Fracture behavior of multilayer fibrous scaffolds featuring microstructural gradients

Multilayer nanofibrous scaffolds that mimic the microstructure gradient of connective tissues have shown promising results in tissue regeneration, but the effect of these gradients on the mechanical performance of fiber meshes is poorly understood. In this study, trilayer nanofibrous gelatin scaffolds with gradually increasing fiber diameters (227–679 nm) and pore sizes (1.14–4.93 μm²) were fabricated using a sequential electrospinning process, producing a fiber density gradient over the scaffold thickness. The mechanical properties of the fibrous scaffolds were evaluated using uniaxial tensile and fracture tests. Deformation of microscopic crack tip openings was simulated using finite element analysis. Results from uniaxial and fracture tensile tests showed that the mechanical properties of fibrous scaffolds were governed by network architectures. The microstructure gradient yielded corresponding changes of material properties over the scaffold thickness. Simulation results showed different stress distribution and energy dissipation at each layer of the graded scaffolds. Finite element analysis also revealed that a combination of network density and alignment gradients can improve fracture toughness of graded scaffolds. This study provides guidelines and methodologies for designing tailored gradient fibrous scaffolds to more closely mimic the structural and mechanical properties of native interfacial tissues.