Biodegradable Core/Shell Fibers by Coaxial Electrospinning: Processing, Fiber Characterization, and Its Application in Sustained Drug Release

Solutions of two biodegradable polymers, that is, poly(dl-lactic acid) (PDLLA) and poly(3-hydroxy butyrate) (PHB), were individually delivered to the inner and outer channel of a coaxial-tube spinneret for electrospinning to prepare core−shell fibers used for drug release applications. By interchanging the inner- and outer-channel solutions, either PDLLA/PHB or PHB/PDLLA core−shell fibers could be conveniently obtained. Their fiber diameters were readily controlled by the flow rate of the core fluid (Qc). The effects of Qc on the morphologies of the Taylor cone, the whipping jet, and the electrospun fibers were investigated. Several scaling laws describing the Qc dependence of the outer fiber diameter (Df) and the inner fiber diameter (df) were derived, that is, Df ∼ Qc0.02 and df ∼ Qc0.18 for the PDLLA/PHB fluids and Df ∼ Qc0.30 and df ∼ Qc0.59 for the PHB/PDLLA fluids. These scaling laws provided the processing guidelines for the manipulation of the final diameters of the core−shell fibers for a given p...