Page 81 - Tailoring Electrospinning Techniques for Regenerative Medicine - Marc Simonet

Sca old thickness was measured with a caliper a er drying o the ice crystals and residual solvents.
Mechanical properties
For each material the fiber sti ness (k) was estimated according to
(2)
with A being the cross-sectional area of the mean fiber diameter (deducted from SEM images), E the Young’s modulus of the bulk material (PLA 3.7 GPa, PCL 440 MPa) and L the fiber length (arbitrarily set to 1 m). We are aware that these sti ness values are only a first estimation and do not precisely reflect the more complex reality.39 These values were only used to compare the electrospun sca olds against each other, so the values in Table 4.1 should be used with caution.
The mechanical properties of all the electrospun sca olds groups spun on the 50 mm drum were measured on 5 strips at room temperature on a Zwick tensile tester (Model Z010, Germany) at a crosshead speed of 100 %/min and a sample gauge length of 10 mm. The Tangent modulus was measured at 2.5 % elongation from the obtained stress-strain curves. Tangent modulus was chosen over the more o en used young’s modulus, since the sca olds are not considered fully elastic. Yield strength was determined at the end of the linear stress strain
response and the ultimate tensile strength (UTS) was defined as the peak stress value. All mechanical curves for Figure 4.7 were averaged using the build- in function in Origin 8.5.1 (OriginLab Corporation, USA) and displayed up to the UTS.
4.3.4 Validating cell infiltration potential
Cell preparation and seeding
Vascular derived cells were harvested from the
human vena saphena magna, which was obtained
following the Dutch guidelines for secondary use
of materials. Cells were cultured in Dulbecco’s 4 modified Eagle’s medium (Invitrogen) supplemented
with 10% fetal bovine serum (Greiner Bio one), 1% GlutaMax (Invitrogen), 1% penicillin/streptomycin (Lonza). 5 PCL conventional and 5 PCL LTE spun sca olds with a fiber diameter of 0.9 μm were cut into strips of 25 x 5 mm and constrained onto stainless steel rings. Sca olds were sterilized in 70 % ethanol for 15 minutes and subsequently le to dry. A er 3 subsequent washes with phosphate bu ered saline (PBS; Sigma-Aldrich), sca olds were incubated in medium and placed in an incubator (37 °C, 5 % CO2) overnight to facilitate cell attachment. Before seeding, the medium was removed and the sca olds were aspirated. The cells were seeded at a cell density of 1.6 x 104 mm-3 by using fibrin as a cell carrier, as previously described40. A er seeding, the sca olds were maintained in the culture medium as described above, supplemented with L-ascorbic acid
TAILORING THE VOID SPACE AND MECHANICAL PROPERTIES IN ELECTROSPUN SCAFFOLDS
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