Biomedical Engineering Reference
In-Depth Information
The CNT-based composite was prepared by in situ polymerisation of acrylic
acid onto oxidised CNTs. The neuron differentiation eficiency on poly(acrylic
acid)-grafted CNT (PAA-g-CNT) thin films was compared with that of thin ilms
composed of poly(acrylic acid) (PAA) or PLO. The PAA-g-CNT thin ilms showed
enhanced neuron differentiation while maintaining cell viability, as assessed
by measuring the metabolic activity of dehydrogenases. SEM images showed
that the differentiated neurons on PAA-g-CNT surfaces have more branches,
suggesting that they are more mature. In addition, the CNT-based surface
exhibited a higher cell adhesion and protein (laminin) adsorption. Laminin
is a glycoprotein found in the extracellular matrix, the sheets of protein that
form the substrate of all internal organs (i.e., basement membrane). Laminin
has been reported to favour neuronal growth. 28 Indeed, laminin is a substrate
along which nerve axons can grow both in vivo and in vitro .
Thus, this work shows for the irst time that CNT-based polymer thin ilms
promote the differentiation of hESCs towards neuronal lineage.
The growth of somatosensory neurons on functionalised CNT mats was
recently reported by Xie et al. 29 MWNTs were functionalised by oxidation
using a mixture of sulphuric acid and nitric acid. The CNT mat was then
deposited on a track-etch membrane. The CNT substrate was found to be
a permissive substrate for the growth of somatosensory neurons from a
dorsal root ganglion. Neurite outgrowth and branching were observed by
SEM, as well as intertwinement between the neurites and the underlying
functionalised CNTs, indicating a strong interaction between both entities
at the nanoscale. No obvious neurite growth was observed on neurons
plated on a blank polycarbonate membrane. The authors suggested that
functional groups on the nanotube surface could act as anchoring seeds
which may enhance the adhesion of neurites on the CNT-based substrate.
This is consistent with previous studies, such as those reported by Haddon
and coworkers, that emphasise the positive impact of the functionalisation of
CNTs on permissivity for neuronal attachment and neurite outgrowth. 11,14,15
Neurons adhere to substrates via extracellular proteins such as laminin,
whose size is about 70 nm. 30 The authors pointed out that the analogous
dimension of CNTs and the roughness of the nanotube surface favour contact
with neurites by promoting better adhesion.
Wick et al. recently investigated the effects of SWNTs with different degrees
of agglomeration on primary cells of the nervous system (mixed neuroglial
cultures derived from the chicken embryonic spinal cord [SPC] of the central
nervous system or dorsal root ganglia [DRG] of the peripheral nervous
system). 31 The cells were exposed to SWNT agglomerates of submicrometre
sizes (SWNT-a) and to SWNT bundles (SWNT-b) composed of 10 to 20 tubes.
Suspensions of SWNTs-a and SWNTs-b affect glial cells from both tissue
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