Tunable release of hydrophilic compounds from hydrophobic nanostructured fibers prepared by emulsion electrospinning

The electrospinning process is a versatile technique for the encapsulation and controlled release of active substances. It also allows for the formation of various types of fiber microstructures such as porous or dense fibers, as well as core-sheath, co-continuous or hollow fibers. Herein, we aim at studying and controlling the release kinetics of a model substance from electrospun fibers in function of their morphology and composition. In this regard, we incorporated fluorescein sodium salt (FLU) as a model compound in fibers that were composed of polystyrene (PS) and polyvinylpyrrolidone (PVP) by electrospinning of inverse emulsions. We studied the effect of electrospinning parameters such as the relative humidity (RH%) and the surfactant concentration on fiber morphology, surface chemistry, wettability, membrane architecture, and release kinetics. Moreover, we demonstrate that fast release rates can be obtained when an emulsion is electrospun with an optimized surfactant concentration and at high relative humidity conditions. Such a combination yielded highly porous fibers with an average diameter of 2.4 +/- 0.7 mu m with ribbon-like cross sections. However, when the surfactant concentration was increased, dense fibers exhibiting slower release behavior were obtained. These results are a step forward in the systematization and control of release kinetics for non-woven membranes produced from electrospun emulsions. We demonstrate that both an accurate control of the fiber microstructure as well as the fiber composition is important to tailor the release kinetics of a model compound. (C) 2015 Elsevier Ltd. All rights reserved.