Platinum nanodendrite functionalized graphene nanosheets as a non-enzymatic label for electrochemical immunosensing

An ultrasensitive immunosensing method was developed using platinum nanodendrite functionalized graphene nanosheets (PtNDs@GS) as a non-enzymatic label for the electrochemical detection of human immunoglobulin G (HIgG). The PtNDs@GS hybrid was prepared in situ by reducing K₂PtCl₄ with ascorbic acid in an aqueous solution of reduced graphene oxide, and characterized by scanning electron microscopy, transmission electron microscopy and spectral techniques. The disposable immunosensor was constructed by coating a polyethylene glycol film on a screen-printed carbon working electrode and then immobilizing the capture antibody on the film. After binding with the antigen for further capture of the PtNDs@GS labelled antibody, PtNDs@GS was introduced as an electrochemical tag to produce a large electrocatalytic current towards the reduction of dissolved oxygen for signal amplification. Compared with the enzyme-based immunosensor, PtNDs@GS as non-enzymatic tag exhibited many advantages. This method showed a good linearity in the concentration range of 1 pg mL^-1 to 10 ng mL^-1, with a detection limit of 0.87 pg mL^-1. PtNDs@GS as non-enzymatic label provides a versatile method for constructing ultrasensitive immunosensors, and demonstrates proof-of-concept in immunosensing.