Abstract: The present invention relates to a process for producing electrospun fibers comprising polyethyleneimine nanoparticles (PEIN). The use of PEIN permits the antibacterial finishing of electrospinnable polymers, provided that these polyethyleneimine nanoparticles are particles of derivatized polyethyleneimine (PEI), since pure underivatized PEI has no antibacterial action. Preference is given to using quaternized polyethyleneimine. The electrospinnable polymers can be coated with PEIN during and/or after the electrospinning. The polymeric fibers obtainable by the process according to the invention can be used for textile fibers, for example for the production of fibers for functional apparel or for fibrous nonwoven webs or fibrous mats for cell culture substrates.