A fluorescent aptasensor based on the synergy of Au NPs/PDDA/LEG nanocomposite and CDs for aflatoxin B1 detection

Aflatoxin B1 (AFB₁), a potent carcinogen produced by Aspergillus fungi, contaminates foods such as corn and peanuts and thereby introduces a serious food safety risk, as it is known to cause liver damage and cancer. Therefore, developing sensitive and rapid detection methods is crucial for protecting public health. This work presented a highly sensitive aptasensor for AFB₁ detection, utilizing a fluorescence quenching and recovery strategy based on a gold nanoparticles/poly (diallyldimethylammonium chloride)/liquid-phase exfoliation of graphene (Au NPs/PDDA/LEG) nanocomposite. The composite sensing platform was constructed by employing PDDA to enhance the dispersion of LEG and prevent the aggregation of Au NPs. Aptamers were immobilized onto the Au NP surface via Au-S bonds. Concurrently, carbon dots (CDs) were conjugated to complementary DNA (cDNA) to form cDNA/CDs. In the absence of AFB₁, hybridization between the aptamer and cDNA brought CDs into close proximity with Au NPs, resulting in the quenching of CDs fluorescence due to the proximity to Au NPs. Upon the introduction of AFB₁, its specific binding to the aptamer competitively displaced cDNA/CDs. This displacement separated CDs from the Au NPs, leading to the recovery of fluorescence intensity. Demonstrating excellent analytical performance, the sensor offered not only a wide linear detection range (1.0 × 10^-2-1.0 × 10³ ng mL^-1), but also a remarkably low limit of detection (LOD) at 1.05 pg mL^-1. Testing with corn and peanut samples yielded high recovery rates of 97.63% to 109.65%, confirming the method's reliability, accuracy, and significant potential for practical food safety monitoring of AFB₁.