2024 Volume 34 Pages 9-20
Silver-containing nanoparticles (Ag-NPs) are now used in a wide range of consumer products for their antibacterial properties. Human exposure to Ag-NPs can occur not only through contact with these products but also through foods that have become contaminated with Ag-NPs released from these products into the environment. However, the status of NPs in foods remains unknown due to the lack of an analytical method for the examination of NPs contained in solid samples such as foods. Recent evidence suggests that Ag-NPs released into the environment may accumulate in filter feeders such as oysters. Here, we developed a method for measuring the concentrations of Ag-NPs in oysters using single-particle inductively coupled mass spectrometry (spICP-MS). Ag-NPs were extracted from oysters using one of four extraction procedures (ultrasonic crushing, alkali-treated hydrolysis, solubilization with surfactant, or enzymatic digestion), and recoveries of spiked Ag-NP (diameter, 60 nm) in terms of particle size, particle number concentration, and particle mass concentration were evaluated. Among the four extraction procedures, enzymatic degradation afforded the highest recoveries for particle number concentration (85±13%) and particle mass concentration (93±14%) and had the smallest effect on particle size (110±3%). Using our developed spICP-MS approach with enzymatic degradation, we examined 24 samples of rock and Pacific oysters purchased on the Japanese market between 2019 and 2020 and found that they contained Ag-NPs at 6.3×105 to 7.7×108 particles/g. The particle mass concentrations ranged from 0.13 to 98 ng/g, and an average of 1.2% of the total Ag was present as nanoparticles. The present data also suggest a difference in the size of the Ag-NPs accumulated in rock oysters (28±2 nm) and Pacific oysters (25±4 nm); further studies are needed to examine this finding in more detail.
