title: Effect of ionic strength on the interfacial viscoelasticity and stability of silk fibroin at the oil/water interface.
abstract: BACKGROUND
  The amphiphilic character and surface activity endows silk fibroin with the ability to reside at fluid interfaces and effectively stabilize emulsions. However, the influence of relevant factors and their actual effect on the interfacial viscoelasticity and stability of silk fibroin at the oil/water interface has received less attention. In the present study, the effect of ionic strength on the interfacial viscoelasticity, emulsification effectiveness and stability of silk fibroin at the oil/water interface was investigated in detail.
  
  
  RESULTS
  A higher ion concentration facilitates greater adsorption, stronger molecular interaction and faster structure reorganization of silk fibroin at the oil/water interface, thus causing quicker interfacial saturation adsorption, greater interfacial strength and lower interfacial structural fracture on large deformation. However, the presence of concentrated ions screens the charges in silk fibroin molecules and the zeta potential decreases as a result of electrostatic screening and ion-binding effects, which may result in emulsion droplet coalescence and a decrease in emulsion stability.
  
  
  CONCLUSIONS
  The positively-charged ions significantly affect the interfacial elasticity and stability of silk fibroin layers at the oil/water interface as a result of the strong electrostatic interactions between counter-ions and the negatively-charged groups of silk fibroin. © 2016 Society of Chemical Industry.
authors.affiliation: State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240, Shanghai, China.
authors.forename: Xiaoxiao
authors.initials: X
authors.lastname: Tang
authors.affiliation: State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240, Shanghai, China. xyqiao@sjtu.edu.cn.
authors.forename: Xiuying
authors.initials: X
authors.lastname: Qiao
authors.affiliation: Max Planck Institute of Colloids and Interfaces, Potsdam 14476, Germany.
authors.forename: Reinhard
authors.initials: R
authors.lastname: Miller
authors.affiliation: State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240, Shanghai, China.
authors.forename: Kang
authors.initials: K
authors.lastname: Sun
mesh_terms: D000327:Adsorption; D000818:Animals; D012831:Bombyx; D004355:Drug Stability; D004548:Elasticity; D004655:Emulsions / Q000737:chemistry*; D005349:Fibroins / Q000737:chemistry*; D009994:Osmolar Concentration; D012212:Rheology; D047011:Silk / Q000737:chemistry*; D055672:Static Electricity; D014783:Viscosity; D014867:Water / Q000737:chemistry
chemical_list: D004655:Emulsions; D047011:Silk; D014867:Water; D005349:Fibroins
keywords: emulsion; interfacial rheology; ionic strength; silk fibroin