Fast-Scan Voltammetry-Driven Nanoprobes for the Intracellular PTP1B Activity Assay and Invasiveness Evaluation of Single Tumor Cells

In this study, a fast-scan voltammetry (FSV)-driven nanoelectrochemical biosensing system was constructed for in situ detection of intracellular protein tyrosine phosphatase 1B (PTP1B) activity and evaluation of single tumor cell invasiveness. In this system, a platinum nanoelectrode (PtNE) was used as the substrate, on which a PTP1B-specific phosphopeptide (P-peptide) was immobilized via Pt–S bonds. Subsequently, the signal probes zirconium-based metal–organic frameworks@gold nanoparticles@ferrocene (UiO-66@Au@Fc) were assembled onto the electrode surface through Zr–O–P coordination bonds to form the sensing interface. Upon catalytic dephosphorylation of the P-peptide by PTP1B, the signal probe UiO-66@Au@Fc detached from the electrode surface, leading to a decrease in current. Benefiting from the high scan rate of FSV, the sensor enabled signal acquisition within milliseconds, effectively suppressing background currents and allowing monitoring of intracellular enzymatic reactions at the single-cell level. The sensor exhibited a detection limit as low as 1.0 × 10 –14 mol/L for PTP1B, along with excellent specificity and reproducibility. Using this platform, the dynamic variation of PTP1B activity during the invasion process was successfully captured in a transforming growth factor-β1 (TGF-β1)-induced invasion model of MCF-7 human breast cancer cells, and the responses to anticancer drugs cisplatin (CDDP) and paclitaxel (PTX) were further evaluated. This work provides a new analytical strategy for the dynamic analysis of tumor invasion-related enzyme activity and drug sensitivity evaluation at the single-cell level.