Gold nanoparticle-based colorimetric aptasensor for rapid detection of multiple mycotoxins in rice

A novel, simple and rapid colorimetric aptasensor for multiple mycotoxins (ochratoxin A (OTA) and aflatoxin B₁ (AFB₁)) detection was developed using unmodified gold nanoparticles (AuNPs). In the work, the high affinities of OTA and AFB₁ aptamers were employed as the recognition elements for the colorimetric determination of OTA and AFB₁. In the absence of mycotoxins, the sulfhydryl-modified aptamers were directly adsorbed to the AuNP surface through Au-S bonds, further prohibiting the aggregation induced by a high concentration of salt, and the solutions remain red. In the presence of mycotoxins, the corresponding aptamer-target complexes were formed and the corresponding aptamers were detached from the surface of AuNPs, leading to the aggregation of AuNPs under the optimal salt solution and a color change. By spectroscopic quantitative analysis and visual analysis, the LODs of OTA and AFB₁ were down to 0.005 ng mL^-1 and 0.07 ng mL^-1, respectively. Furthermore, the colorimetric aptasensor showed a high specificity in the presence of other interfering mycotoxins and metal ions. Finally, the developed aptasensor was applicable to detect OTA and AFB₁ in rice samples with satisfactory performance. Our strategy has great potential for the rapid and sensitive detection of OTA and AFB₁ for on-site analysis.