Nano-Scale Surface Topology Improves Neuronal Development in Culture

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Neurons may be grown on opaque silicon surfaces covered with poly-L-lysine, the same way it is usually carried out on glass coverslips. Neuronal development may also be improved by structuring silicon surfaces with reactive ion etching. Here, we produced silicon samples by a classical photolithography process with an alternation of 1mm-wide bands, presenting atomically flat or rough topologies.Hippocampal neurons from E18.5 mice, grown over these samples, developed faster on rough bands: they differentiated an axon more readily after 2 days in culture (75% neurons display an axon vs 60% on flat surfaces) and their total neuritic length was 50% larger whereas they developed 20% less neurites. Moreover, neurons with neurites in both areas preferentially differentiated an axon onto the rough surface (76% polarized neurons).Finally, we characterized the topology of rough surfaces using Scanning Electron Microscopy. We observed 1µm-high silicon nano-peaks randomly distributed on the surface. Interestingly, our observations indicated that neurites grew on top of the nano-peaks with a typical distance between adhesion points of about 600nm.View Large Image | View Hi-Res Image | Download PowerPoint Slide Neuron on rough silicon surface (bar, 5 µm), and zoom over a neurite (dark rectangle and inset; bar, 500 nm).