Their size is appropriate to extravasate the leaky pore of tumor vasculature via EPR effect.25–27 Expectedly, Au-si-CYP2S1 could effectively suppress CYP2S1 expression in both BRAFV600E-mutated and BRAF wild-type thyroid cancer cells compared to the control (Supplementary Fig. 8c). This evidence concerns the gene BRAF and thyroid cancer.