3D label-free matrix metalloproteinase-3 immunosensor based on graphene oxide/polypyrrole-ionic liquid nanocomposite

Matrix metalloproteinase-3 (MMP-3) is a proteinase involved in the degradation of the extracellular matrix and it potentially plays an important role in metastasis development during the early stage of invasive cancers. In this work, a label-free electrochemical impedance immunosensor is for the first time developed for highly sensitive determination of MMP-3 based on the covalent immobilization of MMP-3 antibody on a 3D graphene oxide/polypyrrole-ionic liquid (GO/PPy-IL) composite film. The 3D GO/PPy-IL film was constructed by one-step electro-deposition of GO/PPy in 1-Butyl-3-methylimidazolium tetrafluoroborate (BMIm⁺BF^-₄ ) onto a silica opal template modified indium tin oxide (ITO) electrode, and showed high surface area, good biocompatibility and enhanced electronic conductivity. The MMP-3 concentration is measured through the relative increase of impedance values in corresponding specific conjugation of MMP-3 antigen with the MMP-3 antibody. Under the optimal conditions, the relative increased impedance values are proportional to the logarithmic value of MMP-3 concentrations in a linear range of 1 to 1000 pg ·mL^-1 with a low detection limit of 1 pg ·mL^-1. In comparison with current enzyme-linked immunosorbent assay, the MMP-3 immunosensor shows wider linear range, lower detection limit and simpler manipulation. Moreover, the immunosensor exhibits excellent selectivity, good stability, satisfactory reproducibility and regeneration. Such a 3D GO/PPy-IL film could have widespread applications in clinical screening of cancer biomarkers for point-of-care diagnosis.