated during hair growth may be amplified by orders of magnitude due to later exogenous contaminations. Here, we studied the longitudinal and transverse distributions of trace elements in elephant and giraffe hair and discussed the possible endogenous and exogenous contributions. Laser ablation ICP-MS analyses were performed on cross sections of hair to assess the surface contamination and transverse variation. We also removed the contaminated surface layer at various distances from hair root of single hair strands using physical abrasion and measured the concentrations by microwave digestion followed by ICP-MS. By comparing the concentrations of 11 trace elements between the intact and abraded hair segments as a function of distance from root and their laser ablation profiles, we rationalized the endogenous and exogenous contributions: Al and Ti concentrations are dominated by the exogenous contamination on the elephant hair surface, probably in the form of insoluble particles, but not in the giraffe hair; Mg, Ca, Sr, Ba, and Mn are enhanced on the elephant hair surface by exogenous contaminations, but a comparable amount was found in the hair interior suggesting migration of these elements from the surface towards the core; Cu, Zn, Se, and Pb did not have surface accumulation and thus were dominated by the endogenous signal. Overall, giraffe hair had minimal surficial contamination, suggesting the origin of its trace elements is predominantly endogenous, except for Mn, which might get contaminated with airborne particles. We thus demonstrate that contamination of hair may be strongly related to behavioral traits and that the interpretation of trace elemental analyses in hair as a biomonitor or for provenance studies would be highly dependent on the species considered.

Stable isotope ecology of black rhinos (Diceros bicornis) in Kenya.

Stable isotope and elemental ratios in hair are influenced by the environment, including both climate and geology. Stable carbon isotopes can be used to give estimates of the C4/CAM fraction of diets of herbivorous mammals; stable nitrogen isotopes are related to the local water deficit; strontium isotopes are determined by the local geology. We studied hair from rhinos in Kenya to determine spatial patterns in δ13C, δ15N, and 87Sr/86Sr ratios. The samples of rhino hair were collected during Kenya Wildlife Service translocation or veterinary activities. δ13C values showed diets dominated by C3 foods, but in some regions the diet, at least seasonally, contained significant quantities (i.e., > ca. 20%) of C4/CAM foods. δ15N values were related to water deficit, with higher δ15N values in regions with high water deficit. 87Sr/86Sr isotope ratios were found to be related to the local geological substrate suggesting that 87Sr/86Sr isotope ratios are provisionally useful for determining the origins of illegal wildlife materials in Kenya and elsewhere in Africa.

Reconstruction of travel history using coupled δ18 O and 87 Sr/86 Sr measurements of hair.

RATIONALE: Oxygen isotope ratios (δ18 O values) of hair largely reflect features of regional hydrology while strontium isotope ratios (87 Sr/86 Sr) are thought to reflect bedrock geology; combination of both isotope signatures may provide greater capacity for determining provenance and reconstructing travel history of an organism. To test this hypothesis, we compared the O-Sr isotope profiles of hair from domestic horses with known residency histories. METHODS: Tail hairs were collected from a pair of horses pastured together for a period of 16 months, one of which lived in a different location for the 8 months prior. Hair samples were washed with solvents to remove external contaminants prior to sequential sampling for δ18 O and 87 Sr/86 Sr analysis via TC/EA-IRMS and MC-ICP-MS, respectively. Hair digests were concentrated and analyzed employing low-flow natural aspiration to measure 87 Sr/86 Sr. RESULTS: Tail hair from the control and transported horses had mean δ18 O values of 11.25 ± 1.62 ‰ and 10.96 ± 1.53 ‰, and mean 87 Sr/86 Sr of 0.7101 ± 0.0006 and 0.7109 ± 0.0020, respectively. The δ18 O and 87 Sr/86 Sr profiles for the control and transported horses were indistinguishable when they were pastured together. The 87 Sr/86 Sr profiles were significantly different during the period that the horses were living apart, while the δ18 O values were indistinguishable during that period. CONCLUSIONS: By comparing the O-Sr isotope profiles of a control and transported horse, we investigated isotopic signal(s) potentially useful for reconstructing travel histories via high-resolution sequential sampling along single strands of tail hair. Improved analytical capabilities allowed for extremely low Sr abundance samples to be analyzed for 87 Sr/86 Sr and proved capable of resolving a horse's movement between distinct regions. Copyright © 2017 John Wiley & Sons, Ltd.

