Macroporous Silk Fibroin\nCryogels

Abstract

Silk fibroin cryogels with remarkable properties were\nobtained\nfrom frozen fibroin solutions (4.2–12.6%) at subzero temperatures\nbetween −5 and −22 °C. This was achieved by the\naddition of ethylene glycol diglycidyl ether (EGDE) into the cryogelation\nsystem. EGDE triggers the conformational transition of fibroin from\nrandom coil to β-sheet structure and hence fibroin gelation.\nOne of the unique features of fibroin cryogels is their elasticity\nthat allows them to resist complete compression without any crack\ndevelopment, during which water inside the cryogel is removed. The\ncompressed cryogel immediately swells during unloading to recover\nits original shape. The scaffolds obtained by freeze-drying of the\ncryogels consist of regular, interconnected pores of diameters ranging\nfrom 50 to 10 μm that could be regulated by the synthesis parameters.\nThe mechanical compressive strength and the modulus of the scaffolds\nincrease with decreasing pore diameter, that is, with decreasing gelation\ntemperature or, with increasing fibroin or EGDE concentrations in\nthe feed. The scaffolds produced at 12.6% fibroin exhibit a very high\ncompressive modulus (50 MPa) making them good candidates as bone scaffold\nmaterials.