Nano-inspired fibrous matrix with bi-phasic release of proteins.

Nanofibrous matrix was fabricated for the purpose of obtaining bi-phasic protein releases from a single protein delivery system. A block copolymer composed of poly(ethylene glycol) and poly(epsilon-caprolactone) was co-electrospun with protein solutions through a dual nozzle electrospinning system. Surface-exposed amine groups of the protein-encapsulating nanofiber at an aqueous phase were chemically conjugated to the carboxyl groups of another protein for surface-immobilization. The surface-immobilized proteins and the core-encapsulated proteins in the nanofibers were characterized by scanning electron microscopy and confocal microscopy. Encapsulation efficiency of protein in the core of the nanofiber was increased when poly(vinyl alcohol) was mixed in the protein solution. Flow rate ratios of protein solutions to polymeric solutions significantly affected encapsulation efficiency of proteins in the nanofiber, where high flow rate ratios increased encapsulation efficiencies of proteins in the nanofiber. Release profiles of the immobilized proteins and the encapsulated proteins from the nanofiber were examined for 4 days. The encapsulated proteins showed initial burst profiles while the surface-immobilized proteins showed no or minimal release of proteins for the release period. Thus, the nano-inspired fibrous matrix can be potentially employed to fabricate a drug delivery device with a bi-phasic release profile of proteins.