Multifunctional bilayer films based on pea protein isolate and alginate with Fe₃O₄ nanoparticles

The objective of the present study was to develop multifunctional bilayer films for sustainable applications using a pea protein isolate (PPI)-alginate (AL) base layer and an electrospun PPI-polyvinyl alcohol (PVA) fiber layer containing Fe₃O₄ nanoparticles. This research systematically investigated the effects of varying Fe₃O₄ nanoparticle concentrations (0 %, 3 %, 6 %, 9 %, and 12 %) on the properties of bilayer films, as well as the surface tension and electrical conductivity of the electrospinning solution. Strong interactions between Fe₃O₄ nanoparticles and the electrospun PPI-PVA fibers were confirmed by FTIR and XRD analyses, resulting in enhanced thermal stability, mechanical properties, and barrier performance with increasing nanoparticle concentration. For instance, tensile strength, water vapor permeability (g·m^-1·Pa^-1·s^-1), and oxygen permeability (g·m^-2·s^-1) of the nanoparticle-free film were 36.7 MPa, 1.04 × 10^-9, and 0.68 × 10^-3, respectively, which changed to 39.4 MPa, 0.56 × 10^-9, and 0.41 × 10^-3, respectively, at 12 % nanoparticle concentration. FESEM analysis confirmed the formation of smooth nanofibers at low concentrations, while higher concentrations resulted in irregular fiber morphology and bead formation. The increase in electrical conductivity and reduction in surface tension of the electrospinning solution with higher Fe₃O₄ nanoparticle concentrations led to an increase in the diameter of the electrospun PPI-PVA fibers. Enhanced functional properties, including antioxidant and antimicrobial activities, were observed with increasing concentrations of Fe₃O₄ nanoparticles. Biodegradability studies confirmed the environmental compatibility of the developed bilayer films, highlighting their potential use in sustainable and eco-friendly applications.