Trauma to the central and peripheral nervous systems often lead to serious morbidity. Current surgical methods for repairing or replacing such damage have limitations. Tissue engineering offers a potential alternative. Here we show that functionalized α-helical-peptide hydrogels can be used to induce attachment, migration, proliferation and differentiation of murine embryonic neural stem cells (NSCs). Specifically, compared with undecorated gels, those functionalized with Arg-Gly-Asp-Ser (RGDS) peptides increase the proliferative activity of NSCs; promote their directional migration; induce differentiation, with increased expression of microtubule-associated protein-2, and a low expression of glial fibrillary acidic protein; and lead to the formation of larger neurospheres. Electrophysiological measurements from NSCs grown in RGDS-decorated gels indicate developmental progress toward mature neuron-like behavior. Our data indicate that these functional peptide hydrogels may go some way toward overcoming the limitations of current approaches to nerve-tissue repair.

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Protein trans-splicing using split inteins is a powerful and convenient reaction to chemically modify recombinantly expressed proteins under mild conditions. In particular, semisynthetic protein trans-splicing with one intein fragment short enough to be accessible by solid-phase peptide synthesis can be used to transfer a short peptide segment with the desired synthetic moiety to the protein of interest. In this chapter, we provide detailed protocols for two such split intein systems. The M86 mutant of the Ssp DnaB intein and the MX1 mutant of the AceL-TerL intein are two highly engineered split inteins with very short N-terminal intein fragments of only 11 and 25 amino acids, respectively, and allow the efficient N-terminal labeling of proteins.