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-Ab1) and methylene blue sensitized QDs to combine a second antibody (MB/QDs-Ab2), 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-Ab1 led to a decreased photocurrent (ICry1Ab), while the subsequently anchored MB/QDs-Ab2 produced another photocurrent (IMB). 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 ICry1Ab and IMB 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.