The secondary structure control of silk fibroin thin films by post treatment

Silk fibroin (SF) thin film was prepared via colloid chemical routes (CC) and by pulsed laser deposition (PLD). Secondary structure of the CC film, as examined by FT-IR, was random coil. By a post treatment with methanol, it transforms to b-sheet. As for PLD films, the b-sheet structure of SF powder was mostly preserved as deposited. This suggests that the post treatment is effective to restore the original b-sheet structure in the thin films. Transformation from random coil to b-sheet is easier in the film on the substrate of polyethylene than Si(1 0 0) due to weaker affinity to silk fibroin.