Site‐Specific Functionalization of Recombinant Spider Silk Janus Fibers

Biotechnological production is a powerful tool to design materials with customized properties. The aim of this work was to apply designed spider silk proteins to produce Janus fibers with two different functional sides. First, functionalization was established through a cysteine‐modified silk protein, ntag(Cys)eADF4(κ16). After fiber spinning, gold nanoparticles (AuNPs) were coupled via thiol‐ene click chemistry. Significantly reduced electrical resistivity indicated sufficient loading density of AuNPs on such fiber surfaces. Then, Janus fibers were electrospun in a side‐by‐side arrangement, with “non‐functional” eADF4(C16) on the one and “functional” ntag(Cys)eADF4(κ16) on the other side. Post‐treatment was established to render silk fibers insoluble in water. Subsequent AuNP binding was highly selective on the ntag(Cys)eADF4(κ16) side demonstrating the potential of such silk‐based systems to realize complex bifunctional structures with spatial resolutions in the nano scale.