The process of obtaining the composite layer consisting of conductive copolymer, composed of unmodified pyrrole and pyrrole-3-carboxylic acid units (in various molar ratio) in combination with magnetic nanoparticles was investigated using voltammetry, scanning electron microscopy, transmission electron microscopy, scanning transmission electron microscopy and surface enhanced Raman scattering (SERS) spectroscopy. The SERS and voltammetric data demonstrate that the use of molar concentration ratio of monomers 75 (Py) to 25 mM (Py-COOH) results in the conductive polymer layer with the best bioelectrochemical properties. The ferritin attached covalently to such composite demonstrated the highest electroactivity. Thus, mixed conductive copolymer film containing Py and Py-COOH units, combined with magnetic nanoparticles could be further useful in developing bioactive conductive platforms for specific biomedical purposes. (c) 2018 Elsevier Ltd. All rights reserved.