Laser Ablation Inductively Coupled Plasma Mass Spectrometry Analysis Research Articles

Topical delivery of PD‐1 inhibitors with laser‐assisted passive diffusion and active intradermal injection: Investigation of cutaneous pharmacokinetics and biodistribution patterns

Current cancer immunotherapeutic treatment with PD-1 inhibitors is administered systemically. However, a local treatment strategy may be advantageous as it could provide targeted drug delivery as well as attenuate side effects seen with systemic treatments. For keratinocyte cancers, where surgical excision is not always applicable, an alternate local treatment approach would be beneficial. This study aims to examine cutaneous pharmacokinetics and biodistribution of the PD-1 inhibitor nivolumab, locally delivered either by ablative fractional laser (AFL)-assisted passive diffusion or active intradermal injection, in vivo. In vivo pig skin was either exposed to CO2 AFL (80 mJ/mb by two stacked pulses of 40 mJ/mb) at 5% or 15% density followed by topical application of nivolumab (1 mg/ml, 100 µl/10 × 10 mm) or intradermally injected with nivolumab (1 mg/ml, 100 µl). Cutaneous nivolumab delivery was evaluated at different timepoints (0, 1, 2, 4 hours and 2 days) at two tissue depths (100-800 and 900-1600 µm) by ELISA. Visualization of cutaneous biodistribution was shown in vertical tissue sections using HiLyte FluorTM 488 SE labeled nivolumab for fluorescence microscopy whereas nivolumab was DOTA-tagged with Dysprosium before the laser ablation-inductively coupled plasma-mass spectrometry analysis (LA-ICP-MS). Our in vivo study revealed different pharmacokinetic and biodistribution patterns for the AFL- and injection techniques. A superficial horizontal band-like uptake of nivolumab was provided with AFL-assisted passive diffusion whereas a deep focal deposition was seen with active intradermal injection, compared with controls showing remnant deposition on the skin surface. AFL-assisted nivolumab uptake in upper dermis peaked after 4 hours (p < 0.01). The cutaneous concentration of nivolumab achieved by intradermal injection was markedly higher than with AFL, the highest deposition with intradermal injection was detected at time 0 hours in both upper and deep dermis (p < 0.01) and decreased throughout the study period, although the concentration remained higher compared with saline control injections at all time points (0 hours -2 d) (p < 0.01). Local cutaneous delivery of nivolumab with either AFL or intradermal injection revealed two different pharmacokinetic and biodistribution patterns. Passive AFL-assisted diffusion of nivolumab resulted in enhanced uptake after 4 hours, while intradermal actively injected nivolumab showed immediate enhanced cutaneous deposition with retention up to 2 days after injection. The two local delivery techniques show potential for development of individualized treatment strategies depending on the clinical tumor appearance.

U-Pb systematics of uranium-rich apatite from Adirondacks: Inferences about regional geological and geochemical evolution, and evaluation of apatite reference materials for in situ dating

High‑uranium apatite samples from iron oxide-apatite (IOA) deposits of the eastern Adirondack Mountains, New York, are evaluated as potential standards for in situ U-Pb dating of high-U apatite. Age data for these minerals also have implications for better understanding the geological evolution in the region. Secondary ion mass spectrometry (SIMS), and laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) analyses of these samples show that they have high and variable uranium contents of 5–485 ppm. High-precision isotope-dilution thermal ionization mass spectrometry (ID-TIMS) dating yielded U–Pb errorchron ages of 907 ± 14 Ma (MSWD = 20) and 924 ± 13 Ma (MSWD = 547), showed disturbance in the U–Pb systems, and revealed radiogenic compositions of initial Pb (206Pb/204Pb ratios of 339 ± 48 and 162 ± 39). Nominal age calculations using assumed initial Pb isotopic compositions close to average terrestrial crustal Pb yield biased and older ages despite the radiogenic Pb isotopic composition of the apatites (206Pb/204Pb from 1300 to >4000). The apatite ages calculated using the measured initial Pb isotopic compositions are younger than the U–Pb ages of 1008.0 ± 3.2 Ma and 992.4 ± 7.7 Ma determined by SIMS for zircon cores and rims, respectively, separated from one of these ore samples. It indicates protracted fluid activity in the deposit that lasted for ~100 Ma after the ore formation, or later disturbance of the apatite. The time of U enrichment that we inferred from radiogenic composition of initial Pb is within uncertainties with primary ore crystallization, indicating that high 206Pb/204Pb ratios of initial Pb were caused by dissolution-reprecipitation of primary apatite.Despite the variability in U contents and disturbance of the U–Pb system in the apatites, our SIMS and LA-ICPMS analyses show that these samples can be used, with due caution, as reference materials (RMs) for dating apatite with similarly high-U concentration. They potentially provide more precise and accurate results compared to the usage of better behaved but lower-U apatite RMs due to improved counting statistics and reduced matrix effects, especially important for LA-ICPMS with less sensitive quadrupole mass analysers.The McClure Mountain apatite, a widely used reference for in situ dating, was used in the present study as a matrix-matched reference material for in situ LA-ICPMS analyses. We also analysed it by ID-TIMS and obtained more radiogenic Pb-isotopic data and more precise ages that are in agreement within uncertainties with the previously published result (Schoene and Bowring, 2006); combined data yielded a U-Pb errorchron age of 525.3 ± 1.7 Ma (MSWD = 70). The data corrected for initial Pb using the total U/Pb isochron yield the single Concordia age of 525.10 ± 0.75 Ma (MSWD = 1.1). Two independent ID-TIMS U–Pb studies support the use of this apatite as a primary RM for dating of low-U apatite with a normal composition of initial Pb. However, its small grain size and low U concentration (11–29 ppm) can cause elevated uncertainty in LA-ICPMS age determinations for unknowns. Better precision in our LA-ICPMS analyses was achieved using Madagascar (MAD1 and MAD2) apatite RM with U contents in the range of 28–58 ppm.

