Hierarchical magnetic nano-orb-assisted fluorescence recovery aptasensor for sensitive detection of aflatoxin M₁ in...

Aflatoxin M₁ (AFM₁) contamination in milk and dairy products poses a significant food safety concern, highlighting the need for sensitive and reliable analytical methods. Herein, we developed a fluorescence recovery aptasensor that integrates hierarchical magnetic nano-orbs (HMO) as magnetic capture probes with aptamer-functionalized green-fluorescent silica nanoparticles (Apt-GFSN) as fluorescent signaling probes for AFM₁ detection. Three magnetic capture platforms, including magnetic beads (MBs), single-core magnetic nanoparticles (SMN), and HMO, were comparatively evaluated to elucidate the influence of magnetic architecture on probe capture and separation performance. HMO exhibited rapid magnetic separation and enhanced fluorescent probe capture, thereby reducing background fluorescence and improving signal recovery. The sensing mechanism relies on AFM₁-induced disruption of the aptamer-complementary DNA duplex, which releases Apt-GFSN from the magnetic assemblies and generates a concentration-dependent fluorescence response. Under optimized conditions, current aptasensor achieved a detection limit of 30 pg/mL and showed high selectivity toward AFM₁ over structurally related mycotoxins, veterinary antibiotics, and common milk components. The sensor also exhibited good reproducibility and stability, while analysis of commercial milk samples afforded recoveries of 93.81-100.42%, consistent with ELISA and HPLC results. This study demonstrates that rational engineering of magnetic capture architectures can improve fluorescence recovery aptasensing and provides a practical strategy for sensitive AFM₁ determination in milk.