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 the different biofabrication techniques, electrospinning is surely one of the most promising to fabricate morpho-mechanically relevant enthesis fascicle-inspired scaffolds. An interesting and totally 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, the enthesis junction, and the 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. Scanning electron microscopy confirmed distinct fiber architectures. Under monotonic tensile tests to failure, scaffolds exhibited strain rate-dependent mechanical behavior, with PLLA/Coll bundles showing dominant vibrational frequencies up to 4.2 ± 0.9 Hz with a scaffolds’ geometry-dependent manner. PEOT-PBT scaffolds instead, displayed higher vibration attenuation, with dominant frequencies peaking at 0.539 ± 0.063 Hz. They also showed lower tensile properties, reflecting a different mechanical and vibrational profile respect to PLLA/Coll bundles. Integrating vibrational characterization with mechanical testing offers a novel framework for designing scaffolds that more accurately reproduce the gradient mechanical environment of fibrous musculoskeletal tissues such as tendons/ligaments and their entheses. These findings highlight the potential of this combined approach to further increase the mechanical comprehension of electrospun scaffolds. Graphical Abstract