Microscale investigation of composition and mechanics of cement lines in cortical bone as a function of age and health

• Applicant: Dr. Michael Wurmshuber
• Subject Area: Biomaterials
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 554757145

Bone mechanics research is largely motivated by age-related bone fragility and osteoporosis. Here we propose to investigate the cement line (CL) an understudied structural element providing an important toughening mechanism to bone Despite the important role of CLs surrounding osteons in healthy bone - they lead to crack deflection and twist - little is known about their compositional and (micro-)mechanical properties. As CL thinness (3-5 µm) makes them difficult to assess, we propose to perform (micro-)mechanical tests, compositional analysis and in vitro modifications to characterize them. With this research we will provide mechanistic insights into CL structure and function and hope to aid the long-term future goal of improving bone fracture prediction. The hypotheses are: 1) Micromechanical properties of cement lines (relative to their bone material surroundings), are correlated to the cement lines’ ability to dissipate energy, and therefore influence the toughening of cortical bone. A prediction of the toughening behavior of cortical bone from micromechanical properties of cement lines is possible. 2) Osteon age, donor age, medical condition and history have a direct and measurable influence on hardness, modulus, strength and deformation behavior of cement lines and hence, on the toughening of cortical bone. We will use well-characterized femoral neck samples of human origin (osteoporotic/healthy) from an earlier study and additional fresh samples. We will use focused ion beam and laser ablation to make samples for micromechanical tests, including micropillar compression and microbeam bending. To assess composition and tissue age, quantitative backscattered microscopy, neutral red staining and vibrational optical microscopy (Raman and FTIR) will be performed. We will also investigate chemical modifications i.e. phosphorylation and glycation in vitro on bone samples as well as isolated noncollagneous proteins (major component of CLs) as a model system. We will use multivariate linear regression models to uncover relationships between mechanics, composition, modification and medical history of donors. The properties of cement lines are heavily understudied, yet they are an important locus for fracture resistance in cortical bone. We offer an innovative approach to fill this gap that and to further our understanding of bone fracture mechanics. It will inspire new computer models and may also impact future fracture prediction of bone. Results will also be applicable for biomaterials research and bioinspired design.

• DFG Programme: Research Grants
• International Connection: Austria, Denmark, USA
• Partner Organisation: Fonds zur Förderung der wissenschaftlichen Forschung (FWF)
• Cooperation Partners: Privatdozent Dr. Markus Hartmann; Professor Dr. Daniel Kiener; Dr. Eleftherios Paschalis; Professor Dr. Esben Skipper Sorensen; Professor Dr. Philipp J. Thurner; Professor Dr. Deepak Vashishth