Selenium Species Research Articles

Assessment of dietary Selenium and its role in Mercury fate in cultured fish rainbow trout with two sustainable aquafeeds

This study enhances the current limited understanding of the interaction between mercury (Hg) and selenium (Se) species in fish. Rainbow trout (Oncorhynchus mykiss), a model aquaculture fish, was exposed to Hg and Se species through controlled dietary conditions. Over a 6-month feeding trial, the impact of dietary Se on Hg bioaccumulation in fish, including flesh, brain, and liver, was tracked. Twelve dietary conditions were tested, including plant-based diets (0.25 µgSe g−1) and tuna byproduct diets (0.25 µgHg g−1, 8.0 µgSe g−1) enriched with methylmercury and/or Se as selenite or selenomethionine. The tuna byproduct diet resulted in lower Hg levels than the plant-based diets, with muscle Hg content below the European Commission's safe threshold. This study highlights the significant impact of specific Se compounds in the diet, particularly from tuna-based aquafeed, on Hg bioaccumulation. These promising results provide a strong recommendation for future use of fisheries byproducts in sustainable aquafeeds.

Influences of sources and weather dynamics on atmospheric deposition of Se species and other trace elements

Abstract. Atmospheric deposition is an important source of the micronutrient selenium for terrestrial ecosystems and food chains. However, the factors determining the total concentrations and chemical forms (speciation) of selenium in atmospheric deposition remain poorly understood. Here, aerosol samples were collected weekly over 5 years at Pic du Midi Observatory (French Pyrenees), alongside highly temporally resolved samples of aerosols, precipitation, and cloud water taken during a 2-month campaign. Firstly, measurements of selenium, other elements, and water isotopes were combined with sophisticated modelling approaches (aerosol–chemistry–climate SOCOL-AERv2 model and air parcel backward trajectories and Lagrangian moisture source analyses). Aerosol selenium measurements agreed well with SOCOL-AERv2-predicted values, and interestingly, higher fluxes of selenium and other elements were associated with deep convective activity during thunderstorms, highlighting the importance of local cloud dynamics in high deposition fluxes. Our results further indicate the coupling of element and water cycles from source to cloud formation, with decoupling during precipitation due to below-cloud scavenging. Secondly, selenium speciation was investigated in relation to sulfur speciation, organic composition, and moisture sources. While in the 5-year aerosol series, selenite (SeIV) was linked to anthropogenic source factors, in wet deposition it was related to pH and Atlantic moisture sources. We also report an organic selenium fraction, tracing it back to a marine biogenic source in both aerosols and wet deposition. With a comprehensive set of observations and model diagnostics, our study underscores the role of weather system dynamics alongside source contributions in explaining the atmospheric supply of trace elements to surface environments.

Synthesis of bis‐Naphthol based Organoselenium Antioxidants as Efficient Inhibitors against Biofilms

AbstractIn the present study, synthesis of bis‐naphthol based organoselenium compounds has been described. The synthetic strategy involves electrophilic aromatic addition of alkyl/aryl selenium species at the electron rich center of 2,7‐dihydroxynaphthalene. The reaction with electrophilic selenylating reagents in situ generated by potassium persulphate and diselenides produced desired selenides. Synthesized compounds were studied for their glutathione peroxidase (GPx)‐like antioxidant activities using thiophenol assay. It was observed that all compounds exhibited greater GPx‐like antioxidant activity than diphenyl diselenide used as reference. Further, these GPx mimics were introduced for their antibacterial properties against biofilm formation by Bacillus subtilis and Pseudomonas aeruginosa. To support experimental details, molecular docking studies were also performed to elucidate in silico interactions between the active sites of proteins TsaA and LasR found in Bacillus subtilis and Pseudomonas aeruginosa, respectively. The minimum inhibitory concentration assay was performed for all the antioxidants against Bacillus subtilis and Pseudomonas aeruginosa. Additionally, hemolytic assay has also been carried out to check the impact on red blood cells. Cytotoxicity assessments of antioxidants have also been carried using MTT assay.

