Circulating　tumor　cells　(CTCs)　have　been　detected　by　us　and　others　in　cancer　patient　blood.　However,　little　is　known　about　how　to　specifically　capture　and　deactivate　CTCs　in　vivo,　which　may　lead　to　successful　metastasis　prevention　in　asymptomatic　cancer　survivors　after　surgery.　We　hypothesize　that　the　dual　antibody　conjugates　may　have　the　advantage　of　capturing　CTCs　specifically　over　their　single　antibody　counterparts.　Here　we　show　that　the　surface-functionalized　dendrimers　can　be　sequentially　coated　with　two　antibodies　directed　to　surface　biomarkers　(EpCAM　and　Slex)　of　human　colorectal　CTCs.　The　dual　antibody-coated　dendrimers　exhibit　a　significantly　enhanced　specificity　in　capturing　CTCs　in　the　presence　of　interfering　blood　cells,　and　in　both　eight-patient　bloods　and　nude　mice　administered　with　the　labeled　CTCs　in　comparison　to　their　single　antibody-coated　counterparts.　The　dual　antibody-coated　conjugates　down-regulate　the　captured　CTCs.　This　study　provides　the　first　conceptual　evidence　that　two　antibodies　can　be　biocompatibly　conjugated　to　a　nanomaterial　to　capture　and　down-regulate　CTCs　in　vivo　with　the　enhanced　specificity.　(C)　2015　Elsevier　B.V.　All　rights　reserved.