Electrospun Potato Protein Isolate Nanofibers as a Solid Formulation for Improved Aqueous Apparent Solubility of Curcumin

This study reports a solid formulation consisting of electrospun nanofibers based on potato protein isolate (PPI), which facilitates the incorporation and release of soluble and active curcumin. The processing of the poorly water-soluble model compound curcumin into a solid dispersion of electrospun nanofibers was achieved from a water-based solution with only minute amounts (10% (v/v)) of ethanol. This was possible due to the presence of a high concentration of PPI that arrests the precipitation of curcumin. The cospinning polymer polyethylene oxide (PEO) was added to facilitate the electrospinning process. The electrospun curcumin-loaded PPI/PEO nanofibers displayed a uniform morphology with a size distribution centered around 479 ± 129 nm and contained a very small amount of residual solvent (recorded weight loss of 4.7 ± 0.3%, as analyzed by thermogravimetric analysis). After dissolution of the curcumin-loaded nanofibers in pure water, 52 ± 3% of curcumin was solubilized corresponding to a ∼40x improvement in its reported aqueous apparent solubility as quantified by a calibration curve of curcumin made in 90% (v/v) water and in the presence of PPI and PEO. Finally, an antibacterial assay confirmed that curcumin was not only solubilized but also remained active upon processing as demonstrated by inhibition of the growth of Escherichia coli.