Label-free paper-based electrochemical impedance immunosensor for human interferon gamma detection

Human interferon-gamma (IFN-γ) plays an important role in diagnosis of tuberculosis susceptibility, which is one of the crucial health problems worldwide. Here, a novel platform of paper-based microfluidic device coupled with label-free electrochemical impedance immunosensor was developed for sensitive detection of human IFN-γ. Polyaniline (PANI) was deposited on a graphene (G) screen-printed paper electrode by using cyclic voltammetry. The modified electrode provides high electrochemical conductivity and surface area for antibody immobilization, which significantly enhances the sensitivity. A linear relationship between impedance and logarithmic concentrations of human IFN-γ was found in a range of 5―1000 pg mL―1 with a detection limit (LOD) of 3.4 pg mL―1. Interestingly, the PANI-G modified electrodes display 31-fold higher sensitivity compared to PANI-modified electrodes. The PANI-G modified electrode was successfully applied to the determination of human IFN-γ in human serum with a good reproducibility. Moreover, the system offers several advantages including low cost, low sample volume requirement, disposability, and rapid analysis relative to traditional methods, allowing the platform to be used as an alternative tool for human IFN-γ screening.