Hierarchical Characterization and Nanomechanical Assessment of Biomimetic Scaffolds Mimicking Lamellar Bone via Atomic Force Microscopy Cantilever-Based Nanoindentation

Brian Wingender; Yongliang Ni; Yifan Zhang; Curtis Taylor; Laurie Gower

doi:10.3390/ma11071257

Hierarchical Characterization and Nanomechanical Assessment of Biomimetic Scaffolds Mimicking Lamellar Bone via Atomic Force Microscopy Cantilever-Based Nanoindentation

Materials (Basel). 2018 Jul 22;11(7):1257. doi: 10.3390/ma11071257.

Authors

Brian Wingender¹, Yongliang Ni², Yifan Zhang³, Curtis Taylor⁴, Laurie Gower⁵

Affiliations

¹ Department of Biomedical Engineering, University of Connecticut Health Center, Farmington, CT 06030-165, USA. wingender@uchc.edu.
² Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, FL 32611, USA. niutouchaoren@ufl.edu.
³ Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, FL 32611, USA. yifanzhang97@ufl.edu.
⁴ Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, FL 32611, USA. curtis.taylor@ufl.edu.
⁵ Department of Materials Science and Engineering, University of Florida, Gainesville, FL 32611, USA. LGower@mse.ufl.edu.

Abstract

The hierarchical structure of bone and intrinsic material properties of its two primary constituents, carbonated apatite and fibrillar collagen, when being synergistically organized into an interpenetrating hard-soft composite, contribute to its excellent mechanical properties. Lamellar bone is the predominant structural motif in mammalian hard tissues; therefore, we believe the fabrication of a collagen/apatite composite with a hierarchical structure that emulates bone, consisting of a dense lamellar microstructure and a mineralized collagen fibril nanostructure, is an important first step toward the goal of regenerative bone tissue engineering. In this work, we exploit the liquid crystalline properties of collagen to fabricate dense matrices that assemble with cholesteric organization. The matrices were crosslinked via carbodiimide chemistry to improve mechanical properties, and are subsequently mineralized via the polymer-induced liquid-precursor (PILP) process to promote intrafibrillar mineralization. Neither the crosslinking procedure nor the mineralization affected the cholesteric collagen microstructures; notably, there was a positive trend toward higher stiffness with increasing crosslink density when measured by cantilever-based atomic force microscopy (AFM) nanoindentation. In the dry state, the average moduli of moderately (X51; 4.8 ± 4.3 GPa) and highly (X76; 7.8 ± 6.7 GPa) crosslinked PILP-mineralized liquid crystalline collagen (LCC) scaffolds were higher than the average modulus of bovine bone (5.5 ± 5.6 GPa).

Keywords: PILP; biomimetic mineralization; bone apatite; cantilever-based AFM nanoindentation; cholesteric; cholesteric collagen; intrafibrillar mineral; lamellar; liquid crystalline collagen.