Additive manufacturing of platinum group element (PGE) reference materials with a silica matrix.

The microanalytical community has an outstanding need for platinum group element (PGE) reference materials, particularly for trace element analysis by laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS). National Institute of Standards and Technology (NIST) glasses contain Rh, Pd, and Pt, but lack Ru, Os, and Ir. Synthesis of silicate PGE standards has proven difficult due the tendency of PGEs to form metallic nuggets. Additive manufacturing methods were used to produce PGE standards with a silica matrix. Monodispersed submicron PGE-doped Stöber particles were used as feedstock materials for electrophoretic deposition (EPD). Two-cm-sized samples produced by EPD were subsequently densified by thermal processing. The homogeneity of PGEs was tested using LA-ICPMS and concentrations were measured by laser ablation and solution ICPMS. The PGE concentrations ranged from 0.5 to 3 μg/g. The inhomogeneity was at the 3% RSD level for Ru, Rh, Ir, and Os throughout and 5% for Pt and Pd in the interior of the samples. Based on LA-ICPMS analyses, the interiors of the two samples have near identical concentrations in PGEs. The samples fabricated in this study represent the most complete and homogeneous PGE standards produced with a silicate matrix. The ability to produce multiple samples with the same composition provides opportunities for validating methods, monitoring long-term reproducibility, and facilitating interlaboratory comparisons.

Rapid determination of initial 87Sr/86Sr and estimation of the Rb-Sr age of plutonic rocks by LA-ICPMS of variably altered feldspars: An example from the 1.14 Ga Great Abitibi Dyke, Ontario, Canada

Sr isotope analysis of plutonic rocks is an important method for deriving the provenance and age of ancient magmatic episodes, and the petrogenetic processes operating during intrusive activity. We determined the 87Sr/86Sr isotopic compositions of fresh and variably altered feldspars from the 1.14 Ga gabbroic Great Abitibi Dyke, Ontario, Canada, through the use of Laser Ablation Inductively-Coupled Plasma Mass Spectrometry (LA-ICPMS). The data show an alteration trend between fresh, low-Rb plagioclase with 87Sr/86Sr ratios of 0.7045 and high-Rb alkali feldspar with 87Sr/86Sr ratios of 0.7059, which may be used to constrain the 87Sr/86Sr ratio of the mantle source. This trend is incompatible with simple mixing and instead has age significance. As post-intrusive alteration through hydrothermal circulation starts immediately following emplacement, LA-ICPMS analysis allows rapid estimation of initial 87Sr/86Sr ratios and intrusive age, suitable for sample screening and selection for more precise dating. For the Great Abitibi Dyke, the Rb-Sr age estimate of emplacement of 1.10 ± 0.23 Ga (2σ) is concordant with the precise U-Pb emplacement age of the dyke (1140.6 ± 2.0 Ma). The most altered high-Rb alkali feldspars return younger ages, suggesting that post-intrusive alteration lasted several hundred million years. This study highlights the need for microanalysis to differentiate between alteration and magmatic processes on basis of Sr isotopic signatures, and outlines a rapid method to determine initial 87Sr/86Sr ratios and to estimate Rb-Sr ages of plutonic rocks in terranes with long histories of multiple intrusive magmatic episodes.

