A Single Aptamer-Dependent Sandwich-Type Biosensor for the Colorimetric Detection of Cancer Cells via Direct Coordinately Binding of Bare Bimetallic Metal–Organic Framework-Based Nanozymes

A typical colorimetric sandwich-type sensor relies on dual antibodies/aptamers to specifically visualize the targets. The requirement of dual antibodies/aptamers and low signal intensity inevitably increases the design difficulty and compromises the sensing sensitivity. In this work, a novel sandwich-type aptasensor was developed using single aptamer-functionalized magnetic nanoparticles as a specific recognition unit to target cancer cells and a bimetallic metal–organic frameworks (MOFs)-based nanozymes as a colorimetric signal amplification unit. The well-defined crystalline structure of UIO-66 MOFs enabled the introduction of Fe/Zr bimetal nodes, which possessed integrated properties of the peroxidase-like nanozyme activity and direct coordinately binding to the cell surface. Such a novel construction strategy of sandwich-type aptasensors achieved simple, sensitive, and specific detection of the target cancer cells, which will inspire the development of biosensors.