Engineering Dimensional Configuration of Single-Atom S-Cu-S Sites as Reversible Electron Station for Enhanced Peroxidase-Mimicking.

Boosting catalytic activity of single-atom nanozymes (SAzymes) to substitute natural metalloenzymes remains challenging due to the lack of enzyme-like secondary building blocks and proper 3D conformation. Herein, a natural amino acid L-cysteine (L-Cys)-triggered auto-assembly process engineers the spatial positioning of 3D-biomimetic S-Cu-S single-atom catalytic sites and adjacent L-Cys on sheet-like MoS₂ nanozyme, achieving activated MoCC SAzymes. MoCC achieves a maximum Cu single-atom loading of 10.11% by suppressing aggregation through L-Cys coordination. Particularly, MoCC can properly bind and react with the H₂O₂ substrate, mimicking 3D catalytic pockets of natural enzymes. The maximum reaction velocity (4.56×10^-7 M s^-1), affinity (Michaelis constant, 0.65 mM), and specific activity (SA) (355.59 U mg^-1) catalyzed by peroxidase (POD)-mimicking MoCC are 16.3-, 17.9-, and 1.2-fold higher than natural horseradish peroxidase (HRP). Density functional theory computations reveal that the S-Cu-S single-atom catalytic sites stabilized by L-Cys bonding function as a reversible electron flow workstation, triggering storage and transfer with MoS₂, facilitating swift electron exchange with H₂O₂, reducing energy barrier for hydroxyl radicals generation. The optimized 3D S-Cu-S single-atom featuring L-Cys building of MoCC exhibits cascaded catalase-like activity and sono-piezocatalysis effect, non-invasively amplifying the generation of oxygen and singlet oxygen. Consequently, multiple free radicals can selectively eliminate dental bacteria and biofilms.