Page 145 - Tailoring Electrospinning Techniques for Regenerative Medicine - Marc Simonet

Among the various sca old fabrication technologies, electrospinning holds the promise to be a key enabling technology for tissue engineering applications. This is largely the case because it enables the production of a continuous nano- and microfiber using an extensive range of natural and synthetic polymers. These fibers are processed in sca olds which automatically resemble some features of ECM. Until recently, a general lack of reproducibility, limited cell in-growth and small productivity rate formed key challenges reducing the success of this technology to prevail into a biomedical product. During the process of this thesis we focused on increasing the reproducibility and cell in-growth to increase the chances of success for this method in the field of regenerative medicine. Finally, we applied the findings into a sca old for in-situ heart valve regeneration. The main findings of this thesis are summarized below, followed by a discussion on their relevance and applicability in electrospun sca olds for tissue engineering.
7.1 Main findings
Having stable process parameters and a reproducible production outcome is crucial for any technique in order to prevail into an industrial setting, even more so for the demanding and heavily regulated medical sector. Due to its inherent variability, leading to inconsistencies within one batch as well as to batch
to batch variations, electrospinning was suggested to be rather an art than a science, even by people in the field.1 With, in the course of this thesis developed, climate controlled electrospinning equipment, we were able to show how important a tightly controlled environment around the electrospinning process is, in order to stabilize the process and to obtain reproducible sca old morphologies. In chapter 2 we proved that a variation of a few percent in relative humidity can already change fiber orientation and fiber morphology. We also showed that an interplay of relative humidity and water solubility of the solvent allows a tuning of di erent fiber surface structures.
In order to create a homogeneous tissue
engineered construct, it is essential that cells can
migrate and grow throughout the entire sca old.
Since electrospinning creates fully interconnected
porous structures, it seems to be a highly suitable
method to produce sca olds for tissue engineering. Conventional electrospinning inherently produces
the sca old fiber-layer by fiber-layer, so the size of
the fully interconnected pores scales (down) with
the fiber diameter. This hinders cell infiltration
and migration for sca olds consisting of fibers 7 with a few micrometer in diameter.2,3 In chapter 3,
we introduced a new method, low-temperature electrospinning (LTE), to vastly increase this space between the fiber layers. Using a cooled target resulted in a simultaneous collection of electrospun fibers and ice crystals from the surrounding humid
GENERAL DISCUSSION
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