In this work, germanene and its derivatives (Ge-H, Ge-CH₃, Ge-C₃-CN) were explored as competitive immunoassays for the direct detection of gut-derived metabolites, kynurenic acid (KA) and quinolinic acid (QA) using disposable screen-printed carbon electrodes via impedance. The competition occurs between the free KA/QA standards and the BSA-conjugated antigens for a fixed amount of primary antibody binding sites. As a result, this affects the charge transfer resistance (R_ct) of the [Fe(CN)₆]^3-/4- redox couple at the electrode surface. Hence, the impedimetric signal measured due to the change in R_ct will be correlated to the KA and QA presence and concentration.