A polyaniline-based ECL cytosensor for sensitive detection of circulating tumor cells

Circulating tumor cells (CTCs) are pivotal biomarkers for early cancer diagnosis and prognosis evaluation. However, their extremely low abundance and high heterogeneity in blood pose significant challenges for developing specific CTC detection platforms. Herein, a high-performance electrochemiluminescence (ECL) cytosensor was developed based on an electrodeposited polyaniline (PANI) substrate with reticular fibrous architecture. This platform integrated dual-aptamer recognition targeting CTC surface proteins with hybridization chain reaction (HCR)-mediated signal amplification. The PANI network morphology not only accelerated electron transfer kinetics but also effectively promoted the generation and adhesion of more filamentous pseudopodia, substantially enhancing cell capture efficiency. The cytosensor utilized a signal probe (SA@Ru-M1) to recognize the MUC1 protein on the cell surface and to react with tripropylamine (TPrA) in solution that causes ECL signal changes for the quantitative detection of model CTCs (MCF-7 cells). It demonstrated favorable analytical performance with a wide linear range from 10² to 10⁶ cells per mL and a detection limit of 31 cells per mL (S/N = 3), equivalent to a single-cell detection level on the cytosensor considering the sample volume and capture efficiency. This ECL cytosensor shows reliable detection performance in complex matrices, displaying great application prospects in biological detection and clinical diagnosis.