An electrochemical immunosensor based on polyaniline microtubules and zinc gallinate for detection of human growth differentiation factor-15

The incidence rate of cardiovascular diseases (CVDs) remains high, and their mortality rate is significantly higher than that of other diseases. Growth differentiation factor-15 (GDF-15) is a recently developed biomarker for the early diagnosis and prognostic evaluation of CVDs because its concentration in serum increases substantially after a cardiovascular injury or an inflammatory reaction. In this study, a sandwich-type immunosensor was constructed for the sensitive detection of GDF-15. Specifically, peony-like zinc gallinate (ZnGa₂O₄) prepared using a hydrothermal method, which exhibits excellent electrocatalytic performance, was coupled with Au nanoparticles (NPs) to obtain golden-peony-like ZnGa₂O₄/Au NPs. They preserved the immune activity of GDF-15 antibody molecules and further enhanced the conductivity, thereby realizing additional signal amplification. Hollow polyaniline (PANI) microtubules decorated with Pd NPs were used as the sensing platform (PANI/Pd NPs). The hollow microtubules provided abundant active sites and considerably improved the electron-transfer rate. Under optimal conditions, a linear range and remarkably low detection limit of 100 fg mL⁻¹–10 ng mL⁻¹ and 42.23 fg mL⁻¹, respectively, were achieved. These experimental results indicate that the strategy reported herein can be adopted as a novel approach for the convenient and rapid detection of GDF-15. Graphical abstract