Microstructural manipulation of electrospun scaffolds for specific bending stiffness for heart valve tissue engineering

Abstract

Biodegradable thermoplastic elastomers are attractive for application in cardiovascular tissue construct development due to their amenability to a wide range of physical property tuning. For heart valve leaflets, while low flexural stiffness is a key design feature, control of this parameter has been largely neglected in the scaffold literature where electrospinning is being utilized. This study evaluated the effect of processing variables and secondary fiber populations on the microstructure, tensile and bending mechanics of electrospun biodegradable polyurethane scaffolds for heart valve tissue engineering. Scaffolds were fabricated from poly(ester urethane) urea (PEUU) and the deposition mandrel was translated at varying rates in order to modify fiber intersection density. Scaffolds were also fabricated in conjunction with secondary fiber populations designed either for mechanical reinforcement or to be selectively removed following fabrication. It was determined that increasing fiber intersection densities within PEUU scaffolds was associated with lower bending moduli. Further, constructs fabricated with stiff secondary fiber populations had higher bending moduli whereas constructs with secondary fiber populations which were selectively removed had noticeably lower bending moduli. Insights gained from this work will be directly applicable to the fabrication of soft tissue constructs, specifically in the development of cardiac valve tissue constructs.

From single fiber to macro-level mechanics: A structural finite-element model for elastomeric fibrous biomaterials

“…non-linearity, anisotropy and elastic moduli [35]) and of out-of-plane behavior (e.g. bending stiffness [36]). At smaller scales (mesoscopic scale with a characteristic length of ~100 μm), various model predictions [2-4, 9, 12, 25, 28] can estimate fibers network kinematics and mechanics [37] and elucidate the effects of macroscopic deformations and micro architecture on cells/inclusions.…”

Laminated collagen-fiber bio-composites for soft-tissue bio-mimetics

“…Mechanical properties of biomaterials can be tuned by adjusting diverse parameters, such as crosslinking [19], material concentration [20,21], and architecture [22,23]. The mechanical properties of fiber-reinforced bio-composites are relatively easier to manipulate by adjusting their fiber fraction and orientation.…”

Fibers for hearts: A critical review on electrospinning for cardiac tissue engineering

“…A comprehensive study of the same group of electrospun PEUU under variable conditions which modelled the effects of fiber orientation on the macro-mechanical properties of the scaffold, has shown that the high velocity electrospun scaffolds exhibited highly anisotropic mechanical properties closely resembling the native pulmonary heart valve leaflet [103]. Aiming to mimic the mechanical properties of a native pulmonary valve in both flexural and equi-biaxial tensile response, Amaroso et al studied the effect of microstructural features, that are important on the flexural behaviour of electrospun scaffolds, by introducing secondary electrospun fibers to the PEUU with simultaneous electrospinning [104]. It was noticed that mixed fiber constructs with higher modulus had higher bending and tensile moduli when secondary fibers were stiffer (PCL) than PEUU, whereas sacrificial fibers (PEO) within scaffolds were found to decrease overall construct modulus.…”