Molecular Mechanisms of the Effects of Sodium Selenite on the Growth, Nutritional Quality, and Species of Organic Selenium in Dandelions

Selenium (Se) is an essential trace element for the human body, and its dietary deficiency has been a widespread issue globally. Vegetables serve as a significant source of dietary Se intake, with organic Se derived from plants being safer than inorganic Se. In the present study, Taraxacum mongolicum plants were treated with various concentrations of Na2SeO3. The results showed that as the concentration of Na2SeO3 increased, the chlorophyll content of dandelion seedlings decreased at high concentrations, and the content of soluble sugars, soluble proteins, flavonoids, total phenols, and Vc all increased. The application of Na2SeO3 at concentrations ranging from 0 to 4 mg/L resulted in a reduction in plant malondialdehyde content and an enhancement in the activity of antioxidant enzymes. Following the Na2SeO3 treatment, five Se species were identified in the seedlings, Se4+, Se6+, selenocysteine, selenomethionine, and methylselenocysteine. Notably, selenomethionine emerged as the primary organic Se species in the shoots of dandelion. Transcriptome analysis revealed that ABC11b, PTR4, MOCOS, BAK1, and CNGC1 were involved in the absorption, transport, and storage of Se in dandelion, and C7317 was involved in the scavenging of reactive oxygen species. This study complements the understanding of the possible molecular mechanisms involved in the absorption and transformation of organic Se by plants, thereby providing a theoretical foundation for the biofortification of dandelion with Se in crops.

Metal‐free regioselective selenylation of β‐napthol derivatives promoted by trichloroisocyanuric acid

AbstractA new approach for synthesizing selenylated naphthalene derivatives is described herein, employing trichloroisocyanuric acid (TCCA) as the oxidizing agent. The developed protocol yielded 18 compounds, with yields ranging from 32 % to 90 %. Additionally, the reaction was conducted under mild conditions, utilizing ethanol as the solvent at room temperature, demonstrating good atom economy. The key aspect of the protocol is the in situ generation of electrophilic selenium species through the reaction of diorganyl diselenides and TCCA.

Characterization of Selenium Speciation in Se-Enriched Crops: Crop Selection Approach.

Accurately quantifying selenium (Se) speciation and transformation in Se-enriched crops is highly significant for human health. The investigation of Se species in Se-enriched crops involves assessing the enrichment of both organic and inorganic Se species, considering their plant families and edible parts. The staple crops of rice, corn, and wheat showed no or less inorganic Se with the increase of total Se; however, potatoes expressed a proportion of selenate [Se(VI)]. In addition, the organic Se proportions in Se-enriched crops of Cruciferous, Brassicaceae, and Umbelliferae plant families were relatively lower than the proportion of inorganic Se. Concurrently, the edible parts of the Se-enriched gramineous or cereal crops enriched with organic Se and crops with fruit, stem, leaf, and root as edible parts contain the maximum percentage of organic Se with a certain proportion of inorganic Se. This study contributes to a sparse body of literature by meticulously discerning appropriate Se-enriched crop selection through a comprehensive evaluation of Se speciation and its organic and inorganic accumulation potential.

Investigation of selenium and selenium species in Cardamine violifolia using in vitro digestion coupled with a Caco-2 cell monolayer model

Inadequate Se intake can enhance vulnerability to certain health risks, with supplementation lessening these risks. This study investigated the bioavailability of Se and Se species in five Se compounds and in Se-rich Cardamine violifolia using in vitro digestion coupled with a Caco-2 cell monolayer model, which enabled the study of Se transport and uptake. Translocation results showed that SeCys2 and MeSeCys had high translocation rates in C. violifolia leaves (CVLs). The uptake rate of organic Se increased with time, and MeSeCys exhibited a higher uptake rate than that for SeCys2 and SeMet. The translocation mechanisms of SeMet, Se(IV), and Se(VI) were passive transport, whereas those of SeCys2 and MeSeCys were active transport. The bioavailability of organic Se was higher than that of inorganic Se, with a total Se bioavailability in CVLs of 49.11 %. This study would provide a theoretical basis for the application of C. violifolia in the functional food.

Diffusive transport of selenium oxyanions in compacted natural clays: role of selenium speciation and clay geochemistry

Diffusive transport of selenium oxyanions in compacted natural clays: role of selenium speciation and clay geochemistry

Selenium speciation studies in cancer patients to evaluate the responses of biomarkers of selenium status to different selenium compounds

