Hierarchical MOFs with spatially ordered cascade enzymes for sensitive nitrite immunosensing.

Area of Science:

• Biotechnology and Nanomaterials Science
• Enzyme Engineering and Immobilization
• Biosensor Development

Background:

• Immobilized enzyme efficiency is crucial for sensitive immunosensors, but random enzyme distribution limits cascade reactions.
• Controlling enzyme spatial arrangement is key to improving intermediate transfer and overall catalytic efficiency.

Purpose of the Study:

• To create a spatially ordered multilayer metal-organic framework (MOF) for enhanced cascade enzyme activity.
• To improve enzyme encapsulation and mass transfer within the MOF structure.
• To demonstrate the application of this composite as a signal amplifier in a highly sensitive immunosensor.

Main Methods:

• Constructed a multilayer MOF using spatially ordered hierarchical assembly for enzyme compartmentalization.
• Optimized enzyme encapsulation using polyvinylpyrrolidone (PVP) and histidine (His) for microenvironment regulation.
• Utilized Ni-triggered etching to enlarge MOF pores, reducing mass transfer resistance.

Main Results:

• Achieved ordered spatial compartmentalization of glucose oxidase (GOx) and horseradish peroxidase (HRP).
• High GOx encapsulation efficiency of 74.43% was obtained.
• MOF pore size increased from 2.21 nm to 5.68 nm, doubling cascade enzyme catalytic activity.
• The composite demonstrated ultrahigh sensitivity for nitrite detection with a limit of detection of 0.05 μg/mL, a 1000-fold improvement over conventional methods.

Conclusions:

• The developed MOF strategy enables efficient immobilization and activity enhancement of cascade enzymes.
• Ordered enzyme arrangement within MOFs significantly improves catalytic efficiency and immunosensor performance.
• This approach offers a valuable method for constructing highly sensitive immunosensors using controllable nanostructures.