Phosphatidylserine translocation in MOLT-4 cells treated with Pd@W.tea NPs was determined by the Annexin-V-FITC/propidium iodide (PI) apoptosis detection kit (Sigma-Aldrich Co.).21 (link) In brief, cells treated with 0.006 μM Pd@W. tea NPs for 12, 24, or 48 h were harvested, washed with PBS twice, resuspended in binding buffer, and incubated with Annexin V-FITC and propidium iodide solutions at room temperature in the dark for 30 min. Apoptosis was determined by flow cytometry using FACS Calibur (BD Biosciences, San Jose, CA, USA) with 15,000 ungated cells.