Defect-regulated reduced graphene oxide anchored Prussian blue and platinum nanoparticles peroxidase for electrochemical detection of mesenchymal circulating tumor cells.

The precise analysis of mesenchymal circulating tumor cells (mCTCs), known for their enhanced migratory behavior in peripheral blood, is essential for cancer diagnosis and predicting metastasis. Nevertheless, the rarity and heterogeneity of mCTCs present significant challenges in both their capture and subsequent enumeration. Therefore, designing and realizing a high-performance and adaptable cytosensor platform are crucial for the accurate analyzing various mCTCs. Defect engineering is used to enhance the synthesis of a peroxidase mimic enzyme, achieving significantly higher activity than natural enzymes. This was accomplished by anchoring Prussian blue (PB) and platinum (Pt) nanoparticles onto reduced graphene oxide (rGO), forming rGO@PB/Pt. An electrochemical cytosensor was subsequently constructed based on rGO@PB/Pt linked with aptamers to capture mCTCs and degrade the trace hydrogen peroxide (HO) secreted by mCTCs. Specifically, the presence of Fe vacancies creates numerous active Fe sites, resulting in an enlarged specific surface area and a microporous structure with pore diameters of approximately 0.8 nm and 1.3 nm. These structural features enable the effective encapsulation of HO, enhancing its rate of decomposition. The cytosensor demonstrated a linear response within the range of 1 to 10 cells/mL, with a detection limit (LOD) as low as 0.1 cells/mL (S/N = 3). Moreover, the cytosensor can quantify mCTCs solely based on cell membrane epitopes, making it applicable to almost all types of CTCs by altering the capture aptamer. In addition, the analysis of mCTCs in human blood additionally validates it as a promising candidate for the precise detection of mCTCs in clinical settings.