Alignment of Cells and Extracellular Matrix Within Tissue-Engineered Substitutes - Advances in Biomaterials Science and Biomedical Applications - page 370

[34]. Magnetic circumferential alignment was performed prior gel compaction to produce
prealigned gels. When those gels were allowed to contract freely, the circumferential align‐
ment was lost, but when a mandrel was present, the alignment was better than with EMF
alone. This method can also be used to guide neurite outgrowth of neural cells. Dubey et al.
used collagen [81] and fibrin [82] aligned gel to control outgrowth of neurite. When fibers
were aligned, neurite outgrowths were stimulated and could therefore grow longer than
random aligned controls.
Retrospectively, this method is effective for biological scaffold such as collagen and fibrin,
but to our knowledge, alignment of synthetic materials such as poly(glycolic acid) (PGA) or
poly(D,L-lactide-co-glycolide) (PLGA) has not been performed yet. This technique requires
a special apparatus capable of generating a strong EMF. Cell viability does not seem to be
affected by EMF, allowing for a uniform cell distribution in the construct.
2.3. Electrospun nanofiber
Electrospinning of nanofibers is an interesting approach to produce scaffold for tissue engi‐
neering [83-89]. This technique can be used to produce aligned scaffold that will dictate cell
elongation by contact guidance [90]. The process of producing polymer microfiber using
electrostatic forces was patented in 1934 by Formhals [91] but tissue engineering applica‐
tions such as musculoskeletal [92] and vascular [93] has been developed recently. Electro‐
spinning can be performed with simple setup consisting of a syringe pump, a high voltage
source, and a rotating collector [85]. Precise description of the different possible setups and
techniques have been reviewed in details previously [94]. Briefly, a polymer solution is
hanging at the tip of a syringe needle by surface tension. When an electric current is applied,
EMF results in charge repulsion within the polymer solution, causing the initiation of a jet.
Solvent evaporate while jet is traveling, resulting in polymerisation into fibers, which are
captured by a collector [94]. Depending on settings and polymers used, those fibers can
range from 3 nm to greater than 5 μm in diameter [95]. This technique has been used to en‐
gineer many types of scaffolds for tissue engineering [90] including synthetic polymer such
as poly(D,L-lactide-co-glycolide) (PLGA) [96], poly-(ε-caprolactone) (PCL) [97], 50:50
poly(L-lactic acid-co-ε-caprolactone) (PLCL) fibers [98], or natural polymer such as collagen
[99] or fibrin [100] for various tissue applications. It is also possible to create composite scaf‐
folds by spinning different polymer solution either together or consecutively on the same
target. Due to the great plasticity of the technique, it is simple to engineer different patterns
to guide cell fate in the desired direction. In order to do so, a rotating mandrel can be used
to collect the fiber, resulting in aligned nanofibers [101].
Jose et al. [102] developed an aligned nanofibrous scaffold for bone tissue engineering. This
scaffold is a nanocomposite copolymer of PLGA and nano-hydroxyapatite (HA). Fiber di‐
ameters, glass transition temperature, storage modulus and degradation rate were charac‐
terized for different concentration of nano-HA from 0 to 20%. Briefly, average fiber
diameters were augmented from 300 nm for PLGA to 700 nm for 20% nano-HA but formed
aggregate at those high concentration. Fiber alignment capability was not influenced by
nano-HA concentration. Mechanical properties of the composite material were modulated