Mesoscopically ordered and 3D printed nanocomposites inspired from the ligament-bone interface

Abstract

Event Abstract Back to Event Mesoscopically ordered and 3D printed nanocomposites inspired from the ligament-bone interface Anand Rajasekharan1, Romain Bordes1 and Martin Andersson1 1 Chalmers University of Technology, Chemistry and Chemical Engineering, Sweden Introduction: The insertion site between soft and hard tissues such as the bone-ligament interface is crucial for muscoskeletal function and is highly prone to injuries. The interface tissues have a complex variation in structure and chemical-biological composition[1]. Modern grafts that support such injured interfaces lack necessary mechanical fixation and regenerative capacity. An important factor required from synthetic grafts for such applications is to transfer and minimize stress concentrations at the insertion site. Natural interfaces achieve this with the help of a well-ordered structure and chemical heterogeneity[1]. In light of this, we have developed a mesoscopically ordered nanocomposite with a mineral gradient that might act as a graft plug at injured interfaces. The composite is inspired from the matrix heterogeneity of the ligament-bone interface in terms of mesostructural order, anisotropy and chemical composition. Methods: Inspired by the collagen organization in bone and ligament, we use lyotropic liquid crystalline (LC) gels possessing a mesoscopically ordered structure as the matrix[2]. To create a macroscopic, porous material, the plug was fabricated via traditional molds and 3D printing by combining two distinct LC inks (figure 1A and 1B). The LC combination was covalently photo-crosslinked to form resilient and flexible polymerized liquid crystal matrices (PLCs). Next, a compositional gradient of bone-like hydroxyapatite (HA) was formed in-situ within the aqueous domains of the part of the PLC possessing calcium and phosphate ions, yielding a 3D, composite material with a graded mineral content (figure 1A). Figure 1(A) A traditionally molded and (B) 3D printed, porous, heterogeneous nanocomposite with mineral gradient (C) SAXS scattering confirms presence of mesoscopic order and anisotropy in both the mineralized and non mineralized sections (D) SEM image shows differences in morphology between mineralized and non-mineralized sections of the composite (E) Elemental scan shows increasing calcium to carbon ratio along the length of the composite shown in figure 1D Results: Small angle X-ray scattering (SAXS) data of the nanocomposite confirms the presence of meso-ordered (hexagonal) structure with long-range anisotropy similar to bone (figure 1C). Moreover cross-sectional electron microscopy images of composites show a clear gradient of the HA nanoparticles along macroscopic length scales of the PLC matrix (figure 1D and 1E). We have also shown the possibility to fabricate these heterogeneous structures via 3D printing with a porous architecture, possibilities towards scaffolding a biological heterogeneity of cells. Current work focuses on studying the composites in-vitro with different cell lines to assess cell behaviour on the heterogeneous surfaces. Conclusion: In this work, we have developed a heterogeneous nanocomposite possessing a mesoscopically ordered structure and a controlled gradient in mineral density and mechanical stiffness, inspired by the well-ordered matrix heterogeneity observed in natural bone-ligament interfaces. Knut and Alice Wallenberg Foundation; MAX-lab (Lund, Sweden)