Polymer Nanopillars Induce Increased Paxillin Adhesion Assembly and Promote Axon Growth in Primary Cortical Neurons

Abstract

The complexity of the extracellular matrix consists of micro‐ and nanoscale structures that influence neuronal development through contact guidance. Substrates with defined topographic cues mimic the complex extracellular environment and can improve the interface between cells and biomedical devices as well as potentially serve as tissue engineering scaffolds. This study investigates axon development and growth of primary cortical neurons on OrmoComp nanopillars of various dimensions. Neuronal somas and neurites form adhesions and F‐actin accumulations around the pillars indicating a close contact to the topography. In addition, higher pillars (400 nm) confine the growing neurites, resulting in greater neurite alignment to the topographical pattern compared to lower pillars (100 nm). A comprehensive analysis of growth cone dynamics during axon development shows that nanopillars induce earlier axon establishment and change the periodicity of growth cone dynamics by promoting elongation. This results in longer axons compared to the flat substrate. Finally, the increase in surface area available for growth cone coupling provided by nanopillar sidewalls is correlated with increased assembly of paxillin‐rich point contact adhesions and a reduction in actin retrograde flow rates allowing for accelerated and persistent neurite outgrowth.

High Aspect Ratio and Light-Sensitive Micropillars Based on a Semiconducting Polymer Optically Regulate Neuronal Growth

“…Actin cytoskeleton is involved in many cellular behaviors and was shown to be significantly affected by surface topography. , We observed F-actin accumulations in the soma visible as rings around the micropillars (Figure a). Similar structures were observed around 3D nanostructures , and were associated with enabling pillar engulfment, thereby mediating the mechanical contact of the membrane to the pillar. , Moreover, F-actin accumulations around nanopillars above 400 nm in diameter were also associated with the increased membrane area at nanopillar locations, while on smaller nanopillars, F-actin accumulations were associated with high membrane curvature . Time-lapse imaging of Lifeact-RFP-expressing neurons showed that these structures are relatively stable due to the increased membrane area since curvature-dependent F-actin accumulations are highly dynamic structures (Figure a) .…”

“…68,69 We observed F-actin accumulations in the soma visible as rings around the micropillars (Figure 5a). Similar structures were observed around 3D nanostructures 32,70 and were associated with enabling pillar engulfment, 50 thereby mediating the mechanical contact of the membrane to the pillar. 71,72 Moreover, F-actin accumulations around nanopillars above 400 nm in diameter were also associated with the increased membrane area at nanopillar locations, while on smaller nanopillars, F-actin accumulations were associated with high membrane curvature.…”

“…18,30 By taking advantage of the excellent adaptability of the push-coating to different polymers, we extended this approach to fabricating micropillar arrays made of a hybrid organic/ceramic polymer, OrmoComp. OrmoComp is a commercial polymer with proven biocompatibility 31,32 that lacks optoelectronic properties. The push-coating technique was employed to fabricate micropillars with identical geometrical characteristics to those on P3HT arrays.…”

UV Laser‐Induced Carbon Microelectrode Arrays for Neuronal Recordings

“…[ 94 , 95 ] For primary neurons, it has been shown that nanostructured surfaces can enhance neurite branching. [ 96 , 97 ] Figure 4a,b shows the preferred neurite branching toward the rough carbon coating of the electrode active sites. The array of carbon electrodes can be identified on the sample surface by observing the increased aggregation of neurons and neurite branches.…”

Deciphering the Influence of Effective Shear Modulus on Neuronal Network Directionality and Growth Cones’ Morphology via Laser‐Assisted 3D‐Printed Nanostructured Arrays

“…[ 51 ] Due to the late time point at which the cells were fixed, it was not possible to assess the morphology of growth cones on the pillars. This is due to the high cell density and because axons are capable of progressing at a relatively high speed (8 µm h −1 ) [ 52 ] surpassing the total area of the pillar and propagating to the glass substrate.…”