Regulating Rare-Earth Single-Atom Nanozyme for Colorimetric-SERS Dual-Modal Sensing of Intracellular Glutathione

Rare-earth single-atom nanozymes (RESAzymes) have emerged as promising catalysts due to their maximized atom utilization efficiency and tunable enzymatic activities. Herein, a colorimetric-Surface-enhanced Raman scattering (SERS) dual-modal sensing platform is constructed to introduce 4f electron configurations of single-atom ytterbium active site decorated on a nitrogen-doped porous carbon (Yb-N/C) by a facile hierarchical cascade-anchoring protocol. Specifically, this unique coordination environment can promote substrate molecule adsorption and activation energy barriers, possessing excellent peroxidase (POD)-mimicking activity and SERS enhancement performance in TMB-H₂O₂ system. In the presence of glutathione (GSH), Yb-N/C catalyst is inhibited to result in reducing oxTMB for returning its colorless state, consequently diminishing both the colorimetric readout and the SERS intensity. Interestingly, this reaction mechanism from Yb-N/C is systematically illustrated through the steady-state kinetic, electron paramagnetic resonance (EPR), and density functional theory (DFT) calculations. Notably, the limited of detection (LOD) of GSH with colorimetric and SERS dual-mode was as low as 0.30 and 0.11 µM, respectively. Our established dual-modal analysis for intracellular GSH exhibits the favorable consistent with the standard kit in HepG2, KYSE150, and MCF-7 cells, respectively. This work will offer an in-depth understanding of RESAzymes-mimicking activity of colorimetric-SERS biosensors by adjusting electronic structures in carbon-based carrier.