This study reports the development of a microfluidic beads-based nucleic acid sensor for sensitive detection of circulating tumor cells in the blood using multienzyme-nanoparticle amplification and quantum dots labels.In this method,the microbeads functionalized with the capture probes and modified electron rich proteins were fabricated within a microfluidic channel as sensing platform,and the gold nanoparticles (AuNPs) functionalized with the horseradish peroxidase (HRP) and DNA probes were used as label.Two signal amplification approaches are integrated to enhance sensitivity for detection of circulating tumor cells: first,the large surface area of Au nanoparticle carrier allows several binding events of HRP on each nanosphere.Secondly,enhanced mass transport capability inherent from microfluidics leads to higher capture efficiency of targets because continuous flow within micro-channel delivers fresh analyte solution to the reaction site which maintains a high concentration gradient differential to enhance mass transport.Based on the dual signal amplification strategy,the developed microfluidic bead-based nucleic acid sensor could discriminate as low as 5 fM (signal-to-noise (S/N) > 3) of synthesized carcinoembryonic antigen (CEA) gene fragments and showed a 1000-fold increase in detection limit compared to the off-chip test.In addition,using spiked colorectal cancer cell lines (HT29) in blood as a model system,this on-chip format could detect reverse transcription-polymerase chain reaction (RT-PCR) products of tumor cell as low as 1 tumor cell (e.g.CEA expressing cell) in 1 mL blood sample containing millions of nucleated blood cells.This microfluidic beads-based nucleic acid sensor is a promising platform for disease-related nucleic acid molecules at the lowest level at their earliest incidence.