Controlling neuronal growth and connectivity via directed self-assembly of proteins
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Controlling neuronal growth and connectivity via directed self-assembly of proteins Daniel Rizzo, Ross Beighley, James D. White and Cristian Staii Department of Physics and Astronomy, and Center for Nanoscopic Physics, Tufts University, 4 Colby Street, Medford, MA, 02155, U.S.A. ABSTRACT Materials that offer the ability to influence tissue regeneration are of vital importance to the field of Tissue Engineering. Because valid 3-dimensional scaffolds for nerve tissue are still in development, advances with 2-dimensional surfaces in vitro are necessary to provide a complete understanding of controlling regeneration. Here we present a method for controlling nerve cell growth on Au electrodes using Atomic Force Microscopy -aided protein assembly. After coating a gold surface in a self-assembling monolayer of alkanethiols, the Atomic Force Microscope tip can be used to remove regions of the self-assembling monolayer in order to produce well-defined patterns. If this process is then followed by submersion of the sample into a solution containing neuro-compatible proteins, they will self assemble on these exposed regions of gold, creating well-specified regions for promoted neuron growth. INTRODUCTION Atomic Force Microscope based Nanolithography Formation of self-assembling monolayers (SAMs) is an extensively studied and diversely applied chemical process [1-3]. When a metallic substrate such as Au(111) is present in a solution of alkanethiols, individual molecules covalently bond to the surface via the sulfur head group. If left for a sufficient period of time, alkanethiols assemble onto the Au(111) surface in a (¥3×¥3)R30° arrangement [3]. The close packed nature of this assembly causes the underlying Au surface to become chemically isolated from its environment. The Atomic Force Microscope (AFM) may then be used to both image the SAM-coated Au, and selectively remove regions of the SAM to create patterns of exposed Au. This process (called nanoshaving) may be followed by a subsequent assembly of molecules (alkanethiols, proteins, etc.) onto the then exposed Au patterns [4,5]. Neuron Growth Neurons have three main structural components: the cell body, axons, and dendrites. The latter two appear as finger-like projections from the cell body, which are referred to collectively as neurite processes. The axon is a much longer, thinner process that relays electrical signals to neighboring neurons, while the shorter, thicker dendrites receive them. The point at which one neuron’s axon forms a connection with a neighboring dendrite is known as a synapse. 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 [6-10]. 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].
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