A surface-enhanced Raman scattering aptasensor for output-signal detection of aflatoxin B1 based on peroxidase-like Cu2O@Au hybrid nanozyme

Abstract

Aflatoxin B1 (AFB1) as toxic secondary metabolite significantly threatens human health. Hence, we designed a reliable “target control signal output” surface-enhanced Raman scattering (SERS) aptasensor based on catalytic reaction and signal amplification induced by bifunctional semiconductor-bimetallic plasmonic assemblies to monitor AFB1 contamination. SH-modified AFB1 aptamers were coupled to hollow Au–Ag NPs with enhanced SERS features, enabling rapid identification of AFB1. As artificial nanoenzymes, self-assembled Cu2O@Au NCs with peroxidase-like activity produced synergistic catalytic enhancement effects. Complementary chain-modified Cu2O@Au NCs promoted the construction of bifunctional composites. Besides, the preferred binding of the aptamer to AFB1 triggered the dissociation of Au–Ag NPs, causing the reduced SERS effect. Then, in the 3,3′,5,5′-tetramethylbenzidine (TMB) reaction mediated by nanoenzymes, oxidation products (ox TMB) with intrinsic Raman signals appeared, which were ideal quantitative signal. Compared with the labeled detection, the novel post-output mode of SERS signal reduced the signal fluctuation in the sensor construction and improved the accuracy of the results. Thus, the aptasensor exhibited a strong negative linear correlation (R2 = 0.991) in the AFB1 concentration ranging from 0.001 ng/mL to 100 ng/mL, and the detection limit (LOD) was 0.7 pg/mL, indicating that the integration of SERS and enzymatic reactions has potential application prospects in test technology.