(a) SEM showing nanofibers in E2 PA and BDNF PA gels. (b) Storage moduli of E2 PA and BDNF PA. (c-d) Scanning electron micrograph and (e) confocal micrograph images showing cortical neurons seeded on top of 3D PA scaffolds for 1 week in vitro. (f) Confocal images showing top and side (z-stack =160 μm) view sections of cells cultured on PA gel scaffolds for 1 week in vitro (images show cells stained with MAP-2 (dendritic marker, green), and Tuj-1 (neuronal marker, red). (g) Depth-coded z-stack reconstructions showing cell infiltration after 1 week in vitro. (h) Quantification of cell infiltration depth in E2 PA, BDNF + E2 PA, BDNF peptide + E2 PA, and BDNF PA gels. (i) Representative traces of action potentials elicited by 1 second, 10pA current injection steps from 10–80pA recorded from neurons in BDNF + E2 PA, BDNF PA and E2 PA gels, 1 week in vitro. (j) Plot of current injection versus number of spikes for conditions in (i). **P<0.01 and ****P<0.0001. LSD test (b and h) and ANOVA followed by posthoc analysis was used for current clamp recordings (j).