Gold nanoparticles decorated with a ferrocene derivative as a potential shift-based transducing system of interest for sensitive immunosensing.

The condensation of 1,1'-ferrocenedimethanol and lipoic acid yields a ferrocene derivative (FcD): 1,1'-ferrocenyl bis(methylene lipoic acid ester), a bipodant linker which was used to aggregate gold nanoparticles (AuNPs). The FcD/AuNP aggregations displayed a very well-resolved signal related to the ferrocene oxidation to ferrocenium. The aggregates were found to form an efficient transducing system for a novel concept of immunosensing based on the shifting of the ferrocene oxidation potential. αHIgG/FcD/AuNP or chicken αGIgG/FcD/AuNP bioconjugates are used along with carbon SPEs as an immunosensing platform for the detection of HIgG or GIgG as model analytes. As shown by CV and DPV, the antigens addition triggers significant anodic potential shifts (up to 75 mV) of the ferrocene oxidation peak as an immunoresponse for the Ag-Ab recognition. The results from selectivity and specificity experiments using bovine serum albumin, ovalbumin and α-lactalbumin as potentially interfering proteins to HIgG Ag showed that these potential shifts would be solely due to the Ag-Ab recognition events with excellent selectivity and specificity in the presence of up to 1000-fold of the competitive proteins.