Neuronal dynamics on patterned substrates measured by fluorescence microscopy
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esearch Letter
Neuronal dynamics on patterned substrates measured by fluorescence microscopy Joao Marcos Vensi Basso, Marc Simon, and Cristian Staii, Department of Physics and Astronomy, Tufts University, 574 Boston Avenue, Medford, MA 02155, USA Address all correspondence to Cristian Staii at [email protected] (Received 12 February 2018; accepted 26 March 2018)
Abstract Geometrical features are known to be very important in neuronal growth and the formation of neuronal networks. We present an experimental and theoretical investigation of axonal growth and dynamics for neurons cultured on patterned polydimethylsiloxane surfaces. We utilize fluorescence microscopy to image the axonal dynamics and show that these substrates impart a strong directional bias to neuronal growth. We model axonal dynamics using a general stochastic model and use this framework to extract key dynamical parameters. These results provide novel insight into how geometrical cues influence neuronal growth and represent important advances toward bioengineering neuronal growth platforms.
Introduction A single cortical neuronal cell extends two types of processes during growth: a long axon and several smaller dendrites. Once the neuron network is formed, the axon sends information to other neurons, while the dendrites receive electrical signals from other axons. To form the network, the axons extend (grow) through a complex environment. The tip of the axon (called the growth cone) is sensitive to a multitude of stimuli: biochemical, mechanical, and geometrical.[1,2] Much of what is currently known about the processes that direct the growth of axons in response to mechanical and geometrical cues comes from studies of neuron growth on patterned surfaces.[1–10] Directing axonal growth is also of great importance for bioengineering artificial neural tissue. Therefore, many studies focus both on understanding the biophysical mechanisms that control neuron growth, and on developing biocompatible surfaces for stimulating neuronal regeneration. For example, previous studies have shown the alignment of axonal growth on a variety of surfaces, including surface-bound proteins,[4–6] signaling molecules,[7] and topographical structures (ridges, indentations, and periodical patterns).[8–10] In our previous work,[9,10] we have demonstrated axonal alignment toward a single dominant direction on surfaces with engineered ratchet-like topography (asymmetric tilted nanorod or nano-ppx surfaces). These surfaces have been formed through vapor-phase polymerization and directed deposition of poly(chloro-p-xylylene) as described in Refs 9 and 10. The evaporation procedure generates a thin film of tilted nanorods that cluster together to form a periodic surface with a ratchet structure.[10] The geometrical and mechanical properties of these surfaces are comparable to the corresponding
properties of the polydimethylsiloxane (PDMS) surfaces used in this study. In our previous work, we have used a theoretical model based on the Fokker–Planck (FP) equation to quantify the angula
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