title: Silk fibroin gelation via non-solvent induced phase separation.
abstract: Tissue engineering benefits from novel materials with precisely tunable physical, chemical and mechanical properties over a broad range. Here we report a practical approach to prepare Bombyx mori silk fibroin hydrogels using the principle of non-solvent induced phase separation (NIPS). A combination of reconstituted silk fibroin (RSF) and methanol (non-solvent), with a final concentration of 2.5% w/v and 12.5% v/v respectively, maintained at 22 °C temperature turned into a hydrogel within 10 hours. Freeze-drying of this gel gave a foam with a porosity of 88%, a water uptake capacity of 89% and a swelling index of 8.6. The gelation kinetics and the loss tangent of the gels were investigated by rheometry. The changes in the morphology of the porous foams were visualized by SEM. The changes in RSF chemical composition and the relative fraction of its secondary structural elements were analyzed by ATR-FTIR along with Fourier self-deconvolution. And, the changes in the glass transition temperature, specific heat capacity and the relative fraction of crystallinity of RSF were determined by TM-DSC. Data suggested that RSF-water-methanol behaved as a polymer-solvent-non-solvent ternary phase system, wherein the demixing of the water-methanol phases altered the thermodynamic equilibrium of RSF-water phases and resulted in the desolvation and eventual separation of the RSF phase. Systematic analysis revealed that both gelation time and the properties of hydrogels and porous foams could be controlled by the ratios of RSF and non-solvent concentration as well as by the type of non-solvent and incubation temperature. Due to the unique properties we envisage that the herein prepared NIPS induced RSF hydrogels and porous foams can possibly be used for the encapsulation of cells and/or for the controlled release of both hydrophilic and hydrophobic drugs.
authors.affiliation: Department of Biomaterials and Bioanalogous Polymer Systems, Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, v.v.i., Prague, Czech Republic. kasoju@imc.cas.cz kubies@imc.cas.cz and Department of Zoology, University of Oxford, Oxford, UK. fritz.vollrath@zoo.ox.ac.uk.
authors.forename: Naresh
authors.initials: N
authors.lastname: Kasoju
authors.affiliation: Department of Zoology, University of Oxford, Oxford, UK. fritz.vollrath@zoo.ox.ac.uk.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Hawkins
authors.affiliation: Department of Chemistry and Physics of Surfaces and Biointerfaces, Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, v.v.i., Prague, Czech Republic.
authors.forename: Ognen
authors.initials: O
authors.lastname: Pop-Georgievski
authors.affiliation: Department of Biomaterials and Bioanalogous Polymer Systems, Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, v.v.i., Prague, Czech Republic. kasoju@imc.cas.cz kubies@imc.cas.cz.
authors.forename: Dana
authors.initials: D
authors.lastname: Kubies
authors.affiliation: Department of Zoology, University of Oxford, Oxford, UK. fritz.vollrath@zoo.ox.ac.uk.
authors.forename: Fritz
authors.initials: F
authors.lastname: Vollrath
mesh_terms: D000818:Animals; D001672:Biocompatible Materials / Q000737:chemistry*; D012831:Bombyx / Q000737:chemistry*; D005349:Fibroins / Q000737:chemistry*; D020100:Hydrogels / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D016062:Porosity; D012997:Solvents / Q000737:chemistry*; D013696:Temperature; D023822:Tissue Engineering
chemical_list: D001672:Biocompatible Materials; D020100:Hydrogels; D012997:Solvents; D005349:Fibroins