A target-triggered cascade colorimetric biosensor based on PCN-222(Fe)/GOx nanozyme for rapid detection of antibiotic...

The widespread dissemination of antibiotic resistance genes (ARGs) in the environment poses a serious threat to public health. Herein, we develop a cascade colorimetric biosensor based on a PCN-222(Fe) metal-organic framework nanozyme and glucose oxidase (GOx) for the sensitive detection of ARGs. Encapsulation of GOx within the mesoporous structure of PCN-222(Fe) endows the composite with both peroxidase-mimicking and glucose oxidase-like activities, enabling efficient dual-enzyme cascade catalysis. After functionalization with oligonucleotides, the presence of target ARGs triggers probe assembly via DNA hybridization, forming a bridged cascade system that minimizes intermediate diffusion loss and amplifies the detection signal. The biosensor exhibits a linear response to the target gene in the range of 0-100 nM (R² = 0.991) with a detection limit of 4.18 nM, and demonstrates excellent specificity in discriminating base-mismatched sequences. Recovery rates in spiked sludge samples range from 91.1% to 118.9% with relative standard deviations below 4.0%. This amplification-free platform combines visual readout, operational simplicity, and high sensitivity, offering an effective solution for point-of-care environmental monitoring of ARGs.