This work presents the first systematic comparison of selenium (Se) speciation in plasma from cancer patients treated orally with three Se compounds (sodium selenite, SS; L-selenomethionine, SeMet; or Se-methylselenocysteine, MSC) at 400 µg/day for 28 days. The primary goal was to investigate how these chemical forms of Se affect the plasma Se distribution, aiming to identify the most effective Se compound for optimal selenoprotein expression. This was achieved using methodology based on HPLC-ICP-MS after sample preparation/fractionation approaches. Measurements of total Se in plasma samples collected before and after 4 weeks of treatment showed that median total Se levels increased significantly from 89.6 to 126.4 µg kg−1 Se (p < 0.001), particularly when SeMet was administered (190.4 µg kg−1 Se). Speciation studies showed that the most critical differences between treated and baseline samples were seen for selenoprotein P (SELENOP) and selenoalbumin after administration with MSC (p = 5.8 × 10−4) and SeMet (p = 6.8 × 10−5), respectively. Notably, selenosugar-1 was detected in all low-molecular-weight plasma fractions following treatment, particularly with MSC. Two different chromatographic approaches and spiking experiments demonstrated that about 45% of that increase in SELENOP levels (to ~ 8.8 mg L−1) with SeMet is likely due to the non-specific incorporation of SeMet into the SELENOP affinity fraction. To the authors’ knowledge, this has not been reported to date. Therefore, SELENOP is probably part of both the regulated (55%) and non-regulated (45%) Se pools after SeMet administration, whereas SS and MSC mainly contribute to the regulated one.Graphical abstract

Speciation analysis of inorganic selenium in food and water samples utilizing a 2,3-diaminonaphthalene post-synthetic modified magnetic metal–organic framework

In this work, a 2,3-diaminonaphthalene post-synthetic modified magnetic metal–organic framework was fabricated for fast and selective determination of inorganic selenium in real food and water samples. The results exhibited that selenium (IV) is adsorbed by the nano-material at a pH of 2.5, and in this way, selenium (IV) can be quantified selectively. After identifying the nanosorbent with FT-IR, CHNS, XRD, SEM, TEM, VSM, and BET surface analysis, parameters affecting the retention and desorption were optimized. Under optimal conditions, the detection limit of 8 ng/L was achieved for selenium (IV), and the method's precisions were less than 12.5 % intra-day RSD% and < 14.4 % for inter-day RSD%. The highest adsorption capacity was obtained as 264 mg/g. Finally, the desired adsorbent was used to extract and determine selenium species in water samples and total selenium in food samples. One of the most important advantages of the present method is its speed, ease, time-saving, and high accuracy.

Bromide Ion Impurity-Induced Reaction between Selenium(IV) and Acidic Bromate: Prototype of a Cycle with Autocatalytic Behavior.

The selenium(IV)-bromate reaction in an acidic medium using phosphoric acid/phosphate buffer was investigated by UV-vis spectroscopy monitoring the formation of bromine. In an excess of bromate, the absorbance-time curves measured at 450 nm display a characteristic sigmoidal shape having a fairly long induction period, while in the opposite case, when selenium(IV) species is used in excess, the measured data follow the rise and fall behavior. Depending on the excess of Se(IV) the final bromine-containing product is either an elementary bromine or bromide ion. Simultaneous evaluation of the measured kinetic traces clearly indicated that, surprisingly, no direct reaction takes place between the reactants. Instead of that, a trace amount of bromide ion impurity in the stock bromate solution is sufficient to drive the system via the oxidation of the bromide ion by bromate producing elementary bromine followed by the subsequent selenite-bromine reaction reestablishing the bromide ion to open a new cycle. As a result, the concentration of bromide ions increases in a sigmoidal fashion during the course of the reaction unless enough selenium(IV) species is present; hence, the overall synergetic effect observed is the autocatalytic rise of bromide ions. Therefore, the cycle mentioned above may be considered as a prototype of autocatalytic cycles. This observation prompted us to clarify the explicit difference between an autocatalytic cycle and an autocatalytic reaction.

Importance of Elemental Chemical Speciation Studies in Enriched Food: Nutritional Quality, Toxicity, and Economic Improvement

