Sorption bands of the urethane groups had been observed in the PU ATR-FTIR spectrum (figure 1); moreover, the common absorption band of unreacted diisocyanate (at 2200 cm21) was not detectable, confirming full conversion in the monomers.(a)(b)rsfs.royalsocietypublishing.org200 mm100 mmInterface Concentrate four:Figure eight. (a) FEG-SEM micrograph of a PU scaffold obtained by melt-extrusion AM; (b) higher magnification detail of the trabecular arrangement. Table three. Stress at ten deformation (s10 ), residual deformation (1r) and power loss for cycles calculated from uniaxial cyclic tensile tests performed on bi-layered PU scaffolds. Values have been calculated employing the nominal dimensions of specimens. cycle4 bi-layered scaffoldstress (MPa)s10 (MPa)0.2-Aminoimidazole Formula 79 0.77 0.76 0.75 0.1r ( )two.5 two.7 2.9 3.0 three.energy loss ( ) 45.six 20.7 18.1 16.8 16.2 31 two three 4 5 strain (mm mm?) six 7Figure 9. Stress?strain behaviour throughout uniaxial tensile test (load cell: 10 N; strain price: 0.8 min21).under the processing conditions. A time sweep test was also carried out at 1658C under air as a tool to analyse PU thermomechanical stability below shear stresses. G0 and G00 did not modify as a function of time (figure 4) along with the molecular weight with the tested samples didn’t significantly reduce compared with all the synthesized PU (table 1), suggesting the possibility to melt procedure PU at 1658C without the occurrence of significant degradation phenomena. Finally, a frequency sweep test carried out at 1658C evidenced a pseudoplastic behaviour for the viscous polymer melt (figure 3), that is fundamental for melt extrusion of a high molecular weight polymer. On the basis from the performed characterization, PU was melt processed at 1558C without having the occurrence of thermomechanical degradation events. The melt-extrusion AM technique enables the preparation of scaffolds with controlled and reproducible geometry. A melt processing temperature of 1558C was located to become optimal for the fabrication of bi-layered scaffolds with a 08/908 lay-down pattern (figure eight). Because of the polymer’s high viscosity and rapid solidification rate, each and every extruded layer retained its shape, leading to a constant three-dimensional structure with desired pore size and fully interconnected pore volume. To the authors’ understanding, melt-extrusion methods have never ever been applied for the preparation of myocardial scaffolds.Price of 3-Hydroxy-1-methylazetidine A equivalent AM approach, pressure-assisted micro-syringe (PAM), has been previously proposed for the fabrication of scaffolds for myocardial regeneration, determined by the extrusion of polymer viscous options in a volatile solvent [23?5].PMID:24605203 However, the melt-extrusion AM approach has many advantagesover PAM: (i) it avoids the use of an organic solvent; (ii) melt viscosity is presumably larger than remedy viscosity, enabling the preparation of scaffolds which closely reproduce the computer-designed architecture; and (iii) owing towards the higher viscosity in the melt, melt-extrusion AM will not call for the use of a second polymer for layer-by-layer deposition of three-dimensional scaffolds. In analogy for the PAM approach, the optimization of scaffold design and style fabricated by melt-extrusion AM can cause anisotropic mechanical properties and topological cues suitable for CPC differentiation [23]. Within this preliminary work, scaffolds have been prepared with isotropic geometrical properties. Regardless of the standing debate on the optimal scaffold style within the field of cardiac TE, the geometry with the fabricated scaffol.
