Laser-induced graphene based ratiometric electrochemical aptasensor enabled by the sandwich-type bioreceptor for efficient detection of 17β-estradiol

Sandwich-type biosensor allows better accuracy for detection, yet dual recognition with two free bioreceptors is prone to interference and requires extended assay time. This study reported a ratiometric electrochemical aptasensor with a confined sandwich structure via the reunion of two split aptamers for 17β-estradiol (E2) detection. A sandwich-type bioreceptor was synthesized to confine dual recognition by connecting two split aptamers with thymine (T) bases, and the number of T bases showed significant influence on its performance. For biosensing, the ferrocene (Fc)-labelled sandwich-type bioreceptor caught E2 to produce an enlarged current signal of Fc (I Fc ); methylene blue (MB)-loaded zeolitic imidazolate framework-8 nanocomposite, absorbed by porous laser-induced graphene to act as substrate electrode, output a stable current signal of MB (I MB ) for reference. Using I Fc /I MB as a yardstick, the fabricated ratiometric electrochemical aptasensor offered a linear range of 10 pg mL −1 -500 ng mL −1 with a detection limit of 7.60 pg mL −1 for E2 detection as well as high selectivity, stability, and reproducibility. The sandwich-type bioreceptor by split aptamer reunion provided a high-performance recognition element for biosensors, and this work should pave a new way to obtain highly efficient bioreceptors.