Room-temperature ionic liquid assisted fabrication of sensitive electrochemical immunosensor based on ordered macroporous gold film

A novel label-free highly sensitive electrochemical impedance spectroscopy (EIS) immunosensor was fabricated based on the highly ordered macroporous gold film (HOMGF) in the presence of room-temperature ionic liquid (IL) for the detection of human Apolipoprotein B-100 (ApoB-100). The antibody of ApoB-100 (Ab) was adsorbed directly onto the HOMGF electrode surface and maintained its bioactivity. After the residual active sites at the electrode were passivated by BSA, the mixture of BMIm⁺BF₄^- and silica sol was dropped onto the electrode to entrap the adsorbed Ab and BSA molecules firmly. The addition of IL could prevent the inactivation of Ab by releasing alcohol during the sol-gel process, and the conductivity of the IL-gel membrane was increased. Of particular interest is the fact that the fabricated immunosensor could be used at 60 °C. This could be attributed to the interconnected porosity of the IL-gel membrane, which can prevent Ab from unfolding and losing its bioactivities. The immunosensor also exhibited a highly sensitive response to ApoB-100 with the lowest concentration of 5 fg mL ^-1. The detection of ApoB-100 levels in five sera samples obtained from hospital showed acceptable accuracy with that using commercial immunonephelometry method.