Array-addressed scanning electrochemical cell microscopy for single-cell dual-cadherin profiling during epithelial-mesenchymal transition

Single-cell electrochemical analysis provides a quantitative approach for resolving cellular heterogeneity, but conventional measurements on randomly distributed cells often suffer from inefficient target searching, limited positional control, and low statistical throughput. Herein, we report an aptamer-directed, dual-metal-tagged electrochemical strategy implemented on an array-addressed scanning electrochemical cell microscopy (SECCM) platform for targeted profiling of two surface proteins on individual cells. An ordered single-cell array was constructed on a poly(vinyl alcohol)-modified indium tin oxide (PVA-ITO) substrate using microcontact-printed polydopamine patterns, enabling deterministic positioning of the SECCM probe over predefined cells. E-cadherin (E-cad) and N-cadherin (N-cad), two representative surface markers of epithelial-mesenchymal transition (EMT), were selectively labeled with aptamer-functionalized silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs), respectively, producing well-separated stripping signals for dual-marker readout. Using transforming growth factor-β1-induced EMT in A549 cells as a model system, the platform quantitatively captured the expected cadherin switch at the single-cell level, with the E-cad-associated charge decreasing from 1.49 ± 0.38 to 0.23 ± 0.14 nC and the N-cad-associated charge increasing from 0.26 ± 0.16 to 1.01 ± 0.41 nC after EMT induction. Dual-marker scatter analysis further resolved epithelial-like, mesenchymal-like, and hybrid E+/N+ phenotypes, revealing EMT-associated cellular heterogeneity that is obscured in ensemble measurements. This work establishes an array-addressed SECCM strategy for aptamer-based dual-marker electrochemical detection of E-cad and N-cad on predefined individual cells, providing a general framework for single-cell surface-protein profiling.