Assembled gold nanoparticles on nitrogen-doped graphene for ultrasensitive electrochemical detection of matrix metalloproteinase-2

A new electrochemical immunosensor was developed for ultrasensitive detection of matrix metalloproteinase-2 (MMP-2), which is one of the key biomarkers in blood. In our approach, an effective assembly of well-defined gold nanoparticles on nitrogen-doped graphene sheets was demonstrated. The composite facilitated robust immobilization of antibodies, promoted electron transfer and exhibited excellent electrochemical activity, which are suitable for biosensing. The design of the immunosensor also involved a polydopamine functionalized graphene oxide hybrid conjugated to horseradish peroxidase-secondary antibodies by covalent bonds as a multi-labeled and biocompatible probe to increase the electrochemical response. This novel signal amplification strategy with a sandwich-type immunoreaction significantly enhanced the sensitivity of detection of biomarkers. The proposed immunosensor displayed excellent analytical performance in the detection of MMP-2 ranging from 0.0005 to 50 ng mL⁻¹, with a detection limit of 0.11 pg mL⁻¹. Furthermore, it not only exhibited good stability with adequate reproducibility and accuracy, but also demonstrated efficiency in the detection of MMP-2 in real samples.