Isotopic signatures reveal zinc cycling in the natural habitat of hyperaccumulator Dichapetalum gelonioides subspecies from Malaysian Borneo.

BACKGROUND: Some subspecies of Dichapetalum gelonioides are the only tropical woody zinc (Zn)-hyperaccumulator plants described so far and the first Zn hyperaccumulators identified to occur exclusively on non-Zn enriched 'normal' soils. The aim of this study was to investigate Zn cycling in the parent rock-soil-plant interface in the native habitats of hyperaccumulating Dichapetalum gelonioides subspecies (subsp. pilosum and subsp. sumatranum). We measured the Zn isotope ratios (δ66Zn) of Dichapetalum plant material, and associated soil and parent rock materials collected from Sabah (Malaysian Borneo). RESULTS: We found enrichment in heavy Zn isotopes in the topsoil (δ66Zn 0.13 ‰) relative to deep soil (δ66Zn -0.15 ‰) and bedrock (δ66Zn -0.90 ‰). This finding suggests that both weathering and organic matter influenced the Zn isotope pattern in the soil-plant system, with leaf litter cycling contributing significantly to enriched heavier Zn in topsoil. Within the plant, the roots were enriched in heavy Zn isotopes (δ66Zn ~ 0.60 ‰) compared to mature leaves (δ66Zn ~ 0.30 ‰), which suggests highly expressed membrane transporters in these Dichapetalum subspecies preferentially transporting lighter Zn isotopes during root-to-shoot translocation. The shoots, mature leaves and phloem tissues were enriched in heavy Zn isotopes (δ66Zn 0.34-0.70 ‰) relative to young leaves (δ66Zn 0.25 ‰). Thisindicates that phloem sources are enriched in heavy Zn isotopes relative to phloem sinks, likely because of apoplastic retention and compartmentalization in the Dichapetalum subspecies. CONCLUSIONS: The findings of this study reveal Zn cycling in the rock-soil-plant continuum within the natural habitat of Zn hyperaccumulating subspecies of Dichapetalum gelonioides from Malaysian Borneo. This study broadens our understanding of the role of a tropical woody Zn hyperaccumulator plant in local Zn cycling, and highlights the important role of leaf litter recycling in the topsoil Zn budget. Within the plant, phloem plays key role in Zn accumulation and redistribution during growth and development. This study provides an improved understanding of the fate and behaviour of Zn in hyperaccumulator soil-plant systems, and these insights may be applied in the biofortification of crops with Zn.

Copper-64 based radiopharmaceuticals for brain tumors and hypoxia imaging.

INTRODUCTION: The most common and aggressive primary malignancy of the central nervous system is Glioblastoma that, as a wide range of malignant solid tumor, is characterized by extensive hypoxic regions. A great number of PET radiopharmaceuticals have been developed for the identification of hypoxia in solid tumors, among these, we find copper-based tracers. The aim of the current review paper was to provide an overview of radiocopper compounds applied for preclinical and clinical research in brain tumors and hypoxia imaging or therapy. EVIDENCE ACQUISITION: Copper offers a wide variety of isotopes, useful for nuclear medicine applications, but only 64Cu and 67Cu are under the spotlight of the scientific community since being good candidates for theranostic applications. Between the two, 64Cu availability and production cost have attracted more interest of the scientific community. EVIDENCE SYNTHESIS: In order to better understand the application of copper-bis thiosemicarbazones in hypoxia imaging, an overview of the role of hypoxia in cancer, existing non-imaging and imaging techniques for hypoxia identification and promising future avenues regarding hypoxia is necessary. Different proposed uptake mechanisms of [64Cu][Cu(ATSM)] inside the cell will be discussed and other 64Cu-based tracers for brain tumors described. CONCLUSIONS: Among radio copper compounds [64Cu][Cu(ATSM)] is the most studied radiopharmaceutical for imaging and treatment of brain tumors. Experimental evidence suggested that [64Cu][Cu(ATSM)] could be more appropriately considered as a marker of over-reduced intracellular state rather than a pure hypoxia agent. Moreover, preliminary clinical data suggested that [64Cu]CuCl2 can be a potentially useful diagnostic agent for malignancies of the central nervous system (CNS).

Isotopically Enriched Tracers and Inductively Coupled Plasma Mass Spectrometry Methodologies to Study Zinc Supplementation in Single-Cells of Retinal Pigment Epithelium in Vitro.

