Electrochemiluminescence immunosensor based on quenching effect of SiO2@PDA on SnO2/rGO/Au NPs-luminol for insulin detection

A sandwich quenching electrochemiluminescence (ECL) immunosensor was constructed for insulin detection. In this work, the SnO2/reduced graphene oxide/gold nanoparticles (SnO2/rGO/Au NPs) nanocomposites combined with luminol (Lu) were utilized to construct the base of the immunosensor, and the SiO2@Polydopamine (SiO2@PDA) nanomaterials acted as efficient ECL signal quencher. SiO2@PDA was firmly anchored secondary antibody (Ab2) by covalent bonding due to the reactive quinones at the surface of PDA film. Au NPs which functionalized SnO2/rGO were acted as the bridge to incubate with primary antibody (Ab1) by Au-N bond and simultaneously enhanced the sensitivity of immunosensor. In addition, we used the luminol-O2 system to obtain more stable ECL signal. Under the optimal experimental conditions, a reliable determination of insulin was realized within a linear range of 0.0001-50 ng/mL and with a detection limit of 26 fg/mL (S/N = 3). Therefore, the ECL immunosensor exhibited good sensitivity, acceptable selectivity and high repeatability. Meanwhile, the proposed sandwich quenching ECL immunosensor was also evaluated by detecting insulin in real samples, this immunosensor has potential application value in insulin detection.