Environmentally benign synthesis of electrospun collagen-I in acetic acid solution

Type-I collagen nanofibers were electrospun from aqueous collagen solution using acetic acid solution as a solvent, which is a replacement for 1,1,1,3,3,3 hexafluoro-2-propanol. A uniform nanofibrous mat of average fiber diameter of 120 nm was obtained from the following optimum condition: 14.3 mg/ml of collagen solution in aqueous 6% acetic acid solution with adding 10 wt% polyvinylpyrrolidone ethanol solution was successfully electrospun in the electric field of 17 kV. The aqueous acetic acid concentration higher than 2% was prerequisite for collagen nanofiber formation, because more concentrated acetic acid in water progressively decreased surface tension of the collagen solution and concomitantly increased charge density of jet without significant effect on solution viscosity. However, acetic acid solution more than 6% did not dissolve enough collagen to make spinnable viscous concentration. Only a mass ratio 1/5 of polyvinylpyrrolidone and collagen in the electrospinning solution produced bead-free collagen nanofibers, while low- or high-mass ratio of polyvinylpyrrolidone did not.