Controlled release and enhanced bioavailability of curcumin using multilayered LPSG/PVA and zein/gluten nanofibers fabricated by emulsion electrospinning.

The low stability and bioavailability, and poor aqueous solubility of curcumin (Cur) make it difficult to fully utilize its biological benefits. To overcome these limitations, emulsion electrospinning technique was used to encapsulate Cur in multilayered nanofibers made of Lepidium perfoliatum seed gum (LPSG)/polyvinyl alcohol (PVA) as the middle layer, and zein or zein/gluten nanofibers as the outer layers. Cur was first dissolved in a corn oil/Tween 80 mixture to prepare the oil phase. For the middle layer, emulsions with LPSG/PVA (30:70 v/v) and corn oil (2, 5, 10 % v/v) were prepared. The emulsion's droplet size and consequently, the average diameter of electrospun nanofibers increased, while the encapsulation efficiency (EE%) of Cur decreased with increasing the oil phase content. The 2 % oil emulsion produced uniform, bead-free nanofibers with high EE% (92 %) and was selected for further multilayer fabrication. Protein nanofibers were then electrospun onto the LPSG/PVA nanofibers to form the outer layers. Atomic force microscopy (AFM) revealed stronger adhesion of zein nanofibers to the inner layer, resulting in more stable multilayered structures. Fourier-transform infrared (FTIR) spectroscopy confirmed successful physical encapsulation of Cur without chemical interactions between the layers. The thermal and photostability of Cur in the tri-layer nanofibers significantly increased, with the nanofibers containing an outer zein layer exhibiting higher stability compared to other samples. In vitro release studies showed that the multilayered nanofibers with zein as the outer layers provided the slowest release rate under simulated digestive conditions. The release behavior followed Fickian diffusion and was best fitted by the Kopcha model. Furthermore, the bioavailability of Cur increased up to 60 % in the multilayered nanofiber system with zein as the outer layers.