Engineering the Signal Transduction between CdTe and CdSe Quantum Dots for in Situ Ratiometric Photoelectrochemical Immunoassay of Cry1Ab Protein.

Controllable modulation of a response mode is extremely attracting to fabricate biosensor with programmable analytical performances. Here, we reported a proof-of-concept ratiometric photoelectrochemical (PEC) immunoassay of Cry1Ab protein based on the signal transduction regulation at the sensing interface. A sandwich-type PEC structure was designed so that gold nanorods sensitized quantum dots to fix primary antibody (Au NRs/QDs-Ab 1 ) and methylene blue sensitized QDs to combine a second antibody (MB/QDs-Ab 2 ), which served as photoelectric substrate and signal amplifier, respectively. Unlike common recognition element, such a sandwich-type PEC structure allowed for the in situ generation of two specific response signals. For analysis, Cry1Ab captured by Au NRs/QDs-Ab 1 led to a decreased photocurrent ( I Cry1Ab ), while the subsequently anchored MB/QDs-Ab 2 produced another photocurrent ( I MB ). Noteworthy, by taking advantage of the different energy band gaps of QDs, varying locations of CdTe and CdSe QDs could realize different signal transduction strategies (i.e., Mode 1 and Mode 2). Investigations on data analysis of I Cry1Ab and I MB via different routes demonstrated the superior analytical performances of ratiometry (Mode 1). Consequently, the ratiometric PEC immunosensor offered a linear range of 0.01-100 ng mL -1 with a detection limit of 1.4 pg mL -1 . This work provides an efficient strategy for in situ collection of multiple photocurrents to design ratiometric PEC sensors.