Biodegradable ultrafine fibers with core–sheath structures for protein delivery and its optimization

This study was aimed to design core–sheath‐structured polymeric fibers for protein delivery through emulsion electrospinning to enhance the encapsulation efficiency (EE), structural integrity, and activity retention, and to achieve controllable protein release. Integral core–sheath structure was achieved for electrospun fibers with lysozyme loading efficiency of 93.3% and the specific activity retention (SAR) of 64.6%, while the surface protein content (SP) was as low as 4.2%. The emulsion components were optimized to minimize the burst release and extend the release period, and the release profiles were found to be closely related with the fiber characteristics such as the SPs. An initial burst release as low as 6.2% followed by gradual release for 33 days was indicated from poly(ethylene glycol)‐poly(DL ‐lactide) (PELA) fibers. The gradual protein release was determined by a competition of fiber collapse leading to accelerated release and fiber fusion leading to decelerated release. Dependent on the matrix polymer and protein encapsulated, the degradation behaviors of the fiber matrices were correlated with the release rate and the effective lifetime of the drug release. The core–sheath‐structured ultrafine fibers could protect the structural integrity and bioactivity of encapsulated lysozyme, and an increase in the protective effect was demonstrated for fibers prepared from PELA matrix. Copyright © 2010 John Wiley & Sons, Ltd.