Mass spectrometry-based techniques, such as inductively coupled plasma mass spectrometry (ICPMS) and laser ablation (LA) ICPMS, combined with an isotope pattern deconvolution mathematical tool are proposed for a better understanding of supplementation studies in cultured cells. An in vitro model of human retinal pigment epithelium (HRPEsv) cells was treated with different concentrations (0-150 µm Zn, 1 mL) of enriched stable isotope tracers of Zn in the form of sulfate and/or gluconate. Supplementations with t68ZnSO4 or t70Zn-gluconate alone and in combination (1:1 molar ratio) were investigated to evaluate the exogenous contribution and distribution of Zn in the treated cells. In order to obtain not only the Zn concentration for a cell population (mineralized cells) but also single cell information about the contribution of exogenous Zn and their distribution within micrometer cells structures, LA-ICPMS was employed to directly analyze cryopreserved cells. natZn, t68Zn, and t70Zn molar fraction images obtained from cells and cell aggregates allowed confirming the uptake of exogenous Zn by HRPEsv cells, being t68Zn and t70Zn molar fractions close to 1 in the cell nuclei. Under the selected experimental conditions tested (24 h treatments), no significant differences were obtained in the Zn distribution depending on its chemical form.

Experimental Determination of Zinc Isotope Fractionation in Complexes with the Phytosiderophore 2'-Deoxymugeneic Acid (DMA) and Its Structural Analogues, and Implications for Plant Uptake Mechanisms.

The stable isotope signatures of zinc and other metals are increasingly used to study plant and soil processes. Complexation with phytosiderophores is a key reaction and understanding the controls of isotope fractionation is central to such studies. Here, we investigated isotope fractionation during complexation of Zn2+ with the phytosiderophore 2'-deoxymugeneic acid (DMA), and with three commercially available structural analogues of DMA: EDTA, TmDTA, and CyDTA. We used ion exchange chromatography to separate free and complexed zinc, and identified appropriate cation exchange resins for the individual systems. These were Chelex-100 for EDTA and CyDTA, Amberlite CG50 for TmDTA and Amberlite IR120 for DMA. With all the ligands we found preferential partitioning of isotopically heavy zinc in the complexed form, and the extent of fractionation was independent of the Zn:ligand ratio used, indicating isotopic equilibrium and that the results were not significantly affected by artifacts during separation. The fractionations (in ‰) were +0.33 ± 0.07 (1σ, n = 3), + 0.45 ± 0.02 (1σ, n = 2), + 0.62 ± 0.05 (1σ, n = 3) and +0.30 ± 0.07 (1σ, n = 4) for EDTA, TmDTA, CyDTA, and DMA, respectively. Despite the similarity in Zn-coordinating donor groups, the fractionation factors are significantly different and extent of fractionation seems proportional to the complexation stability constant. The extent of fractionation with DMA agreed with observed fractionations in zinc uptake by paddy rice in field experiments, supporting the possible involvement of DMA in zinc uptake by rice.

High Precision Zinc Stable Isotope Measurement of Certified Biological Reference Materials Using the Double Spike Technique and Multiple Collector-ICP-MS.

Biological reference materials with well-characterised stable isotope compositions are lacking in the field of 'isotope biochemistry', which seeks to understand bodily processes that rely on essential metals by determining metal stable isotope ratios. Here, we present Zn stable isotope data for six biological reference materials with certified trace metal concentrations: fish muscle, bovine muscle, pig kidney, human hair, human blood serum and human urine. Replicate analyses of multiple aliquots of each material achieved reproducibilities (2sd) of 0.04-0.13‰ for δ66/64Zn (which denotes the deviation of the 66Zn/64Zn ratio of a sample from a pure Zn reference material in parts per 1000). This implies only very minor isotopic heterogeneities within the samples, rendering them suitable as quality control materials for Zn isotope analyses. This endorsement is reinforced by (i) the close agreement of our Zn isotope data for two of the samples (bovine muscle and human blood serum) to previously published results for different batches of the same material and (ii) the similarity of the isotopic data for the samples (δ66/64Zn ≈ -0.8 to 0.0‰) to previously published Zn isotope results for similar biological materials. Further tests revealed that the applied Zn separation procedure is sufficiently effective to enable accurate data acquisition even at low mass resolving power (M/ΔM ≈ 400), as measurements and analyses conducted at much higher mass resolution (M/ΔM ≈ 8500) delivered essentially identical results.

Copper and zinc isotope ratios in human bone and enamel.

