Structure for electro-spun silk fibroin nanofibers

Electro-spinning was made using bilk fibroin and it was found that silk fibroin nanofibers of partially oriented amorphous structure are producible using HFIP(1,1,1,3,3,3 hexafluoro-2-propanol) as a solvent for fibroin via the electro-spinning setup equipped with parallel electrodes as a collector. Transformation from amorphous to silk I of a highly contracted beta-turn form or amorphous to silk II of a regular array of antiparallel betasheets occurred preferentially via the treatment with water vapor or ethanol, respectively. In addition the c-axis of crystallites was oriented parallel to the fiber axis. When the electro-spinning was made using a dish-type collector filled with ethanol, a peculiar web texture was obtained. Such a web texture seems to be brought about by the shrinkage of fiber due to the crystallization of fibroin and/or surface tension of ethanol droplets formed between the fibers. In this spinning setup, the c-axis of crystallites was also oriented parallel to the fiber axis. (C) 2007 Wiley Periodicals, Inc.