Biomedical Engineering Reference
In-Depth Information
instrumentation in total vertebrectomy eliminated the use of an anterior plate,
thereby reducing the time required for reconstruction of the anterior column and
eliminating surgical procedures in the segmental vascular structures. Further-
more, the prosthesis allowed for easy evaluation of bone formation within and
around the implant plus early diagnosis of any local recurrence.
213
To safely and efficiently monitor, diagnose, and stimulate tissue repair neu-
ral prosthesis for damaged brain or spinal cord, neural tissue repair requires an
implanted electrode of small size and excellent electrical conductivity.
50
But,
dense glial scar tissue formation on conventional metal silicon and metal alloy
neural implants frequently occurs that reduces the efficiency of electrical stimula-
tion and makes the probe useless during therapy. Nguyen-Vu and colleagues fabri-
cated a vertically aligned carbon nanofiber (VACNF) electrode array coated with
a thin film of electronic conductive polypyrrole polymers for neural implants.
214
The nanoelectrode array had more open and strong 3D structures with better
electrical conductivity that helped to form an intimate neural-electrical interface
between cells and nanofibers crucial for neural prosthesis. Two types of VACNF
electrode arrays with high aspect ratios and tested on neuronal cell (rat pheno-
chromocytoma, PC12 cells) differentiation showed that at discrete electrodes
after long-term cell cultures, the CNF arrays were responsive for the detection of
oxidized species generated by the cultured cells.
215
Initial studies suggested the
potential of resident CNFs for electroanalytical studies of neuronal cells indicat-
ing potential superiority over conventional metal electrodes. Thus, CNFs can be
used to design a neural probe with different conductivities at different parts of the
probe by controlling CNF weight percentages in polymer composites.
50
Transradial and transtibial prostheses can cost between US $6000 and $8000
while the transfemoral and transhumeral prosthetics cost between $10,000 and
$15,000 and as high as $35,000. The cost of an artificial limb does recur because
wear and tear require replacement every 3-4years. The socket must be replaced
within several months if it has issues and height may be an issue as well (http://
en.wikipedia.org/wiki/Prosthesis - cite_note-eight-36 and http://en.wikipedia.
org/wiki/Prosthesis - cite_note-eight-36 ).
6.5 TISSUE ENGINEERING
127
Conventionally, tissue engineering is the process where living cells and
biomolecules are incorporated into a scaffold that is placed into a bioreactor.
42
In vitro growth in the bioreactor allows engineered tissues to mature before they
are implanted. Ideally, cells grow and begin to form a tissue construct within
the scaffold. When the tissue construct is implanted into the body, the scaffold
continues to support further cell function, proliferation, and/or differentiation.
42
Furthermore, the scaffold allows blood vessels to infiltrate while it biodegrades.
Thus, tissue engineering requires three components: (1) a source of the cells,
(2) a suitable scaffold to engineer the specific type of tissue, and (3) a bioreactor
that resembles the body environment.
42
