PURPOSE: Effects of in vitro induced nonenzymatic glycation of bone collagen on stiffness and fracture of demineralized bone matrix in unconfined compression were investigated. MATERIAL AND METHODS: Regular specimens from mid-shaft of bovine femur were grouped in pairs. One sample (R) from each pair was incubated in ribose solution, control samples (C) were incubated in a buffer solution. Samples were then demineralized in formic acid. Demineralized samples were axially compressed to failure (0.033/s). Direction of compression was along the longitudinal axis of femur (L) or perpendicular (transverse) to that (T). Mechanical behavior of demineralized samples was characterized in terms of secant modulus, stress, and strain at fracture and work to failure. The development of damage was examined in terms of acoustic emission (AE) signal recorded during loading. RESULTS: In L direction, strain at fracture following glycation was lower than in the controls (p=0.038); secant modulus and ultimate stress were not significantly different in R and C. In the transverse direction, strain at fracture in R was higher than in C (p=0.053), as well as work to failure (p=0.020). Anisotropy of bone matrix, defined in terms of a ratio of the parameters in two perpendicular directions, decreased markedly in ribosylated samples. Both the number of AE events and cumulative AE energy during deformation were significantly higher in ribosylated samples than in the control for both directions of compression. CONCLUSION: The study demonstrated that nonenzymatic glycation plays a significant role in modifying organic matrix properties in cortical bone.
PURPOSE: Effects of in vitro induced nonenzymatic glycation of bone collagen on stiffness and fracture of demineralized bone matrix in unconfined compression were investigated. MATERIAL AND METHODS: Regular specimens from mid-shaft of bovine femur were grouped in pairs. One sample (R) from each pair was incubated in ribose solution, control samples (C) were incubated in a buffer solution. Samples were then demineralized in formic acid. Demineralized samples were axially compressed to failure (0.033/s). Direction of compression was along the longitudinal axis of femur (L) or perpendicular (transverse) to that (T). Mechanical behavior of demineralized samples was characterized in terms of secant modulus, stress, and strain at fracture and work to failure. The development of damage was examined in terms of acoustic emission (AE) signal recorded during loading. RESULTS: In L direction, strain at fracture following glycation was lower than in the controls (p=0.038); secant modulus and ultimate stress were not significantly different in R and C. In the transverse direction, strain at fracture in R was higher than in C (p=0.053), as well as work to failure (p=0.020). Anisotropy of bone matrix, defined in terms of a ratio of the parameters in two perpendicular directions, decreased markedly in ribosylated samples. Both the number of AE events and cumulative AE energy during deformation were significantly higher in ribosylated samples than in the control for both directions of compression. CONCLUSION: The study demonstrated that nonenzymatic glycation plays a significant role in modifying organic matrix properties in cortical bone.