Encapsulation of proteinase K in PELA ultrafine fibers by emulsion electrospinning: Preparation and in vitro evaluation

The aims of this study were to encapsulate watersoluble bioactive agents into biodegradable hydrophobic polymers via emulsion electrospinning for drug delivery and tissue engineering applications and propose a simple and facile method to evaluate the bioactivity of the encapsulated protein. Proteinase K was selected as a model protein to be incorporated into poly(ethylene glycol)-poly (L-lactide) (PELA) ultrafine fibers. Core-shell structured fibers with single core or multi-core were observed. In vitro release study showed that after a burst release at the early stage, a sustained release was achieved, indicating that proteinase K was incorporated inside ultrathin fibers successfully. Results of in vitro incubation in Tris-HCl buffer at pH8.6 and 37°C revealed that electrospun PELA membranes containing proteinase K (PELA-P) showed obvious morphological changes, large mass loss, and slight decreases in melting temperature, melting enthalpy and relative molecular mass in 7 days. Additionally, a significant drop in pH value of the buffer after incubation of the PELA-P membrane was also observed. These findings clearly showed that encapsulation of water-soluble bioactive agents inside hydrophobic polymers could be achieved by emulsion electrospinning without compromising their bioactivity.