Accordion-shaped MXene/PANI-Pd loaded with dual aptamer rolling circle-amplified 3D DNA networks for enhanced sensitivity in circulating tumor cell detection

The high mortality rate associated with metastasis poses a major threat to human health. Circulating tumor cells (CTCs), being the dominant factor leading to tumor metastasis, are an advantageous target of liquid biopsy and an important biomarker for prognosis and cancer monitoring. Here, we report a sensing strategy based on accordion-like multilayered Ti₃C₂ MXene-polyaniline-palladium nanoparticles (MXene/PANI-Pd) and dual aptamer rolling circle-amplified (RCA) 3D DNA networks to trap CTCs and generate electrochemical signals. The abundance of metal active sites on Ti₃C₂ MXene, the high electron transfer efficiency of PANI, and the favorable catalytic properties of Pd NPs markedly improved the electrochemical performance of the composite nanomaterials. Biorecognition aptamers (sgc8c and SYL3C) were combined with RCA to generate 3D DNA networks whose structures enhanced their affinity to epithelial adhesion molecules in CTCs (MCF-7 cells). Under optimized conditions, the constructed sensor showed a satisfactory detection performance for MCF-7 cells in the range of 10 to 1 × 10⁶ cells/mL, with a detection limit of 8 cells/mL. In addition, the responsive CRISPR/Cas12a system activated Cas12a nuclease, which cleaved dsDNA in a specific base-pairing manner to initiate deoxyribonuclease activity, releasing captured cells without causing damage or destruction. This strategy facilitates non-destructive recycling and regeneration, providing new opportunities for cell biology research. Collectively, this RCA-based DNA network capture method can be expanded to create a versatile platform for detecting various CTCs at low concentrations and enabling non-destructive recycling using CRISPR/Cas12a.