Cations influence the cross-linking of hydrogels made of recombinant, polyanionic spider silk proteins

Hydrogels made of polyanionic recombinant spider silk proteins (spidroins) were prepared either in the presence or the absence of Dulbecco's Modified Eagle Medium (DMEM). Mono- and divalent cations present in DMEM severely affected the self-assembly process of the spidroins. Although the addition of DMEM had no apparent effect on secondary structure formation, there was a significant effect on the kinetics as well as on the hydrogel network; in the presence of DMEM, gelation occurred more rapidly. Additionally, the hydrogels were stiffer; however, the hydrogels were still shear-thinning. In summary, it can be concluded that there is a significant impact of ionic cross-linking on recombinant spidroin-based hydrogels. (C) 2016 Elsevier B.V. All rights reserved.