Biomedical Engineering Reference
In-Depth Information
with the electric field. When the applied electric field is strong
enoughtoovercomethesurfacetension,atinyjetisejectedfromthe
surface of the droplet and drawn toward the collecting plate. Dur-
ingthejetpropagationtowardthecollectingplate,thesolventinthe
jet stream gradually evaporates. The resulting product consists of a
nonwovenfibrousscaffoldwithalargesurface-area-to-volumeratio
and a small pore size (in microns).
4
The electrospun fiber proper-
ties and morphology depend on many parameters, such as solution
parameters(viscosity,surfacetension,conductivity,etc.),processing
conditions (voltage, feed rate, temperature, etc.), and ambient para-
meters (humidity, type of atmosphere, pressure, etc.).
13.3 Nanocomposite Preparation
Polymer nanofibers are chemically inert and do not have specific
functions. So biomolecules or biocompitable materials need to be
addedtothesurfaceofelectrospunnanofibersforuseinbiomedical
orotherpurposes.Biomoleculescanbeaddedtonanofibersthrough
surface modification/coating by means of several methods, such as
blending or physical coating, graft copolymerization via irradiation
(
-rays, electron beams, UV rays, etc.), plasma treatment, ozone or
H
2
O
2
oxidation, Ce
4
+
oxidation, etc. However, the blending method
is the most effective in making PHBV/proteins composites that are
useful for biomedicalpurposes.
γ
13.3.1
Principle of the Blending Method
Polymers are first dissolved with a suitable solvent. Biomolecules,
such as gelatin, keratin, and collagen, or biocompatable inorganic
materials, such as hydroxyapatite, silver, etc., are then mixed homo-
geneously with the polymer solution. The resultant solution is
then subjected to electrospinning in order to prepare nanocompos-
ites. Compared with synthetic polymers (i.e., PLA, PGA, PLGA, PCL,
PHBV, etc.), natural biopolymers (i.e., collagen, gelatin, keratin, silk,
fibrinogen, elastin, etc.) have good biocompatibility. However, the
processability of natural biopolymers is, in general, fairly poor.
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