Distance Dependence of Neuronal Growth on Nanopatterned Gold Surfaces

Abstract

Understanding network development in the brain is of tremendous fundamental importance, but it is immensely challenging because of the complexity of both its architecture and function. The mechanisms of axonal navigation to target regions and the specific interactions with guidance factors such as membrane-bound proteins, chemical gradients, mechanical guidance cues, etc., are largely unknown. A current limitation for the study of neural network formation is the ability to control precisely the connectivity of small groups of neurons. A first step in designing such networks is to understand the "rules" central nervous system (CNS) neurons use to form functional connections with one another. Here we begin to delineate novel rules for growth and connectivity of small numbers of neurons patterned on Au substrates in simplified geometries. These studies yield new insights into the mechanisms determining the organizational features present in intact systems. We use a previously reported atomic force microscopy (AFM) nanolithography method to control precisely the location and growth of neurons on these surfaces. By examining a series of systems with different geometrical parameters, we quantitatively and systematically analyze how neuronal growth depends on these parameters.

Atomic force microscopy and its contribution to understanding the development of the nervous system

“…For example, growth promoting molecules can be patterned on different substrates via AFM nanolithography ('nanoshaving') [57,58]. Cantilevers can be attached to cells and cell-substrate [59] and cell-cell adhesion forces directly measured [60].…”

Neuronal growth as diffusion in an effective potential

“…Therefore, an alternative approach [3,4] is often used to uncover the basic rules that underlie the formation of functional neuronal connections. Within this approach one aims to create a simplified neuronal growth environment in vitro and to systematically investigate the effect that various cues: chemotactic, biochemical, mechanical, and topographical, have on the formation of neuronal networks.…”

Controlling neuronal growth and connectivity via directed self-assembly of proteins

“…Proper function of the nervous system ultimately relies on the formation and sustaining of these synapses throughout the body. As such, understanding the nature of axonal growth and synapse formation is currently an area of intense scientific research [6][7][8][9][10]. In time, this deeper understanding of growth processes may provide the groundwork for future medical procedures that provide nerve repair for individuals who have sustained head or spinal injuries [6,10].…”

“…As such, PDL coated surfaces provide a 2D environment on which neurons can naturally grow and form connections. Previous work has shown that PDL may be patterned in substrates otherwise inhospitable for neuron growth in order to direct neuron placement and growth [7,8]. Here, the alkanethiol SAMs prevent neuron growth anywhere on Au samples where PDL has not been deliberately patterned.…”