Poly(ethylene glycol) (PEG)-silk fibroin (SF) conjugate (PEGI-SF) was
prepared by the chemical modification of solubilized SF with 2-[O-meth
oxypoly(ethylene glycol)]-4,6-dichloro-s-triazine (actPEG1), and the p
hysical properties of the PEG1-SF film were studied. The circular dich
roism (c.d.) spectrum of the PEG1-SF him exhibited both negative and p
ositive extrema due to a beta-sheet structure. D.s.c. measurements and
polarizing microscopic observations at elevating temperature of the P
EG1-SF film clarified the thermal behaviour of the PEG1-SF film exhibi
ting the melting of the PEG chains and the decomposition of SF. In the
d.s.c. thermogram of PEG1-SF, the positions of the endothermic peaks
due to the melting of the PEG chains and the decomposition of SF scarc
ely shifted compared to the peak position of actPEG I and the peak pos
ition of the SF having a beta-sheet structure, respectively. Judging f
rom these observations, the mutual miscibility between PEG and SF was
considered to be poor. The tensile tests of the PEGI-SF and SF films r
evealed that the PEG-modification of SF improved the elongation at bre
ak but reduced the tensile strength. based on these results, a layered
structure of the PEG1-SF film was suggested. Copyright (C) 1996 Elsev
ier Science Ltd.