Page 124 - Tailoring Electrospinning Techniques for Regenerative Medicine - Marc Simonet

CHAPTER 6
properties and introduction of bioactive cues into the material.18,19 Both PCL and PCL2kU4Un were characterized in-vitro before and a er sterilization to take into account that sterilization of synthetic materials may change their properties.16,20 The most promising valve was implanted as pulmonary valve replacement (n=10) to investigate initial functionality, cellular ingrowth with subsequent collagen formation and degradation of the synthetic polymer.
6.3 Materials and methods
6.3.1 Sca old production and characterization
Valve production and sterilization
All sca olds were electrospun in an EC-CLI climate- controlled electrospinning cabinet (IME Technology, Geldrop, NL) equipped with a 14G nozzle and a distance of 15 cm between nozzle and the target drum (29×100 mm) rotating at 100 rpm. Medical grade poly(ε-caprolactone) (Purasorb PC12 Gorinchem, The Netherlands) was dissolved in chloroform (purris p.a. stabilized with amylene, Sigma Aldrich) to a 20% (w/w) concentration, spun for 60 min at 23°C and 50% relative humidity at a flow rate of 25 μl/ min and a voltage of 16 kV. PCL2kU4Un (SyMO-Chem B.V. Eindhoven, The Netherlands) was dissolved in a mixture of chloroform and methanol (1% (w/w) of methanol) to a 12.5% (w/w) concentration, spun for 200 min at 23°C and 30% relative humidity at a
flow rate of 25 μl/min and a voltage of 14 kV. A coaxial jacket of chloroform-saturated air prevented the nozzle exit from clogging by suppressing excessive solvent evaporation.21 A er spinning, the electrospun sca olds were dried overnight under vacuum at room temperature to remove residual solvents.
The electrospun PCL and PCL2kU4Un valves were shaped out of a 40*29 mm electrospun tube adapting the style of a Carpentier-Edwards PERIMOUNT Aortic Heart Valve (Edwards Lifesciences Corporation, USA). For in-vitro testing, the tubes were sutured into shape in a 30 mm wide nitinol stent and using a stainless steel reinforcement ring on the inside to support the structure.
The electrospun samples and electrospun heart valve sca olds were sterilized by gamma irradiation (Synergy Health Ede, Netherlands) at a minimum dose of 25 kGy up to a maximum of 33 kGy.
Structural and intrinsic properties of the valve scaf- folds
Electrospun sca olds were characterized using scanning electron microscopy (SEM; Inspect F, FEI, Eindhoven, The Netherlands) at a voltage of 1 kV. The fiber diameters of electrospun PCL (sterile and non-sterile) and electrospun PCL2kU4Un, (sterile and non-sterile) were determined from scanning electron micrographs, measuring a minimum of 20 fibers each.
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