A novel gold nanostars-based fluorescent aptasensor for aflatoxin B1 detection.

In this work, a simple and sensitive fluorescent aptasensor for aflatoxin B1 (AFB) detection was proposed using gold nanostars (AuNSs) as a novel fluorescence quenching material. Carboxyfluorescein-labeled complementary DNA with hairpin structure (FAM-labeled HP) was designed to hybridize with AFB aptamer to form double-stranded DNA, resulting in the opening of hairpin structure. When double-stranded DNA was modified on AuNSs surface, FAM was far from AuNSs and produced a strong fluorescence intensity. The introduction of AFB in the system led to the specific interaction of AFB and aptamer, and changed the conformation of aptamer, inducing the release of aptamer from double-stranded DNA and the restoration of hairpin structure. Fluorescence quenching occurred when FAM was close to AuNSs, and the fluorescence intensity decreased. In the presence of 5 ng/mL AFB, ΔF/F of the AuNSs/FAM-labeled HP/Apt was ~44.2%, higher than that of the AuNPs/FAM-labeled HP/Apt, indicating the better quenching effect of AuNSs. The change of fluorescence intensity linearly increased by adding AFB in the concentration range of 0.1 ng/mL-10 ng/mL, with the LOD of 21.3 pg/mL. The proposed aptasensor exhibited good selectivity in the presence of other toxins at 10-fold concentration of AFB, and showed satisfactory recovery in the range of 92%-112% toward AFB detection in spiked corn flour sample.