Pore-confined synthesis of ultra-small Pt nanozymes on gold nanobipyramids for electrochemical detection of cancer cell-derived H2O2.

Accurate quantification of H2O2 released by tumor cells is important for characterizing cancer-associated oxidative stress, yet conventional biosensors often face an intrinsic trade-off between catalytic activity and structural stability. Herein, we present a rational strategy for real-time electrochemical monitoring of cancer-associated oxidative stress species through the in-situ fabrication of ultrasmall Pt nanozymes confined within the mesoporous silica shell of gold bipyramids (AuPt@SiO2). In this architecture, the Au core provides conductive nucleation and anchoring sites, the mesoporous SiO2 shell regulates Pt growth and affords structural stabilization and molecular-sieving protection, and Pt serves as the catalytic center for H2O2 reduction. The resulting AuPt@SiO2 nanozyme exhibited pronounced peroxidase-like activity with a favorable Michaelis-Menten constant (Km) of 6.08 mM toward H2O2. After integration into a Nafion-based sensing interface, the enzyme-free sensor provided complementary linear ranges of 0.25-60 mM by cyclic voltammetry and 1-2100 μM by amperometry with a detection limit at 0.3 μM of H2O2. The electrochemical sensor based on AuPt@SiO2 also demonstrated excellent repeatability and exceptional stability, retaining over 85% of its initial response after 30 days. Importantly, this platform enabled label-free monitoring of phorbol 12-myristate 13-acetate (PMA)-triggered H2O2 efflux from MGC-803 gastric cancer cells and differentiated their oxidative-stress phenotype from that of normal gastric epithelial cells. The apparent H2O2-equivalent response normalized to cell number was approximately 1.72 × 10-13 M per cell. This work highlights the potential of confined nanozymes for high-performance H2O2 sensing and precise pathological profiling at the single-cell level.