Cytotoxicity assay
Cell viability was measured by a CCK-8 assay in 96-well plates. FVIOs at various concentrations (0-1000 μg/mL) were added into each well that seeded with HEK293T cells 24 hours prior. Then, the FVIOs were removed from the culture media. Then, 100 μL of CCK-8 (mg/mL in DMEM) was added into each well and incubated for 2 hours. The absorbance of the supernatant was assayed using a 96-well plate reader at 450 nm.