Qingqing Zhang

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.

Circulating tumor cells (CTCs), crucial biomarkers for monitoring cancer metastasis and prognosis, present significant challenges for detection technologies due to their extremely low abundance in peripheral blood. This study introduces a low-field nuclear magnetic resonance (LF-NMR) biosensor leveraging the synergistic effect of biorthogonal chemistry and click chemistry for CTC detection by a sol-gel phase-transition strategy. Initially, CTCs were targeted and enriched using mucin 1-specific aptamers. Subsequently, Cys-GO@CuO nanoprobes were assembled quantitatively on captured CTCs through target-triggered bioorthogonal chemistry: sialic acid molecules on the cell membrane were oxidized by NaIO₄ to generate aldehyde groups, enabling their covalent coupling with thiol/amino groups of nanoprobes via thiazolidine bond formation. Then, acidolysis reduction of CuO released Cu⁺ ions, catalyzing azide-alkyne cycloaddition click reactions to drive sol-gel phase transitions. Quantitative CTC analysis was achieved by monitoring LF-NMR-derived transverse relaxation time (T₂) signal changes. Under optimal conditions, the detection limit for MCF-7 cells is as low as 5 cells/mL, with satisfactory precision and accuracy for real samples. This integrated platform offers a sensitive, accurate, stable, and operationally simple method for CTC detection, showcasing promising applications for liquid biopsy and precision medicine.

The isolation and detection of circulating tumor cell (CTC) is of great significance for clinical cancer diagnosis and personalized therapy. Herein, a novel pangolin-type fluorescence imaging strategy is proposed to recognize, isolate and image CTC in whole blood. By combining ferroferric oxide (Fe₃O₄) nanoparticles modified with aptamer (Apt), poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(1,4-benzo-{2,1',3}-thiadiazole)] (PFBT) and poly(styrene-co-maleic anhydride) (PSMA) formed in situ a large number of polymer dots (Pdots) on the surface of graphene oxide (GO), yielding a μm-sized 2D fluorescent probe Pdots@GO@Fe₃O₄-Apt. This probe could quickly recognize CTC and overlap each other on its surface, forming a "pangolin" structure where the CTCs were wrapped in a layer of "armor". After rapidly separated from the sample by magnetic force, the morphology of the whole CTC could be observed by excited Pdots. The recognition, isolation and imaging of CTC were integrated in the probe, resulting in a high consistency between capture and imaging and ensuring high detection confidence. The feasibility of the pangolin-type fluorescence imaging strategy to detect CTC in actual samples was verified, demonstrating potential for clinical application.

A target-triggered, enzymatic cascade-amplified low-field nuclear magnetic resonance (LF-NMR) sensor was developed for the detection of the circulating tumor cell (CTC) A549. A multifunctional two-dimensional bionanomaterial GDA@GOX&DNA1 was designed as the initiator, with Fe₃O₄@DNA2/Apt as the recognition unit and CaO₂@MnO₂ as the signal unit. When A549 was present, the aptamer (Apt) detached from the recognition unit, allowing the formation of GDA@GOX&DNA1-DNA2@Fe₃O₄ and triggering the following reactions: (1) glucose oxidase (GOX) catalyzed the reaction between the substrate glucose and oxygen (O₂) to produce gluconic acid and hydrogen peroxide (H₂O₂); (2) the generated acid and H₂O₂ reacted with MnO₂, producing signal probes Mn²⁺ and O₂; and (3) CaO₂ reacted with the acid, generating H₂O₂. These cyclic reactions brought the generation of massive Mn²⁺ and a decrease of the transverse relaxation time (T₂), resulting in a target-triggered, enzymatic cascade-amplified LF-NMR biosensing of CTCs. Under the optimal experimental conditions, the linear range and limit of detection (LOD) were 10-1.0 × 10⁶ and 6 cells/mL, respectively. The feasibility and reliability in practical applications were verified by using spiked whole blood samples containing A549 cells. This study represents the first successful demonstration of an LF-NMR biosensor for the detection of intact CTCs, providing a new tool for clinical testing and diagnosis.