The main reason for most cancer deaths is tumor metastasis.Circulating tumor cells (CTCs) are thought to be responsible for metastasis,so the capturing and restraining of CTCs may serve as an efficient toolto prevent metastasis.In this work,we aimed to synthesize and characterize duel-aptamer-mesoporous silica nanoparticles (MSNs),and test the efficiency of aptamer-MSNs in capturing and down-regulation of CTCs.We used two kinds of aptamerswhich could respectively identify the molecular targets EpCAM and CD44 on the surfaces of CTCsto increase recognition specificity.