A novel visual-magnetic relaxation switch sensor based on an organic framework nanozyme for ultrasensitive norovirus detection.

BACKGROUND

Norovirus (NV), the predominant global cause of non-bacterial acute gastroenteritis, presents severe public health risks due to exceptional environmental stability, low infectious dose (<20 virions), and frequent transmission via contaminated food/water, particularly bivalve mollusks. Conventional detection methods require centralized laboratories, trained personnel, and lack the rapidity, portability, and ultra-sensitivity necessary for on-site surveillance within food supply chains. Consequently, a critical unmet need exists for an integrated detection strategy enabling timely identification and precise quantification of NV in complex food matrices.

RESULTS

Herein, we synthesized a Fe3O4@COF nanozyme composite by grafting a covalent organic framework (COF) material onto the surface of Fe3O4 nanoparticles. This composite integrates high peroxidase-like activity with magnetic responsiveness. The catalytic mechanism of the nanozyme was systematically investigated through density functional theory (DFT) calculations and experimental validation. Reaction conditions were optimized, and steady-state kinetic analysis was performed. Furthermore, by employing a monoclonal antibody as the signal probe, we designed a nanozyme-assisted magnetic relaxation switching (MRS) sensor strategy for the visual and precise detection of norovirus. This strategy achieves a low detection limit of 0.7 pg/mL and a broad linear detection range spanning 0.001 ng/mL to 100 ng/mL. Additionally, the method was successfully applied to analyze norovirus-contaminated oyster and scallop samples, yielding recovery rates of 92.82 %-110.63 %.

SIGNIFICANCE: This work pioneers the fusion of COF-based nanozymes with MRS sensing, creating the first visual, antibody-mediated NV detection platform. The novelty lies in the dual-functional material design enabling magnetic separation and amplified catalytic signal output. This approach significantly advances accuracy, offering ultrasensitive quantification for food safety and environmental monitoring. The platform's adaptability to other pathogens via probe modification broadens its transformative impact.