For several reasons, mainly cost and local productivity, the world population does not have access to a balanced diet that contains all the macro and micronutrients necessary to maintain physiological functions for a healthy life. Nutritional education, supplementation, and consuming enriched (or fortified) foods appear as alternatives to supply daily demands and minimize malnutrition. Adding essential elements as salts (e.g., iron, calcium, and zinc) to ready-to-eat processed foods, such as milk, flour, and juices is already adopted in several countries. The choice of the compound to be added, as well as the transport vehicle (foods), must be very well evaluated since the cost, long-term consumption, and bioavailability of the added chemical species are imperative to ensure the nutritional quality of enriched food.1 Another alternative to produce enriched foods is cultivating an enriched medium (Figure 1), adding essential elements to soil or in nutritive solution (hydroponic procedure), irrigating leaves, or immersing seeds.2 In this case, the chemical species used to the enrich food must be absorbed, translocated, and accumulated in the edible part.2 Studies have shown that the iron enrichment of adzuki beans using iron nitrate or iron chloride was unsuccessful since iron inorganic species interact strongly with the antinutrients (tannins or phytates) present in the roots, forming insoluble complexes and preventing their translocation.3 Alternatives found to overcome this obstacle were enrichment by applying iron complexes with EDTA (ethylenediaminetetra-acetic acid)3 or iron nanoparticles, mainly encapsulated.4 The nanoparticle application has been gaining prominence in agriculture, aiming to carry fertilizer, pesticides, and nutrients to stimulate plant growth and increase macro and micronutrient availability and absorption efficiency.5,6 Besides the interaction between essential elements with antinutrients, evaluating the competition between elemental species is important, because synergistic or antagonistic effects can be observed. In both cases, chemical species must interact with other components present in food or cultivation medium, altering its chemical composition when compared to food cultivated in conventional conditions. The antagonistic effect between selenium and mercury was observed in edible mushrooms, while the synergistic effect was observed with lead and selenium.7,8 Finally, it must be evaluated if the enrichment promotes the production of non-bioavailable or toxic species. Regardless of the food enrichment strategy, it is important to highlight the need to identify and quantify the elemental chemical species in the enriched foods by chemical speciation analysis. In the Figure 1 is shown examples of elemental chemical species; they can differ according to their oxidation states, inorganic forms, and organometallic or isotopic composition.9 For chemical speciation studies, initial fractionation steps (e.g., extraction procedures) are carried out; subsequently, chromatographic, or non-chromatographic methods can be used to identify/determine the chemical species. The hyphenation (Figure 1) between separation techniques, mainly chromatography, with high sensitivity detectors, such as inductively coupled plasma mass spectrometry (ICP-MS), is commonly applied.9-11 Nonetheless, extremely creative procedures used in non-chromatographic chemical speciation, working only with chemical reactions and solubility differences, can also be applied to determine chemical species. Non-chromatographic strategies were applied for iron (reaction with hydroxylamine and precipitation with trichloroacetic acid and HCl) and selenium (cloud point extraction) speciation in enriched adzuki sprouts.3 In summary, food enrichment success is closely associated with chemical speciation studies since there are chemical species that will be absorbed in a cultivation medium, as well as the chemical species that are formed during translocation and accumulation, which must be in bioavailable forms, in order to act on the different metabolic systems of the human body, including remedying prevalences. In this scenario, it is imperative to go beyond determining the total concentration of essential elements, since quantifying their species will provide information regarding essentiality and toxicity. Finally, the formation of bioavailable chemical species will add nutritional quality and, consequently, economic benefits that are so essential for countries with specific prevalences to combat in a predominantly agricultural economy.

Different effects of selenium speciation on selenium absorption, selenium transformation and cadmium antagonism in garlic

Currently, planting selenium-rich crops using inorganic selenium such as selenate and selenite is used to address human selenium deficiency problems. In this paper, besides the above two traditional inorganic selenium speciation, we chose a new organic selenium speciation of potassium selenocyanoacetate to investigate the different effects of selenium speciation on selenium absorption, selenium transformation and cadmium antagonism via foliar application. Plantingexperiments showed that the selenium content of garlic bulbs treated with organic selenium was 1.8–3.9 times higher than that of inorganic selenium. Additionally, the absorption and transformation efficiency of organic selenium in garlic was also the highest, reaching over 95 %. Importantly, it was noteworthy that the cadmium content in bulbs treated with organic selenium was significantly lower than the Chinese food safety standard (0.2 mg/kg). Hence, this study provides an efficient organic selenium speciation which is beneficial to meet human selenium requirements and ensure safe utilization of cadmium-contaminated soils.

Systematic characterization of selenium speciation in coal fly ash.

