An innovative indirect competitive immunosorbent approach for precise detetion aflatoxin B ₁ based on high-affinity IgG coupled CuO-anchored Fe ₃O ₄ nanozymes

Aflatoxin B₁ (AFB₁) is a carcinogenic toxin naturally produced in most food crops that severely threaten human health, and effective methods are urgent to improve the detection accuracy. Herein an indirect competitive immunosorbent approach was elaborately developed based on high-affinity immunoglobulin G (IgG) coupled CuO-anchored Fe₃O₄ nanozymes for precise and ultrasensitive detection of AFB₁ in food crops including peanut, corn and wheat. The high-affinity nanozymes were fabricated by the assembly of inner core Fe₃O₄nanoparticles (Fe₃O₄NPs) and mesoporous silica capping layer, CuO further situated within large aperture of the coating layer via in-situ growth, and then conjugated with ligand rabbit anti-mouse IgG, which can specifically bind with AFB₁. The results showed the hybrid high-affinity nanozymes displayed enhanced peroxidase (POD)-mimic activities and catalytic performances, achieving a linear range of 0.06-61.93 ng/mL and a detection limit of 0.0037 ng/mL, 30 times better than that of the conventional ELISA method. The constructed nanozymes were successfully applied to the detection of AFB₁ in food products with an average spiked recovery of 96.53% and relative standard deviations (RSDs) less than 2.8%. Therefore, the accurate hybrid nanozymes may serve for AFB₁detection in various foods in future.