Highlighting strain rate dependent vibrational behavior of electrospun bundles for tendon/ligament and enthesis fascicle tissue regeneration

Enthesis tissue engineering aims to develop scaffolds that replicate the mechanical and structural gradients of the tendon/ligament-bone interface. Among biofabrication techniques, electrospinning is one of the most promising to fabricate morpho-mechanically relevant enthesis fascicle-inspired scaffolds. An unexplored characteristic of these nanofibrous scaffolds is their ability, when mechanically tested, to produce/transmit strain rate and nanofiber-fracture dependent mechanical vibrations, which can potentially influence surrounding tissues and cells. This study develops a method to investigate how scaffold geometry and material affect vibrational behavior under mechanical stimulation. Electrospun bundles of poly(L-lactic) acid/collagen type I (PLLA/Coll) were fabricated to mimic the fibrocartilage, enthesis junction, and tendon/ligament regions, while block copolymer poly(ethylene oxide terephthalate)-poly(butylene terephthalate) (PEOT-PBT) bundles represented only the tendon/ligament. Scaffolds were morphologically and mechanically characterized, including strain rate-dependent vibrational response and local mechanical properties via AFM nanoindentation. Scanning electron microscopy confirmed distinct fiber architectures. Under monotonic tensile tests, scaffolds exhibited strain rate-dependent mechanical behavior, PLLA/Coll bundles showed dominant vibrational frequencies up to 4.2 ± 0.9 Hz in a geometry-dependent manner, while PEOT-PBT scaffolds displayed higher vibration attenuation, with dominant frequencies peaking at 0.539 ± 0.063 Hz and lower tensile properties. Nanoindentation revealed spatial gradients in elastic modulus and energy dissipation across PLLA/Coll bundles, supporting a local mechanical decoupling at the enthesis-inspired junction. Integrating vibrational characterization with multiscale mechanical analysis provides a framework for designing scaffolds that more accurately reproduce the gradient mechanical environment of fibrous musculoskeletal tissues. These findings highlight the potential of this combined approach to improve the mechanical comprehension of electrospun scaffolds.