A highly sensitive competitive immunosensor based on branched polyethyleneimine functionalized reduced graphene oxide and gold nanoparticles modified electrode for detection of melamine.

Branched polyethyleneimine functionalized reduced graphene oxide (BPEIGn) was prepared by a one-step reaction, catalyzed by NaOH, using branched polyethyleneimine (BPEI) and graphene oxide (GO) without reductant hydrazine hydrate or sodium borohydride. The branched polyethylenimine acted as both a grafting agent and a reducing agent of GO. An competitive electrochemical immunosensor based on the Au/sodium mercaptopropanesulfonate/BPEIGn/gold nanoparticles/melamine (Au/MPS/BPEIGn/AuNPs/Mel) modified electrode was constructed for the determination of melamine. The double amplification of BPEIGn and AuNPs increased the sensitivity of the sensor. The melamine was detected by differential pulse voltammetry (DPV) in buffer solution (pH 7.4) containing K3(Fe(CN)6]/K4[Fe(CN)6]. Under optimized conditions, the proposed melamine immunosensor showed a linear relationship in the concentration range of 1 × 10-6 to 1 μM, with a detection limit of 2.66 × 10-7 μM.