Strontium isotopes delineate fine-scale natal origins and migration histories of Pacific salmon.

Highly migratory organisms present major challenges to conservation efforts. This is especially true for exploited anadromous fish species, which exhibit long-range dispersals from natal sites, complex population structures, and extensive mixing of distinct populations during exploitation. By tracing the migratory histories of individual Chinook salmon caught in fisheries using strontium isotopes, we determined the relative production of natal habitats at fine spatial scales and different life histories. Although strontium isotopes have been widely used in provenance research, we present a new robust framework to simultaneously assess natal sources and migrations of individuals within fishery harvests through time. Our results pave the way for investigating how fine-scale habitat production and life histories of salmon respond to perturbations-providing crucial insights for conservation.

Potential impacts to perennial springs from tar sand mining, processing, and disposal on the Tavaputs Plateau, Utah, USA.

Similar to fracking, the development of tar sand mining in the U.S. has moved faster than understanding of potential water quality impacts. Potential water quality impacts of tar sand mining, processing, and disposal to springs in canyons incised approximately 200 m into the Tavaputs Plateau, at the Uinta Basin southern rim, Utah, USA, were evaluated by hydrogeochemical sampling to determine potential sources of recharge, and chemical thermodynamic estimations to determine potential changes in transfer of bitumen compounds to water. Because the ridgetops in an area of the Tavaputs Plateau named PR Spring are starting to be developed for their tar sand resource, there is concern for potential hydrologic connection between these ridgetops and perennial springs in adjacent canyons on which depend ranching families, livestock, wildlife and recreationalists. Samples were collected from perennial springs to examine possible progression with elevation of parameters such as temperature, specific conductance, pH, dissolved oxygen, isotopic tracers of phase change, water-rock interaction, and age since recharge. The groundwater age dates indicate that the springs are recharged locally. The progression of hydrogeochemical parameters with elevation, in combination with the relatively short groundwater residence times, indicate that the recharge zone for these springs includes the surrounding ridges, and thereby suggests a hydrologic connection between the mining, processing, disposal area and the springs. Estimations based on chemical thermodynamic approaches indicate that bitumen compounds will have greatly enhanced solubility in water that comes into contact with the residual bitumen-solvent mixture in disposed tailings relative to water that currently comes into contact with natural tar.

Total- and methyl-mercury concentrations and methylation rates across the freshwater to hypersaline continuum of the Great Salt Lake, Utah, USA.

We examined mercury (Hg) speciation in water and sediment of the Great Salt Lake and surrounding wetlands, a locale spanning fresh to hypersaline and oxic to anoxic conditions, in order to test the hypothesis that spatial and temporal variations in Hg concentration and methylation rates correspond to observed spatial and temporal trends in Hg burdens previously reported in biota. Water column, sediment, and pore water concentrations of methylmercury (MeHg) and total mercury (THg), as well as related aquatic chemical parameters were examined. Inorganic Hg(II)-methylation rates were determined in selected water column and sediment subsamples spiked with inorganic divalent mercury (204Hg(II)). Net production of Me204Hg was expressed as apparent first-order rate constants for methylation (kmeth), which were also expanded to MeHg production potential (MPP) rates via combination with tin reducible 'reactive' Hg(II) (Hg(II)R) as a proxy for bioavailable Hg(II). Notable findings include: 1) elevated Hg concentrations previously reported in birds and brine flies were spatially proximal to the measured highest MeHg concentrations, the latter occurring in the anoxic deep brine layer (DBL) of the Great Salt Lake; 2) timing of reduced Hg(II)-methylation rates in the DBL (according to both kmeth and MPP) coincides with reduced Hg burdens among aquatic invertebrates (brine shrimp and brine flies) that act as potential vectors of Hg propagation to the terrestrial ecosystem; 3) values of kmeth were found to fall within the range reported by other studies; and 4) MPP rates were on the lower end of the range reported in methodologically comparable studies, suggesting the possibility that elevated MeHg in the anoxic deep brine layer results from its accumulation and persistence in this quasi-isolated environment, due to the absence of light (restricting abiotic photo demethylation) and/or minimal microbiological demethylation.

