In situ-assembled 3D DNA network scaffolds: a synergistic strategy for the capture and non-destructive detection of circulating tumor cells.

Circulating tumor cells (CTCs) serve as critical non-invasive biomarkers for cancer diagnosis; however, their low abundance in peripheral blood presents significant challenges for capture and detection. This study presents a novel sandwich-type electrochemical aptasensor, constructed by immobilizing tetrahedral DNA nanostructures (TDNs) on a Au NPs-graphene/graphdiyne substrate. An extended vertex strand of the TDN acts as a primer to initiate rolling circle amplification (RCA), leading to the in situ extension of long single-stranded DNA containing repetitive SYL3C aptamer sequences. This process generates flexible 3D DNA network scaffolds that utilize a multivalent, cooperative mechanism to capture target cells, significantly enhancing capture efficiency and binding stability over conventional monovalent probes or ex situ-assembled networks. For signal amplification, PdPtCuRu multimetallic nanoflowers functionalized with MUC1 aptamers are employed as electrochemical labels, enabling highly sensitive detection. The sensor demonstrates a wide linear response range from 7 to 1 × 10⁶ cells mL⁻¹, along with high specificity and stability. Furthermore, gentle cell release is achieved using benzonase nuclease, preserving cell viability for subsequent analysis. Additionally, this sensor also demonstrates good accuracy when testing human serum samples. This study provides a novel in situ interface engineering strategy for CTC detection, showing great potential for cancer liquid biopsy applications.