Circulating tumor cells(CTCs),as a kind of liquid “biopsy”,represent a potential alternative to invasive detection,characterization,and monitoring of carcinoma1.Many previous studies have shown that the number of CTCs has significance relationship with the stage of cancer2,3.However,CTCs enrichment and detection has long been facing a huge challenge due to the fact that CTCs exist in bloodstream which contains a large number of hematological cells4.Herein,we have designed a magnetically controlled microfluidic device combined with magnetic nanospheres fabricated by layer-by-layer assembly method for efficient capture and sensitive detection of CTCs.Firstly,with the help of permanent magnet,immunomagnetic nanospheres(IMNs)modified with anti-epithelial-cell-adhesion-molecule(EpCAM)antibody were loaded in the microfluidic device uniformly.Then sample containing CTCs was introduced into the device and CTCs were specifically captured by IMNs through their targeted recognition to the receptors on CTCs.Finally,immumocytochemistry(ICC)identification was carried out directly in the device for CTC identification and enumeration.The structure of device and the flow rate were investigated and optimized to achieve the highest capture efficiency,and under the optimal experimental condition the device was able to capture tumor cells with efficiency of about 93%.This device was also applied to the capture of some other kinds of epithelial cells and the capture efficiency kept high,showing its general applicability.Furthermore,we also successfully used this device to directly capture rare tumor cells in complex matrixes with high efficiency and good reproducibility,which suggested this device would be a promising tool for CTC enrichment and detection.Besides,most of captured cells were kept viable,and this will benefit for subsequent molecular and cellular studies.