A sensitive sandwich-type immunosensor for the detection of MCP-1 based on a rGO-TEPA-Thi-Au nanocomposite and novel RuPdPt trimetallic nanoalloy particles

A novel electrochemical immunosensor was proposed for the detection of monocyte chemoattractant protein-1 (MCP-1), a biomarker of cardiovascular disease. Due to thionine (Thi) possessing electroactive redox properties, a one-step approach was utilized to synthesize a reduced graphene oxide-tetraethylene-thionine-Au (rGO-TEPA-Thi-Au) nanocomposite at room temperature using the synergistic effect of Thi and rGO-TEPA towards HAuCl4. We obtained the excellent matrix material, which immobilized more primary antibody MCP-1-Ab1 on rGO-TEPA on a modified glassy carbon electrode (GCE). To further enhance the sensitivity of the sensor, a novel signal generation and amplification strategy was developed for detection. RuPdPt trimetallic nanoalloy particles (RuPdPt TNPs), a novel nanomaterial, were synthesized by a one-pot method, displayed a uniform morphology as well as good electrochemical activity and bound with the secondary antibodies against MCP-1 via the Pt-NH2 bond. Most importantly, RuPdPt TNPs have a significant ability to catalyze H2O2 to produce an electron. The electrochemical signal was highly amplified because the electrochemical signal was primarily derived from the synergistic catalysis of H2O2 by RuPdPt TNPs and recorded by chronoamperometry. Under the optimal conditions, this newly designed biosensor exhibited sensitive detection of MCP-1 in the range from 20 fg mL−1 to 1000 pg mL−1, with a detection limit of 8.9 fg mL−1 (based on a S/N = 3). Additionally, the designed immunosensor showed acceptable selectivity, reproducibility and stability. This immunosensor is a promising strategy for analyzing clinical serum samples in the future.