Each year, approximately 2.2 million bone graft procedures are performed worldwide [1]. While bone autografts have been the gold standard of treatment for decades, autografts are associated with infection, sensory loss, hematoma, and longer hospital stays [2]. For these reasons, the use of synthetic bone substitutes is on the rise as a promising alternative for facilitating bone healing after injury. To design scaffolds that more closely match the mechanical and osteogenic behavior of natural bone, inspiration can be taken from bone's composite nanostructure. This complex hard tissue is comprised primarily of type I collagen, with carbonated hydroxyapatite (HAP) forming within collagen gap zones, creating an intricate nanoscale interaction between collagen and mineral. However, it is challenging to achieve good control over the location and orientation of the organic and inorganic components, as well as molecular scale integration of the two which can enhance the stability and mechanical properties of the composite. In order to address this challenge, we have designed hierarchical polyelectrolyte fibers to use as a template for polymer crystallization and directed mineral formation. We use a variety of electrospun polymer architectures to create nanofiber shish-kebabs (NFSKs) composed of a polymer fiber "shish" with polymers crystallized onto the surface in a repeating "kebab" structure [3]. The fiber scaffold lends tensile strength to the material, mimics the morphology and porosity of the extracellular matrix, and can direct the oriented formation of minerals. Using SEM, TEM, and DSC analysis, we can characterize the structure and phase behavior of the polymer fibers and NFSKs. Scattering and TGA determine the crystallinity and polymorph of mineral, as well as the mineral content that can be achieved when the fibers are mineralized in simulated body fluid. These materials are a versatile platform to study mineral formation, with the advantage of being both structurally and chemically tunable for nanoscale control over the formation of minerals on fibers. Additionally, the use of cheap, easily available synthetic polymers offers the opportunity for an easily replicated, scalable future bone scaffold material.
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