Lithium-free processing of silk fibroin.
Silk fibroin protein was purified from Bombyx mori silkworm cocoons using a novel dialysis strategy to avoid fibroin aggregation and pre-mature formation of β-sheets. The degummed silk fibers were dissolved in Ajisawa's reagent, a mixture of CaCl2-EtOH-H2O, that is less expensive than lithium bromide. The dissolved solutions were dialyzed against either water or urea solution with a stepwise decrease in concentration. When the steps of 4 M-2 M-1 M-0 M urea (referred to as silk-TS-4210) were adopted, the purified silk fibroin had smaller aggregates (<10 nm), similar average molecular weight (225 kDa) and a lower content of β-sheet (∼15%) compared to the sample processing methods (silk-TS-210, 10, 0) studied here. This outcome was close to the fibroin purified by the lithium bromide (silk-Li-0) method. Polyvinyl alcohol-emulsified silk microspheres generated using the purified solution had a similar size distribution and morphology when compared to lithium bromide dissolved solutions, while glycerol-blended silk films showed different mechanical properties. The silk-Li-0 generated films with the highest breaking strength (5.7 MPa ± 0.3) while the silk-TS-4210 had the highest extension at break (215.1% ± 12.5). The films prepared from silk-TS-4210 were cytocompatible to support the adhesion and proliferation of human mesenchymal stem cells, with improvements compared to the other samples likely due to the porous morphology of these films.
National Engineering Laboratory for Modern Silk, College of Textile and Clothing Engineering, Soochow University, Suzhou, China.
Zhaozhu
Z
Zheng
National Engineering Laboratory for Modern Silk, College of Textile and Clothing Engineering, Soochow University, Suzhou, China.
Shaozhe
S
Guo
National Engineering Laboratory for Modern Silk, College of Textile and Clothing Engineering, Soochow University, Suzhou, China.
Yawen
Y
Liu
National Engineering Laboratory for Modern Silk, College of Textile and Clothing Engineering, Soochow University, Suzhou, China.
Jianbing
J
Wu
National Engineering Laboratory for Modern Silk, College of Textile and Clothing Engineering, Soochow University, Suzhou, China.
Gang
G
Li
National Engineering Laboratory for Modern Silk, College of Textile and Clothing Engineering, Soochow University, Suzhou, China.
Meng
M
Liu
National Engineering Laboratory for Modern Silk, College of Textile and Clothing Engineering, Soochow University, Suzhou, China wangxiaoqin@suda.edu.cn.
Xiaoqin
X
Wang
Tufts University, Medford, MA, USA.
David
D
Kaplan
D000818:Animals; D001672:Biocompatible Materials / Q000008:administration & dosage / Q000138:chemical synthesis* / Q000302:isolation & purification; D012831:Bombyx / Q000737:chemistry*; D001965:Bromides / Q000737:chemistry; D002448:Cell Adhesion / Q000502:physiology; D049109:Cell Proliferation / Q000502:physiology; D002478:Cells, Cultured; D005349:Fibroins / Q000008:administration & dosage / Q000138:chemical synthesis* / Q000302:isolation & purification; D006801:Humans; D007202:Indicators and Reagents / Q000737:chemistry; D018020:Lithium Compounds / Q000737:chemistry; D008422:Materials Testing; D059630:Mesenchymal Stem Cells / Q000187:drug effects* / Q000502:physiology; D047011:Silk / Q000737:chemistry*; D014508:Urea / Q000737:chemistry*
D001672:Biocompatible Materials; D001965:Bromides; D007202:Indicators and Reagents; D018020:Lithium Compounds; D047011:Silk; C040949:lithium bromide; D014508:Urea; D005349:Fibroins
Ajisawa’s reagent; Silk fibroin; gradient dialysis; lithium bromide; urea