Tuning Emulsion Chemistry to Control Electrospun Fiber Morphology, Topography, and Drug Release

Abstract

Electrospinning is a complex fabrication technique capable of producing non-woven mesh with fiber diameters in the nanometer to micrometer scale. Applications for mesh with fibers at this scale are promising in many fields, including tissue engineering and drug delivery. Emulsion electrospinning is a subset of electrospinning and is particularly promising for drug delivery applications because it facilitates encapsulation of aqueously soluble drugs such as peptides and proteins and maintains the bioactivity of the encapsulated macromolecules. Although emulsion electrospinning has successfully been used to encapsulate macromolecules, a mechanistic understanding of how each compositional parameter in emulsions impact the resulting mesh characteristics has not been fully explored. The studies in this embodied work evaluate the effect of each component of emulsion solution chemistry on mesh characteristics. Specifically, solution chemistry components in water-in-oil emulsions, including the composition of the organic phase, the mobility and chemistry of surfactants, and the internal phase volume fraction, were evaluated. The effect of emulsion solution chemistry at varying relative humidity levels was also explored to determine the interrelated impacts of solution chemistry and humidity on the electrospinning process. Mesh characteristics of fiber morphology, surface topography, fiber volume fraction, and diameter were all evaluated because they are all capable of affecting cell response and drug release profiles. Drug release and drug loading of both a hydrophobic and hydrophilic model drug were also evaluated in systems created with different processing parameters. The results indicate that each component in an emulsion must be carefully selected for a given system, as they all affect mesh characteristics. The conductivity and evaporation of the organic phase solvent played a prominent role in determining the size and morphologies of electrospun fibers. The surfactant chemistry and ability to relocate to both the surface of the fibers and the interfacial areas was also important in producing meshes with controlled and consistent characteristics. The impact of internal phase volume fraction changed depending on other factors in the system, highlighting the sensitivity of an emulsion electrospinning system to its tuning parameters. The drug release and loading were both altered by surfactant, offering a view of how emulsion electrospinning could be used to tailor therapeutic release profiles. Including an internal phase improved burst effects for the hydrophilic model drug. Overall, these studies demonstrate the importance of compositional control of emulsions to dictate emulsion electrospun mesh characteristics. Tuning electrospun meshes with solution chemistry is a promising method for additional control of electrospun fibers and new areas of application such as drug delivery and cell response.