Direct laser texturing of biomimetic surfaces for neural tissue engineering

The control of the outgrowth of neuronal cultured cells is of critical importance in a wide spectrum of neuroscience applications including tissue engineering scaffolds and neural electrodes. However, the study of neuron cell outgrowth on more complex topographies remains limited. Phenotype alteration of stem cells and differentiated neuronal cells cultured on traditional flat substrates that lack structural cues, emphasize the necessity to shift from 2D to 3D cell culture models. The aim of the present study was to investigate the cellular response to topographical cues both at the micro and the nanoscale. In particular, we have previously reported that the artificial surfaces obtained by direct femtosecond laser texturing of solid surfaces in reactive gas atmosphere exhibit roughness at both micro- and nano-scales that mimics the hierarchical morphology of natural surfaces [1]. Variation of the laser fluence, alters the surface morphology, while the respective patterned substrates exhibit different roughness ratios and wettabilities. Cells with nerve cell phenotype were cultured on the substrates. Results on the culture of PC12 cells showed that the morphology of microspiked surfaces alone can be used for directional cytoskeletal rearrangement and subsequent differentiation into a neuronal phenotype. Besides this, the experiments with DRG/SCG nerve cells showed a good attachment, outgrowth and network formation and depending on the substrate morphology there was a differential orientation of the cells. In particular, cells were randomly oriented on low roughness surfaces, whereas there was a trend for parallel alignment on the intermediate and high roughness substrates. Our results indicate a method to tune cell responses by proper selection of the surface free energy of the substrate and may be promising for the design of cell culture platforms with controlled differentiation environment.