Millions of tons of coal fly ashes (CFAs) are produced annually during coal combustion in the U.S., which are commonly beneficially used in the concrete industry or disposed of in ash ponds. CFAs contain trace amounts of a range of toxic heavy metals including selenium (Se). Because the toxicity of Se is dependent on its speciation, investigating Se speciation in CFAs as affected by coal source and combustion conditions can help understand the related environmental and human health impacts during disposal or beneficial reuse. In this study, a set of representative CFA samples were characterized for Se speciation using synchrotron X-ray absorption spectroscopy (XAS) and micro-X-ray fluorescence spectromicroscopy (μ-XRF/XAS). Se-containing particles were highly heterogeneous, and individual particles might contain multiple oxidation states including Se(0), Se(IV), and Se(VI). Principal component analysis was performed for sample characteristics including Al2O3, SiO2, CaO, FeO, loss on ignition, average particle size, Se concentration, and Se oxidation state. Selective catalytic reduction (SCR), which is used to limit nitrogen oxide (NOx) emissions during coal combustion, was found to be associated with the presence of reduced Se oxidation states, with up to 90% Se(0) observed in samples with SCR. Alongside SCR, FeO content may also influence Se speciation.

Certification of New Selenium-Enriched Yeast and Supplement Reference Materials for Selenomethionine Using Two Independent Measurement Strategies.

Selenium-enriched yeast possesses the unique ability of transforming chemical selenium, such as sodium selenite, into a biologically active form, which mitigates its toxic effects on the human body. The transformation product of this process, selenomethionine, can be safely and effectively absorbed and utilized by the human body; hence, it has been spiked into a selenium-enriched supplement. This study employs two distinct measurement strategies to determine the selenomethionine content in two candidate reference materials, a selenium-enriched yeast powder and supplement, using both organic and inorganic mass spectrometry. The concentrations of selenomethionine in the selenium-enriched yeast were determined using HPLC-ICP-MS and HPLC- ESI-MS/MS, with mass fractions measured at 718 mg SeMet kg-1 and 715 mg SeMet kg-1, respectively. Notably, both methods yielded consistent results for the selenium supplement, with a selenomethionine mass fraction of 59 mg SeMet kg-1. Ultimately, the certified values of these candidate reference materials were determined as 716 mg kg-1 and 59 mg SeMet kg-1 with expanded uncertainties of 36 mg SeMet kg-1 (k = 2) and 5 mg SeMet kg-1 (k = 2), respectively. The development of these candidate reference materials serves as a valuable reference for diverse methods aiming to determine the value of organic selenium speciation in complex food substrates.

A screening for optimal selenium enrichment additives for selenium-enriched fish production: Application of a HPLC-ICP-MS method

The production of selenium-enriched fish contributes to alleviating selenium deficiency for humans. In this study, selenium nanoparticles (SeNPs) comparable in bioavailability to selenomethionine (SeMet), increased SeMet content in O. macrolepis (Onychostoma macrolepis) muscle. Additionally, dietary SeNPs significantly enhanced selenocysteine (SeCys2) and methylselenocysteine (MeSeCys) levels in O. macrolepis muscle. The effect of SeNPs on selenium speciation in grass carp muscle was consistent with O. macrolepis results. SeCys2 and MeSeCys showed antioxidant capacity in HEK293T cells, indicating enhanced health benefits of Se-enriched fish produced using SeNPs. Furthermore, the addition of 0.3 mg/kg SeNPs significantly improved the flesh quality of O. macrolepis by reducing the content of crude fat and heavy metals, as well as increasing the levels of crude protein, eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and the ratio of n-3/n-6 polyunsaturated fatty acids (PUFAs). Therefore, selenium-enriched fish produced from SeNPs is a good source for improving human dietary selenium intake.

Synchrotron speciation of umbilical cord mercury and selenium after environmental exposure in Niigata

The insidious and deadly nature of mercury’s organometallic compounds is informed by two large scale poisonings due to industrial mercury pollution that occurred decades ago in Minamata and Niigata, Japan. The present study examined chemical speciation for both mercury and selenium in a historic umbilical cord sample from a child born to a mother who lived near the Agano River in Niigata. The mother had experienced mercury exposure leading to more than 50 ppm mercury measured in her hair and was symptomatic 9 years prior to the birth. We sought to determine the mercury and selenium speciation in the child’s cord using Hg Lα1 and Se Kα1 high-energy resolution fluorescence detected X-ray absorption spectroscopy, the chemical speciation of mercury was found to be predominantly organometallic and coordinated to a thiolate. The selenium was found to be primarily in an organic form and at levels higher than those of mercury, with no evidence of mercury-selenium chemical species. Our results are consistent with mercury exposure at Niigata being due to exposure to organometallic mercury species.

Speciation of Selenium Nanoparticles and Other Selenium Species in Soil: Simple Extraction Followed by Membrane Separation and ICP-MS Determination.

