Surface plasmon coupling electrochemiluminescence assay based on the use of AuNP@C3N4QD@mSiO2 for the determination of the Shiga toxin-producing Escherichia coli (STEC) gene.

This work describes a surface plasmon coupling electrochemiluminescence (SPC-ECL) method for the determination of the Shiga toxin-producing Escherichia coli (STEC) gene. Firstly, gold nanoparticles (Au NPs) were encapsulated into a solid silica core (AuNP@SiO2). Secondly, graphite phase carbon nitride quantum dots (g-C3N4 QDs) were embedded in the mesoporous silica shell (mSiO2) to form nanospheres of type AuNP@C3N4QD@mSiO2. It is found that the surface plasmon coupling effect of the Au NPs in the solid silica core strongly enhances the ECL of the g-C3N4/K2S2O8 system. The mSiO2 carry much of the ECL luminophore (g-C3N4 QDs), and the co-reactant can readily pass the mesopores to react with QDs to give an ECL reaction. Because of these two features, the ECL is 3.8 times stronger compared to ECL sensing using g-C3N4 QDs only. Finally, AuNP@C3N4QD@mSiO2 was linked to the probe DNA to construct a competitive DNA sensor. When no target DNA is added, most of the capture DNA on the electrode is complementary to the probe DNA of AuNP@C3N4QD@mSiO2-probe DNA. At this time, the ECL signal is the strongest. When the target DNA is added, some of the capture DNA is paired with it and the remaining capture DNA is paired with the probe DNA. Consequently, less luminophore reaches the electrode and the signal is weaker. The method works in the 0.1 pM to 1 nM concentration range and has a 9 fM detection limit. It was successfully applied to the ultrasensitive determination of the STEC gene in human serum. Graphical abstract Schematic illustration for the "egg-yolk puff" structured ECL sensor based on Au NPs, g-C3N4 QDs, and mesoporous silica shell.