End-functional PLLA nanofibers were fabricated into mats of random or aligned fibers and functionalized post-spinning using metal-free “click chemistry” with the peptide Tyr-Ile-Gly-Ser-Arg (YIGSR). Fibers that were both aligned and functionalized with YIGSR were found to significantly increase the fraction of mouse embryonic stem cells (mESC) expressing neuron-specific class III beta-tubulin(TUJ1), the level of neurite extension and gene expression for neural markers compared to mESC cultured on random fiber mats and unfunctionalized matrices. Precise functionalization of degradable polymers with bioactive peptides created translationally-relevant materials that capitalize on the advantages of both synthetic and natural systems, while mitigating the classic limitations of each. The use of 4-dibenzocyclooctynol (DIBO) as a functional initiator of poly-l-lactide (PLLA), a common polymer in medical applications, allows for the post-fabrication functionalization of the PLLA fibers as a “universal substrate”.