Circuit modification in electrical field flow fractionation systems generating higher resolution separation of nanoparticles.

Compared to other sub-techniques of field flow fractionation (FFF), cyclical electrical field flow fractionation (CyElFFF) is a relatively new method with many opportunities remaining for improvement. One of the most important limitations of this method is the separation of particles smaller than 100nm. For such small particles, the diffusion rate becomes very high, resulting in severe reductions in the CyElFFF separation efficiency. To address this limitation, we modified the electrical circuitry of the ElFFF system. In all earlier ElFFF reports, electrical power sources have been directly connected to the ElFFF channel electrodes, and no alteration has been made in the electrical circuitry of the system. In this work, by using discrete electrical components, such as resistors and diodes, we improved the effective electric field in the system to allow high resolution separations. By modifying the electrical circuitry of the ElFFF system, high resolution separations of 15 and 40nm gold nanoparticles were achieved. The effects of applying different frequencies, amplitudes and voltage shapes have been investigated and analyzed through experiments.

A review of exosome separation techniques and characterization of B16-F10 mouse melanoma exosomes with AF4-UV-MALS-DLS-TEM.

Exosomes participate in cancer metastasis, but studying them presents unique challenges as a result of their small size and purification difficulties. Asymmetrical field flow fractionation with in-line ultraviolet absorbance, dynamic light scattering, and multi-angle light scattering was applied to the size separation and characterization of non-labeled B16-F10 exosomes from an aggressive mouse melanoma cell culture line. Fractions were collected and further analyzed using batch mode dynamic light scattering, transmission electron microscopy and compared with known size standards. Fractogram peak positions and computed radii show good agreement between samples and across fractions. Ultraviolet absorbance fractograms in combination with transmission electron micrographs were able to resolve subtle heterogeneity of vesicle retention times between separate batches of B16-F10 exosomes collected several weeks apart. Further, asymmetrical field flow fractionation also effectively separated B16-F10 exosomes into vesicle subpopulations by size. Overall, the flow field flow fractionation instrument combined with multiple detectors was able to rapidly characterize and separate exosomes to a degree not previously demonstrated. These approaches have the potential to facilitate a greater understanding of exosome function by subtype, as well as ultimately allow for "label-free" isolation of large scale clinical exosomes for the purpose of developing future exosome-based diagnostics and therapeutics.

Biased cyclical electrical field flow fractionation for separation of sub 50 nm particles.

Cyclical electrical field flow fractionation (CyElFFF) is a technique for characterizing and separating nanoparticles based on their size and charge using cyclical electric fields. The high diffusion rate of nanoparticles has prevented CyElFFF from being applicable to particles smaller than 100 nm. In this work, the diffusion challenges associated with nanoparticles was resolved using biased cyclical electric fields. This new method, biased cyclical electrical field flow fractionation (BCyElFFF), achieves baseline separation of 15 and 40 nm gold nanoparticles. Theoretical considerations show that the optimal resolution is achieved when the applied bias yields electrical transport that counteracts the diffusive transport of nanoparticles. BCyElFFF greatly extends separation capabilities of the cyclical electrical field flow fractionation to sub 50 nm nanoparticles and provides a powerful alternative to other separation and characterization techniques capable of separating nanoparticles smaller than 50 nm.