J Colloid Interface Sci. 2026 Apr 4;717:140416. doi: 10.1016/j.jcis.2026.140416. Online ahead of print.

ABSTRACT

Metal-organic framework (MOF) nanozymes serve as promising biomimetic interfaces for biocatalysis, yet bulk three-dimensional (3D)-MOFs still suffer from insufficient active site accessibility and unclear catalytic mechanisms. Herein, this study reported the rational design of an ultrathin two-dimensional (2D) single-atom MOF nanozyme, denoted as Zn-TCPP(Fe), for efficient peroxidase (POD)-like catalysis and dual-mode H₂O₂ biosensing. Synthesized via a surfactant-assisted strategy, Zn-TCPP(Fe) nanozyme (with a thickness of ∼2.25 nm) featured atomically dispersed FeN₄ active sites that structurally biomimicked the natural horseradish peroxidase (HRP). Consequently, Zn-TCPP(Fe) nanozyme exhibited a remarkable enzymatic specific activity of 80.32 U mg^-1, approximately 16-fold higher than traditional iron-based Fe₃O₄ nanozymes. The superior catalytic activity of Zn-TCPP(Fe) nanozyme originated from a spin-forbidden reaction pathway, which was efficiently facilitated by the spin crossover via a two-state reactivity (TSR) mechanism. Based on this, a complementary dual-mode biosensing platform of Zn-TCPP(Fe) nanozyme was established by integrating colorimetry and chemiluminescence (CL) assays. The colorimetric method offered a broad linear range (1-200 μM), while the CL approach achieved an ultra-sensitive limit of detection (LOD of 3.87 nM), together forming a versatile H₂O₂ biosensing platform that combined both routine practical analysis and trace-level quantification. The dual-mode biosensing platform was successfully applied to monitor endogenous H₂O₂ levels in various tumor cells, accurately differentiating them from normal cells. Overall, this work highlighted the synergistic engineering of 2D morphology and single-atom MOF nanozymes, providing fundamental catalytic mechanistic insights into spin-state-dependent nanozyme biocatalysis.

PMID:41946286 | DOI:10.1016/j.jcis.2026.140416