Development of zein nanofibers for the controlled delivery of essential amino acids for fish nutrition

Abstract

In the present paper, films and nanofibers of zein and zein/tryptophan were produced by casting and eletrospinning.The films and nanofibers were characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and controlled release and digestibility tests. In vitro releasing of tryptophan was evaluated using a spectrophotometer UV–Vis. Interactions between tryptophan and zein were confirmed by thermal (TGA) and spectral (FTIR) analyses. SEM micrographs provided evidence of a smooth and homogeneous structure for films and nanofibers without and with tryptophan. FTIR spectroscopy indicated second-degree intermolecular interactions between amide groups of zein and tryptophan. X-ray analysis indicated the formation of crystals that did not interfere with the crystallization of amino acid. By in vitro release experiments, it was possible to observe that the tryptophan releasing follows nearly Korsmeyer–Peppas model for the nanofibers and Peppas–Sahlin model for films, indicating the releasing process of the nanofibers are by diffusion of the amino acid and, for films, by relaxion of polymeric chain. Finally, in vitro digestibility a considerable amount of tryptophan was observed, suggesting more access of fishes for tryptophan.