Page 11 - Tailoring Electrospinning Techniques for Regenerative Medicine - Marc Simonet

Tissue engineering enables the production of living tissue replacements. The sca old represents the basis for such a replacement, providing the appropriate environment for cells to produce their tissue. In order to fully unlock the potential of tissue engineering, it is crucial that the sca old mimics the native extracellular matrix (ECM) of the target tissue as closely as possible. This current paradigm in regenerative medicine is one of the reasons why electrospinning gained so much attention to produce sca olds for tissue engineering. Electrospinning enables numerous types of materials to be spun into di erent kinds of fibrous sca olds, which structurally resemble the native extracellular matrix. Many key biomimetic factors, such as the mechanical properties, the biocompatibility, and the biodegradation profile are related to the choice of the electrospinning material, but can also be adjusted by the electrospinning process itself. To instruct cells and guide tissue formation, bioresponsive or bioactive molecules can be included into electrospun sca olds. In this thesis, tools are presented to improve the reproducibility, functionality and applicability of electrospun sca olds for in-vivo and in-situ applications. All with the overall goal to underline and improve the suitability of electrospinning as a method to develop products for regenerative medicine/purposes.
Lack of reproducibility is one of the main challenges holding back the development of
electrospun medical products. Using a, over the course of this PhD developed, climate controlled electrospinning chamber vastly increases the reproducibility of the electrospinning process regarding process stability, fiber morphology and orientation. Moreover, it allows to use ambient parameters, such as relative humidity, to adjust sca old features like the fiber morphology.
Proper cell infiltration into the sca old is crucial to produce a homogeneous tissue. A drawback of conventional electrospun sca olds is the limited cell infiltration since the fibrous layers are densely packed on top of each other. This stops cell infiltration particularly when using fibers with a diameter smaller than a few micrometers. The first part of the thesis focuses on increasing and controlling the void space in electrospun sca olds by developing a process called low-temperature electrospinning (LTE). Cooling the electrospinning target to -35°C and below, allows the simultaneous deposition of polymer fibers and ice crystals from condensing humidity. These ice crystals are intimately embedded between the polymer fibers and serve as a pore template, increasing the voids and thereby facilitating cell ingrowth also for submicrometer fibrous sca olds. In line with the increase in void space, the tangent modulus of the sca olds shi s towards the range of native so tissues like blood vessels. While both the physiological mechanical properties and high porosity are promising for tissue
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