Efficient detection of heterogeneous CTCs using folate modified magnetic beads combined with microfluidic spatial confinement signal amplification

Circulating tumor cells (CTCs) may be overlooked by detection techniques based on epithelial cell adhesion molecules (EpCAM) because of epithelial- mesenchymal transition (EMT). This work established an efficient microfluidic magnetic cell immunoassay (E- μ MCI) for CTCs via folate-modified magnetic beads (MBs@FA). Upon capture by MBs@FA, MCF-7 (EpCAM + Vimentin − ) and MDA-MB-231 (EpCAM − Vimentin + ) were labeled with horseradish peroxidase (HRP) and alkaline phosphatase (AP) via anti-EpCAM and anti-Vimentin, respectively. These labeled target cells were then concentrated in a microchannel’s tiny space. These phenotypes were recognized by fluorescent substances generated by HRP and AP, and cell quantity was determined via the growth rate of fluorescent products. MBs@FA’s efficient capture and microchannel’s signal amplification enabled ultrasensitive CTCs detection via E- μ MCI, with the detection limits of 1.8 and 2.8 cells/mL for MCF-7 and MDA-MB-231, respectively. This method also exhibited excellent selectivity and repeatability, achieving acceptable recovery and stability in actual sample determination. More remarkably, within the EMT model of CTCs, the recovery rate of E- μ MCI was observed to range from 94.3 % to 102.8 %. It was far greater than the EpCAM-based approach, indicating that E- μ MCI has the potential to address CTC detection oversights and offer technical methodologies for studying the relationship between CTCs and cancer progression.