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

In-situ pore-confined growth of ultra-small Pt nanoclusters within mesoporous SiO 2 . • Au-Pt@SiO 2 nanozyme exhibits superior peroxidase-like activity with K m of 6.077 mM. • Enzyme-free electrochemical biosensor achieves 0.3 μM LOD. • Exceptional long-term stability retaining >85% activity after 30 days of storage. • Real-time quantitative profiling of single cancer cell H 2 O 2 efflux upon PMA trigger. Accurate quantification of H 2 O 2 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@SiO 2 ). In this architecture, the Au core provides conductive nucleation and anchoring sites, the mesoporous SiO 2 shell regulates Pt growth and affords structural stabilization and molecular-sieving protection, and Pt serves as the catalytic center for H 2 O 2 reduction. The resulting AuPt@SiO 2 nanozyme exhibited pronounced peroxidase-like activity with a favorable Michaelis-Menten constant (K m ) of 6.08 mM toward H 2 O 2 . 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 H 2 O 2 . The electrochemical sensor based on AuPt@SiO 2 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 H 2 O 2 efflux from MGC-803 gastric cancer cells and differentiated their oxidative-stress phenotype from that of normal gastric epithelial cells. The apparent H 2 O 2 -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 H 2 O 2 sensing and precise pathological profiling at the single-cell level. Download: Download high-res image (405KB) Download: Download full-size image