NANOTECHNOLOGY: A TOOLKIT FOR CELL BEHAVIOR - 3D Bioprinting and Nanotechnology in Tissue Engineering and Regenerative Medicine - page 3

FIGURE 1.1
Comparison of carbon nanotubes and carbon nanofibers showcasing their morphological differences, and relative
difference in diameter. Image is from Kim et al. (2013) .
Many researchers have also drawn upon the high electrical conductivity exhibited by CNTs to create
conductive scaffolds for neural tissue regeneration ( Gacem et al . , 2013 ). Improved peripheral nervous
system (PNS) ( Serrano et al . , 2014 ) and central nervous system (CNS) ( Kim et al . , 2014 ) regeneration
and stem cell performance ( Serrano et al . , 2014 ) have been observed when utilizing CNTs. In particu-
lar, a 3D porous scaffold was fabricated from chondroitin sulfate, a biomaterial constituent of native
nervous tissue, and MWCNTs via a freeze-drying method, coated with polylysine, and cultured with rat
embryonic neural progenitor cells. After 20 days of culture, a viable cell population of more neuron than
glial cells was observed, contrasting the 2D, CNT-less controls ( Serrano et al . , 2014 ). In another study,
MWCNTs were combined with collagen to create a collagen-CNT nanomaterial scaffold that acceler-
ated and directed differentiation of human decidua parieltalis stem cells into a neural lineage ( Sridharan
et al . , 2013 ). The nanocomposite scaffold elucidated a previously unknown differentiation pathway
of parieltalis cells, unique to this scaffold. In addition, CNTs can also be used to reveal important
mechanisms of neuronal activity. In this specific study, MWCNTs with a small number of walls, dubbed
“few-walled CNTs,” were used as a substrate to examine the chloride shift; a hallmark trait of neuronal
disorder and injury ( Liedtke et al . , 2013 ). Primary CNS neurons were found to have a highly accelerated
chloride shift and very high potassium chloride cotransporter 2 expression. The CNTs on the substrate
promoted this expression through interaction with voltage-gated sodium channels. In this manner, few-
walled CNTs can be employed to reduce chloride concentration and exchange between neurons.
CNTs continue to have great utility across many other tissue types. At first glance, the musculo-
skeletal system is very different from the cardiac and neuronal systems previously discussed; however,