A ratio electrochemiluminescence sensor for monitoring amyloid-beta based on g-C3N4-heme with luminol as the internal standard

Monitoring of the amyloid-beta (A β ) peptide is crucial for the diagnosis and treatment of Alzheimer’s disease. Here, a label-free, signal-on ratiometric electrochemiluminescence (ECL) aptasensor was fabricated for the detection of A β peptide. Specifically, graphite-like carbon nitride (g-C 3 N 4 ) nanosheets and luminol served as the cathodic and anodic ECL emitters, respectively. K 2 S 2 O 8 and H 2 O 2 were used as the coreactants for the two emitters. Luminol was first coated on the indium tin oxide (ITO) electrode and used as the internal standard in the ratiometric biosensor. Polyaniline was then electrodeposited on the surface of the luminol-modified electrode to improve the biocompatibility and conductivity of the sensing interfaces. Gold nanoparticles were subsequently modified on the surface of polyaniline to immobilize a DNA aptamer. g-C 3 N 4 -heme incubated with different concentrations of A β solution to form g-C 3 N 4 -heme-A β complex, in which A β could specifically bind to the DNA aptamer and thus introduce g-C 3 N 4 into the system. As a result, it was observed that the ratio value of ECL intensity ( I 1 / I 2 ) significantly increased with the increase of A β concentration. Under the optimized conditions, the biosensor has a good linear response in the range 10 fM to 10 nM with a detection limit of 4.2 fM. Consequently, the ratiometric ECL sensor, characterized by high sensitivity and favorable stability, offers a reliable method for the determination of A β . Graphical