A sensitive fluorescent DNA hydrogel aptasensor based on the self-assembly of rolling circle amplification (RCA) products was developed for ochratoxin A (OTA) detection in beer. A competitive binding mode of aptamer, complementary sequence, and target was integrated into the DNA hydrogel for OTA detection. The OTA aptamer first combined with the primer to form the hybridized product. Then, in the presence of OTA, the aptamer combined with OTA, which released the primer. The released primer hybridized with the padlock probe to form a circular template, and the RCA reaction was initiated by adding ligase, polymerase, and dNTPs. The fluorescent DNA hydrogel was obtained by adding Cy3-dUTP together with dNTPs, and the fluorescence (FL) intensity of the DNA hydrogel was positively correlated with OTA concentration. Under the optimal experimental conditions, the linear range of the relationship varied from 0.05 ng/mL to 100 ng/mL with a detection limit for OTA of 0.01 ng/mL. The fluorescent DNA hydrogel aptasensor showed good specificity and stability in beer samples. Therefore, the fabricated DNA hydrogel aptasensor shows considerable potential applications in detecting OTA for food safety.
Keywords: DNA hydrogel; OTA; aptamer; rolling circle amplification.