Viscoelastic Properties of Human Autopsy Brain Tissues as Biomarkers for Alzheimer's Diseases

Objective: The present study investigates viscoelastic properties of human autopsy brain tissue via nanoindentation to find feasible biomarkers for Alzheimer's disease (AD) in $ex$ $vivo$ condition and to understand the mechanics of the human brain better, especially on the difference before and after progression of AD. Methods: Viscoelastic properties of paraformaldehyde-fixed, paraffin-embedded thin (8 $mu text{m}$) sectioned normal and AD affected human autopsy brain tissue samples are investigated via nanoindentation with a combined loading profile of a linear preloading and a sinusoidal loading at various loading frequencies from 0.01 to 10 $text{Hz}$. In 1200 indentation tests for ten human autopsy brain tissue samples from ten different subjects (five AD cases and five normal controls), viscoelastic properties such as Young's modulus, storage modulus, loss modulus, and loss factor of both gray and white matter brain tissues samples from normal and AD affected tissues were measured experimentally. Results: We found that the normal brain tissues have higher Young's modulus values than the AD affected brain tissues by 23.5$%$ and 27.9$%$ on average for gray and white matter, respectively, with statistically significant differences ($p< 0.0001$) between the normal and AD affected brain tissues. Additionally, the AD affected brain tissues have much h- gher loss factor than the normal brain tissues on lower loading frequencies. Significance: AD is one...
Source: IEEE Transactions on Biomedical Engineering - Category: Biomedical Engineering Source Type: research