This study reports the effects of treatment with various concentrations of organic solvents for varying time points on matrices of fibroin, a silk protein isolated from the mulberry silkworm, Bombyx mori, which in native form has been extensively used in tissue engineering. Treatment of pure fibroin as well as polyethylene glycol- blended films with 90% organic solvent for 60 min induces optimal surface hydrophobicity and maximum conversion of the secondary structure from random coil to β sheet. Long-term cell viability studies reveal that methanol and isopropanol-treated pure and blended films support cell adhesion, proliferation, and viability.