Effect of dibutyltin on placental and fetal toxicity in rat

In order to elucidate the effect of chorioallantoic and yolk sac placenta on the embryonic/fetal toxicity in dibutyltin dichloride (DBTCl)-exposed rats, we examined the histopathological changes and the tissue distribution of dibutyltin in the placentas and embryos. DBTCl was orally administered to the groups at doses of 0 mg/kg during gestation days (GD)s 7-9 (control group) and 20 mg/kg during GDs 7-9 (GD7-9 treated group), and GDs 10-12 (GD10-12 treated group). The total fetal mortality was increased, and malformations characterized by craniofacial dysmorphism were detected in the GD7-9 treated group. The embryonic/fetal weight and placental weight showed a decrease in both DBTCl-treated groups. Histologically, some embryos on GD 9.5 in the GD7-9 treated group underwent apoptosis without any changes of yolk sac. In the laser ablation-inductively coupled plasma-mass spectrometry analysis (LA-ICP-MS), tin was detected in the embryo, allantois, yolk sac, ectoplacental cone and decidual mass surrounding the conceptus on GD 9.5 in the GD7-9 treated group. Thus, it is considered that the embryo in this period is specifically sensitive to DBTCl-induced apoptosis, compared with other parts. The chorioallantoic placentas in both DBTCl-treated groups showed the developmental delay and hypoplasia in the fetal parts of placenta, resulting from apoptosis and mitotic inhibition. Thus, it was speculated that the DBTCl-induced malformations and fetal resorption resulted from the apoptosis in the embryo caused by the direct effect of DBTCl. The DBTCl-induced lesions in the chorioallantoic placenta were a non-specific transient developmental retardation in the fetal parts of placenta, leading to intrauterine growth retardation.

Determination of Cl and Br concentrations in individual fluid inclusions by combining microthermometry and LA-ICPMS analysis: Implications for the origin of salinity in crustal fluids

The origin of salinity in crustal fluids can be deduced from their Cl, Br and Na concentrations and associated Cl/Br and Na/Br ratios. Here, a protocol for quantitative analysis of Cl, Br and Na concentration in individual fluid inclusions of variable size, bulk salinity, Cl, Br and Na contents is presented. It combines microthermometry and laser ablation — inductively coupled plasma mass spectrometry (LA-ICPMS) analysis.The method is based on: (i) microthermometric measurement of ice melting, hydrate melting, halite dissolution and sylvite dissolution temperatures in fluid inclusions; (ii) calibration of LA-ICPMS signals of Br by analyzing Na–Br–Cl standard solutions loaded in silica glass capillaries; (iii) calculation of solute (Cl, Na, Ca, K, Mg) concentration based on LA-ICPMS intensities and the Pitzer thermodynamic model (for inclusions of salinity below 23wt.% equivalent NaCl), or a charge-balance approach (for higher salinity inclusions) and (iv) calculation of uncertainty on Cl, Br and Na concentration and Cl/Br and Na/Br ratios in the fluid.This method is applied to natural fluid inclusions with variable Cl, Br and Na contents as previously determined by microthermometry and bulk crush-leach coupled with ion chromatography analysis. The studied materials consist of: i) low-salinity inclusions from Alpine quartz veins and ii) high-salinity inclusions from the Trimouns talc deposit and from Athabasca Basin uranium deposits. Molar Cl/Br and Na/Br ratios range from 140±50 to 1200±400 and 17±6 to 880±290 in the analyzed inclusions. The calculated uncertainty on Cl/Br and Na/Br ratios in individual fluid inclusions is between 30 and 38%, regardless of the salinity. It appears that the analysis of individual inclusions coupled with uncertainty calculation allows the identification of significant variation of Cl/Br and Na/Br ratios within individual samples that could not be identified from previous bulk crush-leach and ion chromatography analyses. Because Br is a minor solute (molar Cl/Br is between ~100 and ~10000 in most crustal fluids), and because of its high first ionization energy, the determination of Br concentration in individual inclusion by combining microthermometry and LA-ICPMS analysis is most readily achievable for large (>50μm in diameter) inclusions. For smaller inclusions (10 to 50μm in diameter), the applicability of the present method is more sensitive to the Br concentration.

