Polyethylenimine (PEI)-decorated gold nanoparticles (AuNP) were electrodeposited on conductive surfaces in one-step procedure. Solution-state NMR evidenced that chloride from PEI.HCl was partially exchanged by AuCl4- prior to AuNP formation. XPS studies indicated the presence of Au degrees together with the interaction between AuNP with nitrogen atoms of the PEI polymer. The particle size by DLS was 49 nm. The electrochemical behavior of bare electrode and of glassy carbon electrode modified with PEI-decorated AuNP was compared using [Fe(CN)(6)](3-/4-) redox probe, to determine the potential role of the nanomaterial and of the polymer in the detection of proteins. The most relevant experimental variables from cyclic voltammetry (CV), square-wave voltammetry (SWV) and electrochemical impedance spectroscopy (EIS) were used for the characterization of protein uptake. The adsorption by electrostatic interaction between the biomolecules and the positively charged polymer (PEIH+) affected negatively the current response (Ip) of the probe, especially when the negatively charged protein was involved. This platform resulted adequate to immobilize proteins and to characterize this process, for further applications as a tool in bioanalysis or biotechnology. (C) 2019 Elsevier Ltd. All rights reserved.