document: In vitro cell studies. The cultured U87MG cells (5,000 cells/well) were treated with Qβ VLPs with final concentrations of 0.5, 1.0, 2.0, and 4.0 μM followed by incubation for 24 h to verify the cytotoxicity of Qβ VLPs. The culture medium was removed, and the cells were incubated in 120 μL of XTT solution for 2 h. After that, 100 μL of XTT solution from each well was transferred to another 96-well counting plate. The survival of U87MG cells was evaluated by OD at 490 nm using a SpectraMax M2