Biomedical Engineering Reference
In-Depth Information
important clinical goals, it also offers unique tools for challenging the main ideas of
modern neuroscience.
The issue of the interface between the electrode and the neuronal tissue has been
addressed by biomaterials and tissue-engineering approaches. It has been shown
that material texture or topographic features are crucial in promoting attachment
and growth of neurites in vitro, signifi cantly implementing stability of recordings
(Schwartz et al.
2006
). Indeed, efforts to improve implant design promote the devel-
opment of more reliable and long-term recordings. The observation that engineered
nanoscale features, obtained by layering nanotubes on a substrate surface, encour-
age neuronal growth while inhibiting astrocyte attachment (Moxon et al.
2004
)
hints at the idea of exploiting the technological aspects of nanomaterials to optimize
interfaces between a technical device and the neuronal environment.
Current developments of nanotechnology applications to biology and medicine
are strongly based on the capacity of nanomaterials to interact with biological sys-
tems at a subcellular level. The ability to chemically control nanosubstrates pro-
duces materials, which functionally integrate with cellular and physiological
systems to an extraordinary degree (Giugliano et al.
2008
). In particular, this latter
interaction can be understood and engineered with a high level of specifi city (Silva
2006
) . The fi eld of neuronal interfaces is particularly related to such an interdisci-
plinary approach, and the mastering of new conductive nanoparticles is paving the
way to a novel kind of neuroelectronics. Nanotechnology applications to the CNS
have the potential to provide a new paradigm for the design of advanced interfaces
and suggest the development of hybrid circuits that couple the strength of nanoelec-
tronics to biological computing components. One of the more attractive materials
employed to develop nano-bio hybrid systems is represented by carbon nanotubes
(CNTs). CNTs have been at the forefront of nanotechnology and can be manufac-
tured with a very broad range of thermal, electronic, and structural properties and
their surface modalities can be adapted very conveniently (Tasis et al.
2006
) . Due to
their outstanding features, CNTs have been quickly recognized as a technology
platform for biomedical applications (Sucapane et al.
2008
) .
In the context of extracellular electrodes, the exploration of nanotechnologies,
and specifi cally of CNT, captured a signifi cant momentum (Keefer et al.
2008
) . In
fact, although inadequate for accurate recording and stimulation access at the sub-
cellular level, extracellular electrodes fulfi ll other equally important prerequisite
for in vivo applications, including the penetration of mechanically tough connec-
tive tissue (e.g., the dura mater), access to neurons whose size is much smaller than
that of a glass pipette tip, need of developing chronic electrical stimulation and
recording without electrochemical cellular insults, as well as the growing demand
in designing electrodes with increased sensitivity without apparent loss in selectiv-
ity. Mechanical stability is particularly relevant not only in the context of acute
in vivo animal experiments, but also in cases, where chronic unrestrained experi-
mental animal preparations are used or during neurosurgical procedures. In addi-
tion, recording or stimulating electrical activity from accurately spaced CNS sites
in parallel, crucial for topographic functional analysis, avoid considering any alter-
native technique.
