No abstract

Intervertebral disc (IVD) degeneration and accompanying lower back pain impose global medical and societal challenges, affecting over 600 million people worldwide. The IVD complex fibrocartilaginous structure is responsible for the spine biomechanical function. The nucleus pulposus (NP), composed of swellable glycosaminoglycan (GAG), transfers compressive loads to the surrounding fiber‐reinforced annulus fibrosus (AF) lamellae, which stretches under tension. Together, these substructures allow the IVD to withstand extremely high and complex loads. Key to mimic the complete disc must consider the properties of its substructures. This study presents three novel substructures–a biomimetic silk‐reinforced composite lamella for the AF, a GAG analog for the NP, and a novel biomimetic combined AF‐NP construct. The biomimetic AF demonstrates nonlinear, hyperelastic, and anisotropic behavior similar to the native human AF, while the NP analog demonstrates mechanical behavior similar to the human NP. The synergized biomimetic AF‐NP demonstrates similar behavior to the unconfined NP, with significantly increased deformations indicating improved performance. Validation of the AF‐NP construct mechanics using a finite element model yields results compatible with native human IVD under various physiological loadings. The ability of our AF‐NP construct to mimic the native IVD offers a revolutionary concept for the potential development of a fully functional IVD.

Multiscale micro−nano fibrous structures are a cutting-edge research area in material science and have drawn the attention of scientists in recent years. These structures are widely distributed in nature's materials and hold fascinating and unique properties, such as mechanical behaviors, high surface area to volume ratio, and special multiscale biological functionalities. Herein, we demonstrate step-by-step biomimetics of a multiscale composite material system and the influence of the different structural mechanisms on mechanical behavior. This is done using systematic biomimetics and investigation of the mechanical effect of every constituent. We have fabricated and characterized mechanically and structurally different material systems to get a comprehensive understanding of the structure−function relationship in multiscale biomimetic constructs (MSBCs) and examine the influence of the material selection and structure. We first characterized the electrospun nanofibers made of polyamide 6 (PA6) and gelatin-polyamide 6 (GPA6) and then constructed and characterized the combined constructs. Our micro−nano fibrous structures were constructed from combined unique coral collagen microfibers and PA6 and GPA6 nanofibers. These hierarchical structures demonstrated an entangled network of nanobridges among the micro collagen fibers. However, the GPA6-collagen structures showed better connectivity with the microfibers and were significantly stiffer and stronger than the PA6-collagen structures due to the material compatibility. Furthermore, our structures demonstrated a considerable resemblance with soft tissue structures. We embedded the MSBC in alginate hydrogel to form biocomposites that displayed a hyperelastic nonlinear behavior with significantly improved toughness and a remarkable similarity to the mechanical behavior of native soft tissues. Our results present great potential to be further developed as tailor-designed multiscale next-generation specialized structures for soft tissue repair and replacement.