OBJECTIVES: Here, we report Cu and Zn isotope ratios of bones and teeth of French people from various historical periods with the aim to understand how Cu and Zn isotope ratios of bone, a tissue that is continuously remodeled throughout life but that is prone to post-mortem diagenesis, compare with that of tooth enamel, a tissue that forms once during childhood but that is more resistant to diagenesis. Specifically, we examine (1) the potential existence of sex-related differences in the Cu isotope ratios (represented as δ65 Cu) in the tooth enamel of identified men and women, and (2) a decrease of Zn isotope delta ratios (represented as δ66 Zn) related to the increase of meat and fish consumption during the 20th century. METHODS: Four series of material were studied: the archeological population of Saint-Laurent de Grenoble (17th -18th centuries AD), an anatomical collection of skulls (19th century AD), a contemporary anatomical collection of bones never buried, and contemporary teeth samples. The metals were purified by liquid chromatography and their isotopic ratios measured by means of multicollector inductively coupled plasma mass spectrometry. RESULTS: We describe a clear offset between bone and tooth enamel for Zn isotope ratios, as previously observed in animals. There is a similar offset for Cu isotope ratios. We did not observe any difference between the δ65 Cu values of men and women when looking at dental enamel. For the contemporary samples, the δ66 Zn values of bioapatite decreased, which might be explained by the increase of animal product consumption among the French people during this period, notably when the access to seafood became widespread. CONCLUSIONS: Our study demonstrates that the Cu and Zn isotope compositions of dental enamel are promising tools for childhood diet reconstruction. Meanwhile, the Cu isotope ratio of tooth enamel is unlikely to be useful for the identification of biological sex, even in the case of populations with early menarche. Further works are needed to understand the relationships between trophic level and Zn isotope ratios of human remains.

Zn Isotope Fractionation during Sorption onto Kaolinite.

In this study, we quantify zinc isotope fractionation during its sorption onto kaolinite, by performing experiments under various pH, ionic strength, and total Zn concentrations. A systematic enrichment in heavy Zn isotopes on the surface of kaolinite was measured, with Δ(66)Znadsorbed-solution ranging from 0.11‰ at low pH and low ionic strength to 0.49‰ at high pH and high ionic strength. Both the measured Zn concentration and its isotopic ratio are correctly described using a thermodynamic sorption model that considers two binding sites: external basal surfaces and edge sites. Based on this modeling approach, two distinct Zn isotopic fractionation factors were calculated: Δ(66)Znadsorbed-solution = 0.18 ± 0.06‰ for ion exchange onto basal sites, and Δ(66)Znadsorbed-solution = 0.49 ± 0.06‰ for specific complexation onto edge sites. These two distinct factors indicate that Zn isotope fractionation is dominantly controlled by the chemical composition of the solution (pH, ionic strength).

Earthworm Uptake Routes and Rates of Ionic Zn and ZnO Nanoparticles at Realistic Concentrations, Traced Using Stable Isotope Labeling.

The environmental behavior of ZnO nanoparticles (NPs), their availability to, uptake pathways by, and biokinetics in the earthworm Lumbricus rubellus were investigated using stable isotope labeling. Zinc isotopically enriched to 99.5% in (68)Zn ((68)Zn-E) was used to prepare (68)ZnO NPs and a dissolved phase of (68)Zn for comparison. These materials enabled tracing of environmentally relevant (below background) NP additions to soil of only 5 mg (68)Zn-E kg(-1). Uptake routes were isolated by introducing earthworms with sealed and unsealed mouthparts into test soils for up to 72 h. The Zn isotope compositions of the soils, pore waters and earthworms were then determined using multiple collector inductively coupled plasma mass spectrometry. Detection and quantification of (68)Zn-E in earthworm tissue was possible after only 4 h of dermal exposure, when the uptake of (68)Zn-E had increased the total Zn tissue concentration by 0.03‰. The results demonstrate that at these realistic exposure concentrations there is no distinguishable difference between the uptake of the two forms of Zn by the earthworm L. rubellus, with the dietary pathway accounting for ∼95% of total uptake. This stands in contrast to comparable studies where high dosing levels were used and dermal uptake is dominant.

Early Archean serpentine mud volcanoes at Isua, Greenland, as a niche for early life.

