Measurement of Changes in Mechanical and Viscoelastic Properties of Cancer-induced Rat Tibia by using Nanoindentation

The aim of this research is to evaluate the changes in mechanical and viscoelastic properties of cancer induced rat tibias and to establish a correlation between viscosity and elastic modulus. Nanoindentation was conducted up to a magnitude of force equivalent to 500 nm with a load rate of 20 nm/s. After a 30-seconds peak hold time, the indenter was unloaded. A total of 30 indentations were made, each at least 30 pm away from an adjacent indentation surrounding canaliculae in the bone structure. Creep displacement-time curve was fitted using the following equation: h(2)(t)=(pi/2)P(0)cot alpha[(1-exp(-tE/eta))/E]. Viscosity was computed based on the curve fitting of creep displacement by non-linear regression. Cancer-induced tibias showed significantly lower indentation viscosity and modulus than sham-operated ones (p<0.05). Positive linear relationships were found between indentation modulus and viscosity for both cancer-induced and sham-operated tibias. However, there is no significant difference in the correlation between cancer-induced and sham-operated rat tibias (p>0.05).