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Effects of selenium nanoparticles on cadmium uptake, selenium transformation, and metabolomics in Agaricus blazei murill

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Overview

Luo and colleagues investigated the mechanism by which selenium nanoparticles (Se NPs) reduce cadmium content in Agaricus blazei Murill (AbM) fruiting bodies. They found that Se NPs at 50 mg/kg applied to the substrate reduced fruiting-body cadmium by 48.7 to 69.4% across four harvest waves. Background cadmium in AbM grown on uncontaminated substrate (CK) reached 4.2 to 26.0 mg/kg dry basis across four harvests, exceeding the Chinese national standard of 0.2 mg/kg fresh weight (which corresponds to approximately 2 mg/kg dry weight at 90% moisture). Cadmium was predominantly sequestered in the cell wall fraction (82.9 to 95.8% of total). Se NPs transformed selenium into organic forms (selenocysteine, selenomethionine, selenomethylcysteine) in the fruiting body.

Key numbers

Cadmium in AbM fruiting bodies (mg/kg dry basis, mean plus or minus SD, n=6, Table 1):

  • CK (no cadmium added): 4.2 to 26.0 mg/kg across four harvest waves (background cadmium from substrate materials).
  • Cd2 treatment (2 mg/kg cadmium added to substrate): 198.8 to 762.7 mg/kg (experimental enrichment, far above dietary context).
  • Cd2 + Se50 treatment (2 mg/kg cadmium (Cd) + 50 mg/kg Se NPs): 125.2 to 162.1 mg/kg (48.7 to 69.4% reduction vs. Cd2 alone).
  • Chinese national food safety standard (GB 2762-2022): cadmium maximum 0.2 mg/kg fresh weight for mushrooms (approximately 2 mg/kg dry weight).
  • CK values exceed the Chinese standard: 4.2 to 26.0 mg/kg dry weight corresponds to approximately 0.4 to 2.6 mg/kg fresh weight.

Subcellular cadmium distribution (% of total, all treatments):

  • Cell wall fraction: 82.9 to 95.8%.
  • Soluble fraction: 3.6 to 15.7%.
  • Organelle fraction: 0.6 to 3.2%.

Methods (brief)

ICP-MS (NEXION 350D, PerkinElmer) for cadmium and selenium. Freeze-dried AbM powder digested with HNO3 and HClO4. Recoveries: Cd 93 to 98%, Se 95 to 99%. Se chemical forms analyzed by LC-AFS (SA-50, Beijing Jilian). Subcellular fractionation by differential centrifugation. Non-targeted metabolomics by UHPLC-MS/MS.

Evidence fitness

Mechanistic substrate-amendment study; the CK cadmium values (background accumulation from naturally contaminated Chinese cultivation substrate) are the principal contribution to the contamination profile for AbM. Cadmium concentrations in the CK fruiting bodies range from approximately 0.4 to 2.6 mg/kg fresh weight, well above the Chinese ML of 0.2 mg/kg fresh weight, indicating that AbM grown on typical Chinese compost substrates is a high-cadmium cultivated mushroom. Limitation: experimental substrate enrichment treatments are not dietary relevant; CK values are the relevant occurrence data. Strain and substrate are specific to Chinese production conditions.

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