Linear polyethylenimine-plasmid DNA nanoparticles are ototoxic to the cultured sensory epithelium of neonatal mice.

Polyethylenimine (PEI) has been demonstrated to be an effective non‑viral synthetic polymer for efficient gene delivery amongst various cell types in vitro and in vivo. In the present study, 25 kDa linear PEI (L‑PEI) was used to transfer plasmid DNA (pDNA), encoding the enhanced green fluorescent protein reporter gene, into the cultured cochlear epithelium of neonatal mice. The 25 kDa L‑PEI/pDNA nanoparticles were generated in phosphate‑buffered saline prior to transfection. Sensory epithelial cells were transfected using an appropriate weight ratio of L‑PEI and pDNA. However, the use of higher L‑PEI/pDNA ratios, which result in the generation of a greater number of nanoparticles, induced significant damage to the sensory epithelial cells, as demonstrated by immunofluorescent and transmission electron microscopy analyses. These results indicated that precautionary measures are required with regard to the use of PEI nanoparticles in nanomedicine, and emphasized the requirement for thorough physicochemical characterization and toxicity testing for each polymer vector prior to the construction of nanotechnology systems for use in clinical applications. The development of effective management techniques for potential nano‑ototoxicity risks is of considerable significance to the clinical applications of nanoparticles.