Cancer metastasis is the leading cause of death in cancer patients worldwide and one of the major challenges in treating cancer. Circulating tumor cells (CTCs) play a pivotal role in cancer metastasis. However, the content of CTCs in peripheral blood is minimal, so the detection of CTCs in real samples is extremely challenging. Therefore, efficient enrichment and early detection of CTCs are essential to achieve timely diagnosis of diseases. In this work, we constructed an innovative and sensitive single-nanoparticle collision electrochemistry (SNCE) biosensor for the detection of MCF-7 cells (human breast cancer cells) by immunomagnetic separation technique and liposome signal amplification strategy. Liposomes embedded with platinum nanoparticles (Pt NPs) were used as signal probes, and homemade gold ultramicroelectrodes (Au UME) were used as the working electrodes. The effective collision between Pt NPs and UME would produce distinguishable step-type current. MCF-7 cells were accurately quantified according to the relationship between cell concentration and collision frequency (the number of step-type currents generated per unit time), realizing highly sensitive and specific detection of MCF-7 cells. The SNCE biosensor has a linear range of 10 cells·mL–1 to 105 cells·mL–1 with a detection limit as low as 5 cells·mL–1. In addition, the successful detection of MCF-7 cells in complex samples showed that the SNCE biosensors have great potential for patient sample detection.
