Nanoscale Components of Neurons: From Biomolecules to Nanodevices

Neurons contain many structurally diverse nanoscale components, which individually carry out a well–defined function, or as is increasingly found to be the case, multiple functions. Nanoscale proteins are organized as systems. The neuronal membrane – embedded with multiple ion channels and receptors connected to scaffolding and effector proteins – represents a key information processing system in the neuron. In addition to receptors that mediate electrophysiological responses, there exist distinct membrane receptor populations that respond to neurotrophins and play critical roles in neural growth during development and in neural plasticity during adulthood. Despite their being touted as the main neuronal information processing system, membrane – embedded receptor systems operate relatively slowly, on the order of milliseconds to seconds. This has led researchers to probe other neuronal components in search of faster information processing speeds. DNA strands, which are well known to be the physical substrate of genes, act as semi–conductive wires when isolated outside the cell and are capable of transmitting and processing information analogously to the way a computer circuit might. Yet there is no evidence that DNA strands act as anything other than genes

in situ

. Cytoskeletal proteins form long strands that fill the entire interiors of neurons. Cytoskeletal proteins include neurofilaments, actin filaments, and microtubules. Traditional roles for the cytoskeletal proteins are mediating cell division, providing cell structure, and serving as a matrix for intracellular transport. Like DNA, microtubules are semiconductive and may transmit and process information, not only when isolated outside the cell, but also

in situ

. Nanotechnology provides new methods to investigate individual neuronal compartments and to manufacture small products ranging from mimetic molecules that interact with receptors to neural prosthetics that restore function following neural degeneration. Both recent breakthroughs and challenges relevant to creating effective interfaces between neurons and nanodevices are outlined.