STRATEGIES TO ENGINEER ELECTROSPUN SCAFFOLD ARCHITECTURE AND FUNCTION - Intelligent Scaffolds for Tissue Engineering and Regenerative Medicine - page 300

15.4.1 Processing Techniques for Tube- and Cord-Shaped
Structures
The production of tube-shaped scaffolds has been achieved
by two different electrospinning techniques. The first involves
electrospinning fibers around a cylindrical mandrel that is sub-
sequently removed. This simple technique—which has been
used to prepare scaffolds for vascular 49 and peripheral nerve
applications 50 —involvesminimalhandlinganddoesnotrequireany
subsequent processing. However, the electrospinning process may
be time intensive, as Li et al. 6 have reported that the achievement
of meshes of 1 mm in thickness can take several hours. Further, the
limited ability for cells to penetration into the resultant mesh (as
discussed in the previous section) can also beproblematic.
The second technique to produce a tube-shaped structure
involves electrospinning a thin flat mesh and then rolling it into a
tube. 51 , 52 This technique involves handling of the electrospun mesh
but has the potential to achieve thick electrospun meshes without
requiring several hours of electrospinning. Further, Hashi et al. 52
used this technique and seeded cells onto the electrospun mesh
prior to rolling in order to obtain a tubular vascular graft consist-
ing of multiple layers of electrospun fibers with cells distributed
throughout. In principle, this same technique could also be used to
produce three-dimensional grafts for connective tissues (e.g., ten-
don,ligament).
15.4.2 Variations on the Tube Structure for Blood Vessel
and Annulus Fibrosis Applications
In addition to simple tubes, researchers have sought to create more
complex architectures that better reflect the structure of blood ves-
sels. For example, Zhang and Chang describe the electrospinning
of fibers onto molds to create structures such as bifurcating blood
vessels. 53 Inaddition,theyshowedthatifpatternsofraiseddomains
are placed on the grounded target, then the deposition of fibers
is not purely random but includes preferential attachment at dis-
crete points. In addition, efforts have been made to create scaf-
folds for blood vessels with distinct luminal and adventitial layers