A Cascaded Chip for the High-Purity Capture and Distinguishing Detection of Phenotypic Circulating Tumor Cells in Colon Cancer

The low abundance, complex phenotypes, and need for sophisticated blood preprocessing pose substantial obstacles to the clinical implementation of circulating tumor cells (CTCs). Herein, we constructed a cascaded PMMA chip-based platform for the separation of CTCs from other cells within blood samples, as well as distinguishing the detection of epithelial and mesenchymal CTCs. The primary physical separation chip (PS-Chip) focused and sorted CTCs from whole blood via Dean flow fractionation (DFF) according to size differences between CTCs and other blood cells, being capable of eliminating approximately 93.7% of red blood cells (RBCs) and 68.4% of white blood cells (WBCs) from whole blood while maintaining a CTC recovery rate of around 90%. Subsequently, to further purify the isolated CTCs in the upstream, a partitioned immunoaffinity capture and detection chip (PICD-Chip) featuring with two independent chambers (Zone 1, Zone 2) was designed, each of which was premodified with Gel-GO/E/V-Apt complexes that specifically recognize CTCs with distinct phenotypes, enabling further separation of residual blood cells from the upstream isolation. Upon the subsequent introduction of two detection probes, namely EpCAM and vimentin aptamer-modified mesoporous Pt nanoparticles (mPtNPs/E/V-Apt), into Zone 1 and Zone 2, respectively, heterogeneous CTCs ranging from 5 to 200/mL captured within two chambers were distinguished and quantified utilizing the exceptional peroxidase activity of mPtNPs. The integrated approach of efficient enrichment and differentiation detection of phenotypic CTCs under the requirement of high purity has enabled the successful application of the cascaded chip in the diagnosis of colon cancer patients at different stages.