Multi-nanozyme cascade system for boosting colorimetric sensing by selective etching bimetallic MOFs

Background

Rational engineering of multienzyme system architecture is essential for achieving high-performance multi-enzyme cascade catalysis in sensing applications. In this context, the initiation step of the cascade reaction pathway plays a pivotal role in enhancing catalytic efficiency. CoFe Prussian blue analogue (CoFePBA), a dual-metal organic framework, is an ideal template for multi-enzyme design, leveraging its diverse dual-metal ion functionalities and synergistic effects. Defect engineering approaches enable the fine-tuning of catalytic properties, optimizing electron transfer and promoting reaction intermediates. Therefore, the rational design of the multienzyme system structure is critical for efficient cascade catalysis.

Results

In this study, we utilized deep eutectic solvents (DES) to selectively induce Co defects in CoFePBA (CoFePBA-DES) under mild conditions, providing more active sites and enhancing the Co²⁺/Co³⁺ ratio, significantly boosting the initial step of the cascade reaction. This then triggers the three-enzyme cascade reaction system—oxidase (OXD), superoxide dismutase (SOD), and peroxidase (POD)—which facilitates the conversion of products from O₂ to O₂^•- to endogenous H₂O₂, achieving a two-fold increase in its yield and subsequently to OH^• in a sequential reaction, demonstrating excellent multi-enzyme cascade catalytic activity. Utilizing the inhibitory effect of glutathione (GSH) on multi-enzyme cascade catalytic activity, we designed a highly efficient and rapid colorimetric sensor for the sensitive detection of GSH, with a detection range of 0.5–160 μM and a detection limit of 0.15 μM.

Significance

Compared to traditional etching techniques, DES-based methods offer superior selectivity, lower toxicity, and better structural preservation of the MOF framework, making them a promising tool for controlled defect engineering. By selectively creating defects, the initial steps of the cascade reaction are activated, resulting in a significant enhancement of catalytic activity. This approach provides a viable pathway for the preparation of high-performance dual-metal catalysts for cascade reaction catalysts and sensing applications.