Vortex-induced injectable silk fibroin hydrogels.
A novel, to our knowledge, technique was developed to control the rate of beta-sheet formation and resulting hydrogelation kinetics of aqueous, native silk solutions. Circular dichroism spectroscopy indicated that vortexing aqueous solutions of silkworm silk lead to a transition from an overall protein structure that is initially rich in random coil to one that is rich in beta-sheet content. Dynamic oscillatory rheology experiments collected under the same assembly conditions as the circular dichroism experiments indicated that the increase in beta-sheet content due to intramolecular conformational changes and intermolecular self-assembly of the silk fibroin was directly correlated with the subsequent changes in viscoelastic properties due to hydrogelation. Vortexing low-viscosity silk solutions lead to orders-of-magnitude increase in the complex shear modulus, G*, and formation of rigid hydrogels (G* approximately 70 kPa for 5.2 wt % protein concentration). Vortex-induced, beta-sheet-rich silk hydrogels consisted of permanent, physical, intermolecular crosslinks. The hydrogelation kinetics could be controlled easily (from minutes to hours) by changing the vortex time, assembly temperature and/or protein concentration, providing a useful timeframe for cell encapsulation. The stiffness of preformed hydrogels recovered quickly, immediately after injection through a needle, enabling the potential use of these systems for injectable cell delivery scaffolds.
Yucel
Tuna
T
Department of Biomedical Engineering, Tufts University, Medford, Massachusetts, USA.
Cebe
Peggy
P
Kaplan
David L
DL
D000818:Animals; D012831:Bombyx; D002942:Circular Dichroism; D004548:Elasticity; D005349:Fibroins / Q000008:administration & dosage* / Q000737:chemistry* / Q000378:metabolism; D020100:Hydrogels / Q000008:administration & dosage* / Q000737:chemistry* / Q000378:metabolism; D007267:Injections; D007700:Kinetics; D017433:Protein Structure, Secondary; D012212:Rheology; D033081:Shear Strength; D054457:Tissue Scaffolds / Q000737:chemistry*; D014783:Viscosity
D020100:Hydrogels; D005349:Fibroins