Preparation and characterization of hollow polyurethane nanofiber and its application in in-situ encapsulation of enzyme

Hollow polyurethane (PU) nanofiber was prepared by co-axial electrospinning with glycerol containing certain content of water and PU dissolved in organic solvent as internal and external phase electrospinning solutions, respectively. The effects of the solution composition and flow rate, and diameter of co-axial spinneret on the morphology, mechanical strength and surface wetability of the nanofiber were investigated. The results showed that uniform hollow PU nanofiber was successfully fabricated by co-axial electrospinning glycerol containing 5%(φ) water and N, N-dimethylacetamide solution of 30%(ω) PU as internal and external phase electrospinning solution under the conditions of the solution flow rates of 0.07 and 0.5 mL/h, voltage 17 kV, distance between spinneret and collector 25 cm, temperature 25°C, and humility 10%. Hollow PU nanofiber prepared under above conditions had membrane tensile strength of 3.9 MPa and elongation at break of 332.8%, and contact angle with water of 100.2°. By dissolving definite amount of horseradish peroxidase (HRP) in the internal phase electrospinning solution, the enzyme was in-situ encapsulated inside the hollow channel of PU nanofiber. The kinetic biocatalytic activity of encapsulated HRP showed that an activity recovery rate of 80% was obtained, and similar Michaelis-Menten constant, K_m, was observed for the free and encapsulated HRP. Thermal stability of HRP showed that the half-life of HRP at 60°C was prolonged about 17 times after encapsulation.