Preparação e caracterização de nanofibras de zeína/poli (Óxido de etileno) por eletrofiação em solução

Abstract

Electrospinning is a widely used technique for the production of polymeric nanofibers. It is a simple and efficient method that can result in fibers with different morphologies, according to the used and controlled parameters. Zein is a natural, biocompatible and biodegradable polymer. Poly(ethylene oxide) (PEO) is a synthetic, biocompatible and non-toxic polymer. The combination of zein and PEO forming a polymer blend is an interesting strategy that can enable the production of a biomaterial with better properties than pure constituents. In this work zein/PEO fibers were obtained through solution electrospinning. The thermal behaviors of pure polymers and its mixtures were characterized through DSC, TGA and structurally by infrared spectroscopy (FTIR). Rheological analyzes were performed to verify the viscosity behavior of the solutions. The morphologies of the obtained fibers were analyzed by optical and electronic microscopies (MO and MEV), determining the average diameter of the fibers based in data collected from SEM images. The fractional factorial design 24-1 was used to evaluate the influences of four factors: PEO content in the blend; distance between needle tip and collector (working distance); electric applied tension; solution flow; on two responses: average fiber diameter and process yielding. The relationship between the PEO content in the blend and the fiber properties were evaluated by means of FTIR, DSC, TGA, tensile tests and cytotoxic tests. The concentration of the solution used for fiber production was set at 15% (polymer mass: solvent volume) in ethanol / water (80/20) (v/v). Two factorial envelops were performed, one with a PEO factor varied between 10 and 30% and another with this factor ranging from 2 to 82%. From the design with PEO content fixed between 10 and 30%, it was observed that the effect of this factor did not present statistical significance in the average fiber diameter response. However, when the PEO factor varied between 2 and 82%, its effect on that response became statistically significant. In addition, it was observed in both envelopes that the factor that exerts the greatest effect on the average fiber diameter response was the applied electrical voltage. The increase in PEO content in the blend caused a decrease in thermal stability and an increased the degree of fiber crystallinity. The mechanical tests showed that higher levels of zein are correlated with lower tensile strength of the fibers. This causes both elongation and Young's modulus increase. Thus, the presence of zein makes it possible to form more rigid fibers. The fibers presented cytocompatible characteristics, thus with potential for applications as a biomaterial. The control of the solution and process parameters in the electro-spinning technique proved to be essential for obtaining fibers with diameters at the micro and nanometric scale. Knowledge of the thermal, mechanical and biological properties of fibers are also essential to determine possible types of applications.