The application of selenium nanoparticle (SeNP)-based fertilizers can cause SeNPs to enter the soil environment. Considering the possible transformation of SeNPs and the species-dependent toxicity of selenium (Se), accurate analysis of SeNPs and other Se species present in the soil would help rationally assess the potential hazards of SeNPs to soil organisms. Herein, a novel method for speciation of SeNPs and other Se species in soil was established. Under the optimized conditions, SeNPs, selenite, selenate, and seleno amino acid could be simultaneously extracted from the soil with mixtures of tetrasodium pyrophosphate (5 mM) and potassium dihydrogen phosphate (1.2 μM), while inert Se species (mainly metal selenide) remained in the soil. Then, extracted SeNPs can be effectively captured by a nylon membrane (0.45 μm) and quantified by inductively coupled plasma mass spectrometry (ICP-MS). Other extracted Se species can be separated and quantified by high-performance liquid chromatography coupled with ICP-MS. Based on the difference between the total Se contents and extracted Se contents, the amount of metal selenide can be calculated. The limits of detection of the method were 0.02 μg/g for SeNPs, 0.05 μg/g for selenite, selenate, and selenocystine, and 0.25 μg/g for selenomethionine, respectively. Spiking experiments also showed that our method was applicable to real soil sample analysis. The present method contributes to understanding the speciation of Se in the soil environment and further estimating the occurrence and application risks of SeNPs.

Insight into the influence of environmental factors on selenite removal from desulfurization wastewater by NZVI@AC: An experimental and theoretical study

Nano zero-valent iron (NZVI) technology has shown good potential for the treatment of selenium in wastewater. In this study, NZVI was loaded on activated carbon (AC) by carbothermal reduction method to synthesize high-efficiency adsorbent (NZVI@AC). The agglomeration of NZVI was suppressed and its reactivity was improved. The optimum preparation temperature of NZVI@AC (600 °C) was determined by comparing its purity. Moreover, the synergistic effect between the active component (NZVI) and the support (AC) was investigated on the basis of the density functional theory method. The smaller HOMO-LUMO gap (0.87 eV) and charge distribution of NZVI@AC indicated favorable electron transfer and enhanced chemical reactivity. The adsorption and reduction to Se(0)/Se(-II) were elucidated as the underlying mechanisms for the removal of selenite by comparative analysis of the morphological transformation of iron and selenium species. Furthermore, the selenite removal performance of NZVI@AC was investigated on account of the impact of dissolved oxygen and pH values, and the interaction mechanism of these factors was revealed. The decrease of solution pH and dissolved oxygen concentration are effective ways to improve the removal efficiency of selenite.

Unlocking the key role of bentonite fungal isolates in tellurium and selenium bioremediation and biorecovery: Implications in the safety of radioactive waste disposal

Research on eco-friendly bioremediation strategies for mitigating the environmental impact of toxic metals has gained attention in the last years. Among all promising solutions, bentonite clays, to be used as artificial barriers to isolate radioactive wastes within the deep geological repository (DGR) concept, have emerged as effective reservoir of microorganisms with remarkable bioremediation potential. The present study aims to investigate the impact of bentonite fungi in the speciation and mobility of selenium (Se) and tellurium (Te), as natural analogues 79Se and 132Te present in radioactive waste, to screen for those strains with bioremediation potential within the context of DGR. For this purpose, a multidisciplinary approach combining microbiology, biochemistry, and microscopy was performed. Notably, Aspergillus sp. 3A demonstrated a high tolerance to Te(IV) and Se(IV), as evidenced by minimal inhibitory concentrations of >16 and >32 mM, respectively, along with high tolerance indexes. The high metalloid tolerance of Aspergillus sp. 3A is mediated by its capability to reduce these mobile and toxic elements to their elemental less soluble forms [Te(0) and Se(0)], forming nanostructures of various morphologies. Advanced electron microscopy techniques revealed intracellular Te(0) manifesting as amorphous needle-like nanoparticles and extracellular Te(0) forming substantial microspheres and irregular accumulations, characterized by a trigonal crystalline phase. Similarly, Se(0) exhibited a diverse array of morphologies, including hexagonal, irregular, and needle-shaped structures, accompanied by a monoclinic crystalline phase. The formation of less mobile Te(0) and Se(0) nanostructures through novel and environmentally friendly processes by Aspergillus sp. 3A suggests it would be an excellent candidate for bioremediation in contaminated environments, such as the vicinity of deep geological repositories. It moreover holds immense potential for the recovery and synthesis of Te and Se nanostructures for use in numerous biotechnological and biomedical applications.