The Isua Supracrustal Belt, Greenland, of Early Archean age (3.81-3.70 Ga) represents the oldest crustal segment on Earth. Its complex lithology comprises an ophiolite-like unit and volcanic rocks reminiscent of boninites, which tie Isua supracrustals to an island arc environment. We here present zinc (Zn) isotope compositions measured on serpentinites and other rocks from the Isua supracrustal sequence and on serpentinites from modern ophiolites, midocean ridges, and the Mariana forearc. In stark contrast to modern midocean ridge and ophiolite serpentinites, Zn in Isua and Mariana serpentinites is markedly depleted in heavy isotopes with respect to the igneous average. Based on recent results of Zn isotope fractionation between coexisting species in solution, the Isua serpentinites were permeated by carbonate-rich, high-pH hydrothermal solutions at medium temperature (100-300 °C). Zinc isotopes therefore stand out as a pH meter for fossil hydrothermal solutions. The geochemical features of the Isua fluids resemble the interstitial fluids sampled in the mud volcano serpentinites of the Mariana forearc. The reduced character and the high pH inferred for these fluids make Archean serpentine mud volcanoes a particularly favorable setting for the early stabilization of amino acids.

Soil (microbial) disturbance affect the zinc isotope biogeochemistry but has little effect on plant zinc uptake.

Zinc (Zn) is an important micronutrient but can be toxic at elevated concentrations. We conducted an experiment to test the effect of plant growth and soil microbial disturbance on Zn in soil and plants. Pots were prepared with and without maize and in an undisturbed soil, a soil that was disturbed by X-ray sterilization and a soil that was sterilized but reconditioned with the original microbiome. The Zn concentration and isotope fractionation between the soil and the soil pore water increased with time, which is probably due to physical disturbance and fertilization. The presence of maize increased the Zn concentration and isotope fractionation in pore water. This was likely related to the uptake of light isotopes by plants and root exudates that solubilized heavy Zn from the soil. The sterilization disturbance increased the concentration of Zn in the pore water, because of abiotic and biotic changes. Despite a threefold increase in Zn concentration and changes in the Zn isotope composition in the pore water, the Zn content and isotope fractionation in the plant did not change. These results have implications for Zn mobility and uptake in crop plants and are relevant in terms of Zn nutrition.

Microanalytical isotope ratio measurements and elemental mapping using laser ablation ICP-MS for tissue thin sections: zinc tracer studies in rats.

The kinetics of zinc absorption, metabolism and excretion is extensively studied by nutritionists. Stable isotopes of zinc can be used to identify body zinc compartments that have different turnover kinetics. Since the compartments might belong to physiological subsections of different organs, there is a need for microsampling analysis to determine isotope ratios of the trace element zinc in tissue samples. Here, we study the feasibility to use laser ablation coupled to quadrupole ICP-MS for the determination of zinc tracers given to rats at different time points with the aim to generate isotope ratio bioimages of heart tissue. A double tracer ((70)Zn and (67)Zn) experiment with rats was designed to label the exchangeable zinc pool as well as the stable zinc pool. The isotope ratios determined by laser ablation ICP-MS were evaluated by additional measurements of tissue digests. Accumulated tracers which made up more than 0.1% of total zinc could be identified in the tissues of the treated rats. It was established that at least 50 measurements from the microsampling were necessary to distinguish between controls and a tracer treated rat resulting in reduced resolution of the bioimage. With the parameters used, features in the tissue thin sections of at least 250 µm(2) in size are necessary to detect the incorporation of a tracer. When different time points have to be measured, higher precisions are required and therefore a larger area needs to be ablated (1 mm(2)). Using the bioimages and pool measurements from one physiological feature, it was possible to show that the aorta cell walls incorporate the zinc tracer at the different time points.

Fractionation of stable zinc isotopes in the zinc hyperaccumulator Arabidopsis halleri and nonaccumulator Arabidopsis petraea.

Zn isotope fractionation may provide new insights into Zn uptake, transport and storage mechanisms in plants. It was investigated here in the Zn hyperaccumulator Arabidopsis halleri and the nonaccumulator A. petraea. Plant growth on hydroponic solution allowed us to measure the isotope fractionation between source Zn (with Zn(2+) as dominant form), shoot and root. Zn isotope mass balance yields mean isotope fractionation between plant and source Zn Δ(66)Zn(in-source) of -0.19 ± 0.20‰ in the nonaccumulator and of -0.05 ± 0.12‰ in the hyperaccumulator. The isotope fractionation between shoot Zn and bulk Zn incorporated (Δ(66)Zn(shoot-in)) differs between the nonaccumulator and the hyperaccumulator and is function of root-shoot translocation (as given by mass ratio between shoot Zn and bulk plant Zn). The large isotope fractionation associated with sequestration in the root (0.37‰) points to the binding of Zn(2+) with a high affinity ligand in the root cell. We conclude that Zn stable isotopes may help to estimate underground and aerial Zn storage in plants and be useful in studying extracellular and cellular mechanisms of sequestration in the root.

