title: Structure and gelation mechanism of silk hydrogels.
abstract: Silk fibroin was regenerated from cocoons produced by the silkworm Bombyx Mori. Light scattering showed that an aqueous solution of the regenerated silk fibroin (RSF) was made of individual proteins with a weight average molar mass of about 4 x 10(5) g mol(-1) and a hydrodynamic radius of about 10 nm. Gel formation of RSF in acidic solutions was investigated as a function of the pH (2-4), concentration (0.5-10 g L(-1)) and temperature (5-70 degrees C). The structure of the gels was studied using light scattering and confocal laser scanning microscopy. The structure was found to be self-similar from length scales of less than 15 nm up to length scales of about 1 microm, and characterized by a correlation length of a few microns. Gel formation was tracked using turbidity, rheology, light scattering and circular dichroism. Gelation involves the formation of self-similar aggregates with a growth rate that increases exponentially. The protein aggregation is correlated to, and perhaps caused by, the formation of beta-sheets, the fraction of which also increases exponentially with time.
authors.affiliation: Complex Fluids and Polymer Engineering Group, Polymer Science and Engineering Division, National Chemical Laboratory, India-411 008.
authors.forename: Shailesh
authors.initials: S
authors.lastname: Nagarkar
authors.forename: Taco
authors.initials: T
authors.lastname: Nicolai
authors.forename: Christophe
authors.initials: C
authors.lastname: Chassenieux
authors.forename: Ashish
authors.initials: A
authors.lastname: Lele
mesh_terms: D000818:Animals; D012831:Bombyx / Q000378:metabolism; D002942:Circular Dichroism; D005349:Fibroins / Q000737:chemistry*; D020100:Hydrogels / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D012542:Scattering, Radiation; D047011:Silk / Q000737:chemistry*; D012996:Solutions / Q000737:chemistry; D013696:Temperature
chemical_list: D020100:Hydrogels; D047011:Silk; D012996:Solutions; D005349:Fibroins