Agilent 8900 icp qqq ms

Glioma cells were seeded onto 12-well plates at a density of 1 × 10⁵ cells per well and incubated at 37 °C and 5% CO₂ in a humidified incubator. At approximately 90% confluency, cells were washed with warm PBS thrice, and then fresh medium or medium with nanoparticles was added after the final wash (final particle concentration of 50 µg/mL and final volume of 800 µL). After a 1 h incubation, the cells were washed with warm PBS twice to remove unbound nanoparticles. Cells were then detached with trypsin/ethylenediamine tetraacetic acid (0.05%, ThermoFisher, Cat.25300062), resuspend in 100 µL of 1% Bovine Serum Albumin (BSA)/PBS solution, and kept in the fridge or ice until analysis. The elemental analysis was performed using Agilent 8900 ICP-QQQ-MS fitted with an inert PFA sample introduction system. Si was measured in MS/MS mode using Hydrogen reaction gas on mass at m/z 28. 57 µL of the cell samples were digested in 1 M NaOH at a ratio of 1:3 (w/w) overnight at room temperature. The solutions were further diluted with MilliQ water and submitted for elemental analysis. The quantification was performed by external calibration with Si standards for inductively coupled plasma, which were prepared in 0.1 M NaOH from a 1000 mg/L Si standard (HPS standards), under identical settings.

Elemental content analyses were performed by inductively coupled plasma-mass spectrometry using an Agilent 8900 ICP-QQQ-MS (Agilent Technologies) with established protocols (Neville et al., 2021 (link); Brazel et al., 2022 (link)). For bacterial elemental analyses, samples were prepared as described previously (Maunders et al., 2022 (link)). Briefly, K. pneumoniae strains were subcultured in Zn(II)-limited or Zn(II)-supplemented media at 37°C with aeration to mid-log phase (OD_{600 =} 0.6-0.8) and harvested by centrifugation at 7,000 × g for 10 min at room temperature. The cell pellets were washed twice in phosphate buffered saline (PBS) containing 5 mM ethylenediaminetetraacetic acid, followed by two washes in PBS. Bacterial cell pellets were then desiccated overnight at 95°C, followed by digestion of organic material in 250 μL 65% (v/v) HNO₃ at 95°C for 20 min. For media analyses, samples were diluted 1:2 with 65% (v/v) HNO₃ and incubated at 95°C for 20 min. Digested media and whole cell pellet samples were then centrifuged at 18,000 × g for 25 min at room temperature and the supernatant diluted to a final concentration of 3.25% (v/v) HNO₃ in MilliQ H₂O (Neville et al., 2021 (link); Brazel et al., 2022 (link)).