Cyclotron-produced 68Ga from enriched 68Zn foils.

The growing need and limited availability of generator produced 68Ga (T1/2 = 68 min) for PET has provided the impetus for alternative, high output, 68Ga production routes such as charge particle activation of enriched 68Zn using PET cyclotrons. The work presents a rapid production method for clinically useful 68Ga for radiolabeling. The focus is also to expand the production capacity of cyclotron solid target-produced 68Ga over generator produced and liquid solutions targets by using enriched 68Zn-foils that minimizes target preparation.

Zinc isotopic composition of particulate matter generated during the combustion of coal and coal + tire-derived fuels.

Atmospheric Zn emissions from the burning of coal and tire-derived fuel (TDF) for power generation can be considerable. In an effort to lay the foundation for tracking these contributions, we evaluated the Zn isotopes of coal, a mixture of 95 wt % coal + 5 wt % TDF, and the particulate matter (PM) derived from their combustion in a power-generating plant. The average Zn concentrations and δ(66)Zn were 36 mg/kg and 183 mg/kg and +0.24‰ and +0.13‰ for the coal and coal + TDF, respectively. The δ(66)Zn of the PM sequestered in the cyclone-type mechanical separator was the lightest measured, -0.48‰ for coal and -0.81‰ for coal+TDF. The δ(66)Zn of the PM from the electrostatic precipitator showed a slight enrichment in the heavier Zn isotopes relative to the starting material. PM collected from the stack had the heaviest δ(66)Zn in the system, +0.63‰ and +0.50‰ for the coal and coal + TDF, respectively. Initial fractionation during the generation of a Zn-rich vapor is followed by temperature-dependent fractionation as Zn condenses onto the PM. The isotopic changes of the two fuel types are similar, suggesting that their inherent chemical differences have only a secondary impact on the isotopic fractionation process.

Experimental and theoretical investigation of isotope fractionation of zinc between aqua, chloro, and macrocyclic complexes.

This work reports on the chemical isotope fractionation of Zn(II) by a solvent extraction method with the crown ether dicyclohexano-18-crown-6. The (m)Zn/(64)Zn ratios (m = 66, 67, and 68) were analyzed by multiple-collector inductively coupled plasma mass spectrometry. The relative deviations of the (66)Zn/(64)Zn ratios relative to the unprocessed material (delta(66)Zn) was determined to be -0.51 to -0.32 in the acidity region 1.0-6.0 mol dm(-3) (M) HCl. The acidity dependence of delta(m)Zn was explained by the isotope exchange reactions between Zn(II) species (Zn(2+), ZnCl(+), ZnCl(2), ZnCl(3)(-), and ZnCl(4)(2-)) and the mole fractions of them. The magnitude of delta(m)Zn due to the related Zn(II) species estimated by quantum chemical calculations was in agreement with delta(m)Zn experimentally obtained. Contribution of nuclear field shift to the isotope fractionation was estimated to be less than 10% of delta(m)Zn by quantum chemical calculations.

Studying the cellular distribution of highly phototoxic platinated metalloporphyrins using isotope labelling.

Novel tetraplatinated metalloporphyrin-based photosensitizers (PSs) are reported, which show excellent phototoxic indexes (PIs) up to 5800 against HeLa cells, which is, to the best of our knowledge, the highest value reported for any porphyrin so far. Furthermore, 67Zn isotope labelling allowed the determination of the ratio of zinc to platinum inside the cells using ICP-MS.

A QM/MM approach to interpreting 67Zn solid-state NMR data in zinc proteins.

We present here a (67)Zn solid-state NMR investigation of Zn(2+) substituted rubredoxin. The sample has been prepared as both a dry powder and a frozen solution to determine the effects of static disorder on the NMR line shape. Low-temperature experiments have been performed at multiple fields to determine the relative contributions to the NMR line shape from the electric field gradient and the anisotropic shielding tensors. Finally we present the theoretical interpretation of the experimental results utilizing a combined quantum mechanical molecular mechanics (QM/MM) approach. Theory predicts a sizable contribution from anisotropic shielding as compared with previously examined model systems. This is in good agreement with the experimental data.

Variation in the isotopic composition of zinc in the natural environment and the use of zinc isotopes in biogeosciences: a review.

