Filter‐Assisted ICP‐MS Tumor Liquid Biopsy Enabled by Dual‐Target‐Regulated Functional DNA Nanospheres Cascade Amplification

An ultrasensitive ICP-MS aptasensor is developed utilizing a label-free, simple filter membrane-assisted separation technique combined with nucleic acid signal amplification for the analysis of circulating tumor cells (CTCs) in lung cancer clinical samples. The approach is based on the high-affinity interaction between aptamers and PD-L1 and mucin 1, which are overexpressed on the cell surface, in conjunction with functional Y-DNA nanospheres and catalytic hairpin assembly amplifications, enabling the simultaneous detection of two proteins. Additionally, a four-armed nanostructure with significant spatial site resistance is self-assembled by introducing streptavidin with biotinylated-hairpin structures, improving the separation efficiency of the filter membrane. This structural design enables the effective isolation of biotin-T-Hg²⁺-T and biotin-C-Ag⁺-C from free Hg²⁺ and Ag⁺, facilitating highly sensitive dual-protein detection via ICP-MS. The limits of detection reached ag mL^-1 levels for proteins and single-cell levels for A549 cells. CTCs are extracted from whole blood samples of lung cancer patients within 45 min through a simple centrifugation procedure. Quantification of CTCs is performed in 37 clinical samples, demonstrating results consistent with clinical diagnoses. The assay exhibits a specificity of 100% and a sensitivity of 94.5%.