Circulating tumor cells (CTCs) are a kind of tumor cells that can escape from the tumor mass to blood circulation system and further to different tissues of the body at the early stage of malignant progress1.To know why CTCs can escape from tumor mass and the relationship between CTCs and tumor metastasis,it is very important to establish a method for capture and release of CTCs from blood without damage for further cell culture and in vitro analysis.Nanomaterials,especially nanomaterial-based functional nanodevices,are increasing in their popularity with researchers and manufacturers.Among them,fluorescent-magnetic nanoparticles are extensively studied and widely used for magnetic separation and fluorescent tracking of tumor cells2,but it is rarely reported that fluorescent-magnetic nanobioprobes can capture and release tumor cells reversibly.It is demonstrated that anti-EpCAM functionalized-alginate-Ca2+ layer can be formed and decomposed by EDTA addition for reversible capture and release of CTCs3.Inspired by this work,we synthesized fluorescent-magnetic nanoparticles with alignate-Ca2+ shell presenting good dispersibility and strong fluorescence (Figure 1).To functionalize fluorescent-magnetic nanoparticle,anti-EpCAM was conjugated for CTCs capture.Compared with control (Figure 2c and 2d),anti-EpCAM-functionalized fluorescent-magnetic nanoparticles can be recognized by FITC-labeled secondary antibody (Figure 2e and 2f).After EDTA treatment,anti-EpCAM can be released from the nanoparticles (Figure 2g and 2h),indicating that the alginate shell could assist anti-EpCAM attachment and detachment from the nanoparticle.In contrast to Hela cells (EpCAM negative),SK-BR-3 cells (EpCAM positive) can be effectively captured and released by as-prepared nanobioprobes.