In situ generation of ZnO nanoparticles within a polyethyleneimine matrix for antibacterial zein fibers

In this study the potential of branched polyethyleneimine (PEI) was explored for the in situ generation of ZnO nanoparticles and the electrospinning of zein-based fibers. Zinc acetyl acetonate dihydrate (ZnAcAc·2H2O) was chosen as the precursor for the related sol–gel reactions, leading to the nucleation and growth of wurtzite crystals within the PEI matrix. Control experiments showed that PEI played a vital role in the reaction steps leading to the conversion. Wide angle X-ray diffraction analysis confirmed the crystallographic structure of the ZnO particles formed, while scanning electron microscopy examinations revealed the formation of agglomerates less than 400 nm, made up of much smaller primary nanoparticles. The obtained ZnO/PEI microsuspensions in ethanol were mixed in an ethanol/water solution of zein and used for electrospinning of different types of zein-modified fibers. Differential scanning calorimetry analysis showed that PEI acted as a plasticizer for zein, causing also a broadening of the glass transition, while Fourier-transform infrared spectroscopy indicated that the amine groups in PEI interacted with the surface groups of ZnO crystals. The results provide useful insights for formulating fibers, films, and coatings exhibiting antibacterial characteristics, as well as higher mechanical flexibility and toughness relative to plain zein.