Formation of Core–Shell Structures in Emulsion Electrospun Fibres: A Comparative Study

Abstract

Electrospinning has attracted great attention in recent years from different industries including biomedical engineering. Owing to the relative ease of fabricating ultrafine fibres with core-shell structures, emulsion electrospinning has been investigated intensively for making nanofibrous delivery vehicles for local and sustained release of bioactive or therapeutic substances, especially biomolecules such as growth factors. In preparing emulsions for electrospinning, different surfactants, ionic or non-ionic, can be used, which may subsequently influence the evolution of the core-shell structure in the electrospun emulsion jet or fibre. In this investigation, emulsions consisting of deionized water or phosphate buffer saline as the water phase, a poly(lactic-co-glycolic acid) solution as the oil phase and Span 80 (a non-ionic surfactant) or sodium dodecyl sulfate (an ionic surfactant) were electrospun into fibres for studying the core-shell structure and its evolution in emulsion electrospun fibres. Different microscopies were employed to study the morphological changes of the water phase in fibre samples collected at different locations along the jet (or fibre) trajectory during emulsion electrospinning. It was found that the evolution of the fibre core-shell structure was significantly different when different surfactants were used. If Span 80 was the surfactant, the water phase within the thick emulsion jet (or fibre) close to the Taylor cone existed in a discrete state whereas in ultrafine fibres collected beyond a certain distance from the Taylor cone, a mostly continuous water-phase core was observed. If sodium dodecyl sulfate was the surfactant, the core-shell structure in the thick jet (or fibre) was irregular but relatively continuous. A single core core-shell structure was eventually developed in ultrafine fibres. The core-shell structure in electrospun fibres and its evolution were also affected by the emulsion composition (e.g. polymer solution concentration, water-phase volume, and ion addition in the water phase).

Effect of Ionic and Non-Ionic Surfactant on Bovine Serum Albumin Encapsulation and Biological Properties of Emulsion-Electrospun Fibers

“…Due to the microstructure of fibrous substrates resembling the extracellular matrix, electrospinning is one of the most extensively researched and developed methods. Moreover, apart from providing physical and/or chemical stimuli for cell adhesion, electrospun scaffolds are good carriers for targeted drug delivery [ 1 ]. Due to the high surface-to-volume ratio, the fibrous carrier can be used not only for the delivery of drugs but also of biomolecules such as proteins, peptides, growth factors, genes, hormones, etc.…”

Fabrication and Thermal Insulation Properties of Bamboo‐Shaped Polymer Fibers by Selective Solvent Vapor Annealing

“…[29,30] It has been studied that, to avoid the shear forces generated during the whipping process, the components with lower viscosities in the blend solutions aggregate near the surfaces of the jets, forming the shell of the core-shell fibers; [31][32][33] the components with higher viscosities in the blend solutions assemble in the center parts of the jets, forming the core of the core-shell fibers. [34][35][36] The morphologies of the electrospun PS/PMMA core-shell fibers can be observed in Figure S1, Supporting Information. From the broken edge of a fiber, the solid nature of the fibers can be seen ( Figure S1a, Supporting Information).…”

“…Kinetic factors, such as mobility and rapid solvent evaporation, are also crucial for the phase separation process . It has been studied that, to avoid the shear forces generated during the whipping process, the components with lower viscosities in the blend solutions aggregate near the surfaces of the jets, forming the shell of the core‐shell fibers; the components with higher viscosities in the blend solutions assemble in the center parts of the jets, forming the core of the core‐shell fibers . The morphologies of the electrospun PS/PMMA core‐shell fibers can be observed in Figure S1, Supporting Information.…”

Plateau–Rayleigh Instability Morphology Evolution (PRIME): From Electrospun Core–Shell Polymer Fibers to Polymer Microbowls

“…In the emulsion electrospinning process, emulsions are used with a single nozzle. The dispersed phase in the emulsion becomes the core of the electrospun fibers and the continuous phase turns into the shell …”