Zinc (Zn) is a trace element that is, as a building block in various enzymes, of vital importance for all living organisms. Zn concentrations are widely determined in dietary, biological and environmental studies. Recent papers report on the first efforts to use stable Zn isotopes in environmental studies, and initial results point to significant Zn isotope fractionation during various biological and chemical processes, and thus highlight their potential as valuable biogeochemical tracers. In this article, we discuss the state-of-the-art analytical methods for isotopic analysis of Zn and the procedures used to obtain accurate Zn isotope ratio results. We then review recent applications of Zn isotope measurements in environmental and life sciences, emphasizing the mechanisms and causes responsible for observed natural variation in the isotopic composition of Zn. We first discuss the Zn isotope variability in extraterrestrial and geological samples. We then focus on biological processes inducing Zn isotope fractionation in plants, animals and humans, and we assess the potential of Zn isotope ratio determination for elucidating sources of atmospheric particles and contamination. Finally, we discuss possible impediments and limitations of the application of Zn isotopes in (geo-) environmental studies and provide an outlook regarding future directions of Zn isotope research.

Development of a method for assessing the relative contribution of waterborne and dietary exposure to zinc bioaccumulation in Daphnia magna by using isotopically enriched tracers and ICP-MS detection.

In order to study the effect of anthropogenic substances on freshwater and marine ecosystems and to develop methods to derive water-quality criteria, ecotoxicological testing is required. While toxicity assessments are traditionally based on dissolved metal concentrations, assuming that toxicity is caused by waterborne metal only, it was recently pointed out that also the dietary exposure route should be carefully considered and interpreted in regulatory assessments of zinc. In this context, the aim of this experimental study was to develop a method which allows the uptake of waterborne and dietary zinc by Daphnia magna and the interaction between both exposure routes to be studied. Therefore, the setup of a dual isotopic tracer study was required. During several days, daphnids were exposed to 67Zn and 68Zn via the dietary and the waterborne routes, respectively, and after several time intervals the daphnids were sampled and subjected to isotopic analysis by means of inductively coupled plasma mass spectrometry (ICP-MS). In order to obtain reliable and accurate results for zinc, special care was taken to prevent contamination and to deal with the spectral interferences traditionally hindering the determination of zinc. The figures of merit of both a quadrupole-based ICP-MS instrument equipped with a dynamic reaction cell, and a sector field ICP-MS unit were studied, and it was concluded that by using a sector field mass spectrometer operated at medium mass resolution all interferences could be overcome adequately. Although the set-up of the exposure experiments seems to be rather simple at first sight, it was shown in this work that several (dynamic) variables can have an influence on the results obtained and on the subsequent data interpretation. The importance of these confounding factors was examined, and on the basis of preliminary calculations it became clear that not only the isotopic composition of the daphnids has to be studied--adequate monitoring of the isotopic composition of the dissolved phase and the algae during the exposure of the daphnids is also required to accurately discriminate between uptake from water and from food.

Production of Ga-68 with a General Electric PETtrace cyclotron by liquid target.

PURPOSE: In recent years the use of 68Ga (t1/2 = 67.84 min, ß+: 88.88%) for the labelling of different PET radiopharmaceuticals has significantly increased. This work aims to evaluate the feasibility of the production of 68Ga via the 68Zn(p,n)68Ga reaction by proton irradiation of an enriched zinc solution, using a biomedical cyclotron, in order to satisfy its increasing demand. METHODS: Irradiations of 1.7 Msolution of 68Zn(NO3)2 in 0.2 N HNO3 were conducted with a GE PETtrace cyclotron using a slightly modified version of the liquid target used for the production of fluorine-18. The proton beam energy was degraded to 12 MeV, in order to minimize the production of 67Ga through the68Zn(p,2n)67Ga reaction. The product's activity was measured using a calibrated activity meter and a High Purity Germanium gamma-ray detector. RESULTS: The saturation yield of68Ga amounts to (330 ±â€¯20) MBq/µA, corresponding to a produced activity of68Ga at the EOB of (4.3 ±â€¯0.3) GBq in a typical production run at 46 µA for 32 min. The radionuclidic purity of the68Ga in the final product, after the separation, is within the limits of the European Pharmacopoeia (>99.9%) up to 3 h after the EOB. Radiochemical separation up to a yield not lower than 75% was obtained using an automated purification module. The enriched material recovery efficiency resulted higher than 80-90%. CONCLUSIONS: In summary, this approach provides clinically relevant amounts of68Ga by cyclotron irradiation of a liquid target, as a competitive alternative to the current production through the68Ge/68Ga generators.