Photoelectrochemical apta-biosensor for zeatin detection based on graphene quantum dots improved photoactivity of graphite-like carbon nitride and streptavidin induced signal inhibition

Zeatin is a kind of typical cytokinin, which plays important roles in regulating the proliferation and differentiation of plant cells, and widely distributed in various plant tissues. Herein, a simple and sensitive photoelectrochemical method was developed for zeatin detection using graphite-like carbon nitride (g-C 3 N 4 ) as photoactive material, graphene quantum dots as photoactivity improvement reagent, gold nanoparticles as immobilization substrate for DNA probe, DNA biotin labeled aptamer as zeatin recognition and streptavidin capture element, and streptavidin as PEC response inhibitor factor. In the presence of zeatin, DNA aptamer can bind with zeatin to form conjugate, which make aptamer releasing from electrode surface and decrease the capture amount of streptavidin, causing the increase of the PEC response. Under optimal conditions, the biosensor showed wide linear range from 0.1 to 100   nM and low detection limit of 0.031   nM (3σ). The developed method also presented good selectivity, even discriminating zeatin analogues. In addition, the proposed detection strategy can be further applied to detect zeatin in complex biological matrix, revealing great potential in practical applicability. This work might provide an excellent platform for zeatin or other phytohormone detection using aptamer as recognition reagent.