Nerve Growth Factor‐Binding Engineered Silk Films Promote Neuronal Attachment and Neurite Outgrowth

Spider silks have outstanding potential as biomaterials due to their sought-after mechanical properties and low immunogenicity. The toughest spider silk is aciniform silk, which is used by spiders to wrap prey and produce egg sacs. A variety of recombinant aciniform silk constructs are now been developed, including hybrid silks with domains from multiple spider silk proteins fused together. In this study, an engineered aciniform silk construct, termed N(B)Silk, fused both N- and C-terminally to heptapeptide motifs that bind the neurotrophic factor and nerve growth factor-beta (NGF) is introduced. N(B)Silk is shown to be amenable to casting into robust films that remain intact while sequestering and maintaining bioactive NGF at the film surface for at least 7 days. These films support cell survival while enhancing differentiation and neurite density and outgrowth in neuron-like PC12 cells, with elevation of signaling through both the mitogen-activated protein kinase (MAPK) and protein kinase B (AKT) signaling pathways. Strikingly, preloading of N(B)Silk films with NGF enhances neuritogenesis even over conditions where cells are grown with NGF supplementation in the culture medium. N(B)Silk scaffolds, thus, warrant future development and evaluation as biomaterials for nerve regeneration.