Figure 4.

Possible applications of the reversible hydrogel–solution system: (a) Injectable property of silk hydrogel composed of nanofibers. (b,c) Water-insoluble scaffold composed of silk nanofibers through directly freeze-drying process. The silk nanofibers in our present system could be blended with fresh silk solution, and induce more nanofiber growth and stable conformation formation in fresh solution, resulting in water-insoluble nanofibrous scaffold formation. (d,e) Silk-modulated morphology control of CaCO₃ using silk with various nanostructures as templates. Sample d was regulated with ultrasonic-treated short nanofibers with length of about 200 nm, while sample e was controlled with ultrasonic-treated nanoparticles with length of about 50 nm. (f) The oriented growth of gold nanoparticles following silk nanofibers. The size of gold nanoparticles was easily controlled through adjusting gold forming conditions such as pH. (g) One-step synthesis of core–shell structure of Fe₃O₄–silk composite nanoparticles. The negative charge of silk shell provided enough repulsive force to restrain the aggregation of nanoparticles, endowing the nanoparticles excellent stability in aqueous solutions.