Modification of gas speciation in quartz-hosted fluid inclusions by stray laser radiation during LA-ICPMS analysis

Laser-ablation inductively coupled-plasma mass spectrometry (LA-ICPMS) is an established method of analyzing the elemental composition of individual fluid inclusions in minerals. While the method affords good spatial control of ablation pits, we have found that stray light from the UV (193 nm) laser may permanently modify the gas species in adjacent fluid inclusions. We have used Raman spectroscopy to analyze natural fluid inclusions in quartz before and after ablating test pits. New molecular species (CO, H 2 , and O 2 ) appeared in the vapor phases of inclusions near the pits, resulting in complex, disequilibrium gas mixtures (e.g., CO 2 -CH 4 -H 2 O-CO-H 2 -O 2 ) and formation of iron oxyhydroxides in brine inclusions. Ablation for 40 s with a laser fluence of ~24 J/cm 2 on the sample produced the new gas species in inclusions at various distances up to 210 μm from the pits, depending on pit diameter. We attribute the changes in gas speciation to molecular photodissociation induced by stray UV-laser light. We have no evidence that this artifact changes the bulk elemental composition or density of the affected inclusions. The problem for fluid inclusion analysis is that phase-transition temperatures (e.g., clathrate hydrate dissociation, partial homogenization of the carbonic phases, and total homogenization) are highly sensitive to the mixture of gas species present. This means that parameters such as gas compositions, bulk salinity, and minimum entrapment temperatures are likely to be misinterpreted if inclusions are analyzed by microthermometry or Raman spectroscopy in samples that have already undergone laser ablation.

Laser Ablation-Inductively Coupled Plasma Mass Spectrometry for the Characterization of Pigments in Prehistoric Rock Art

In this work, several red-colored paintings of post-Paleolithic schematic style found in 10 different shelters in the vicinity of the Vero River (Huesca) were sampled and subjected to analysis by means of scanning electron microscopy-energy-dispersive X-ray spectrometry (SEM-EDX), Raman spectroscopy, and laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS). The goal of this research was to obtain meaningful information on the samples composition, in order to establish differences or similarities among them. The combined use of these techniques proved beneficial, as Raman data permitted structural information on the compounds present (hematite was identified as the main pigment, whereas calcite and gypsum are the main components of the substrate layer, as well as of the accretions that covered the pigments) to be obtained, while the quantitative values obtained by SEM were suitable for the use of Ca as internal reference during LA-ICPMS analysis. However, it was this latter technique that provided the most relevant data for fingerprinting purposes. The potential of this technique for obtaining spatially resolved information allowed the multielement quantitative analysis of the pigment layer, in spite of the presence of superficial accretions. The sensitivity of the technique permitted the determination of more than 40 elements present in a wide concentration range (from microgram per gram to 10% level) with minimum sample consumption (approximately 900 ng for each sample, corresponding to five replicates). Finally, in order to establish significant differences, only those elements showing a high correlation with Fe (As, Co, Mo, Sb, Tl, and Zr, in this case) were selected, as it is expected that these were truly present in the original pigment, while others could have migrated into the pigment layer throughout time. By using this information, it seems feasible to discriminate between various paint pots, as demonstrated for the samples under investigation.

Determination of trace elements in otoliths of chum salmon Oncorhynchus keta by laser ablation-ICP-mass spectrometry

Trace element levels in the otoliths of chum salmon Oncorhynchus keta were examined by means of laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS). A close linear relationship in the Sr/Ca ratios between X-ray analysis with an electron microprobe (EPMA) and LA-ICPMS analysis was found, suggesting that the latter technique could be used to distinguish the marine and freshwater life phases. Mg, Zn, Ba and Sr concentrations of the otoliths differed between the freshwater and seawater growth zones. Mg and Zn concentrations in the freshwater growth zone were significantly higher than those in the seawater growth zone, while Sr and Ba concentration s in the former were significantly lower than in the latter. The relationship between Sr concentration and Mg, Zn, and Ba concentrations at each ablation showed significant correlations. These results suggest that trace element compositions may reflect differences between freshwater and seawater environmental conditions.

Application of laser ablation ICPMS to trace the environmental history of chum salmon Oncorhynchus keta

Trace element levels in otoliths of chum salmon Oncorhynchus keta were examined by means of laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS). A close linear relationship in the Sr:Ca ratios between EPMA (X-ray analysis with an electron microprobe) and LA-ICPMS analyses was found (p<0.0001), suggesting that the latter technique could be used to separate the marine and freshwater life phases. Mg:Ca, Cr:Ca, Zn:Ca and Ba:Ca ratios in either the core region or the oceanic growth zone of the otoliths varied among sites. These differences suggest that elemental compositions may reflect environmental variability among spawning (breeding) or habitat sites. Thus, those element ratios demonstrate the potential to be used to distinguish between fish spawning (breeding) sites and habitats for this species of salmon.