Session: 06-01-02: Injury and Damage Biomechanics II - Organ and Tissue Injury Biomechanics 2

Paper Number: 150203

150203 - A Generalized Atomistic Continuum Framework and Molecular Dynamics Approach for the Failure Analysis of Neuronal Cytoskeleton Components 

 To investigate the cellular-level mechanical injury thresholds for the brain it is needed to understand injury mechanisms at the sub-cellular level. The overall evaluation of neuron cell damage requires an aggregated model considering all three major parts which are axon, dendrites and cell body/soma. Now a days most of the models for neuron cells have been developed only for axons. Despite axon being the primary focus but to determine the holistic injury threshold, modeling for dendrites and cell body is also vital. Dendrites are projections of neurons that resemble a tree-like structure. The cell body is the central region of the neuron from which dendrites and axon extended. This contains the nucleus, different organelles and act as the metabolic center. Both dendrites and cell body are crucial for maintaining the neuron’s structural integrity as they have various sub cellular components which are different than axon.  In other words, a neuron cell damage analysis should include constitutive and failure properties of subcellular cytoskeleton components such as microtubule, spectrin, neurofilaments, actin, and MAP2, their structural elements, and lipid membranes. These filaments are the key load-bearing components to maintain the shape and structural integrity of the neuronal cytoskeleton. Recently, we have developed a three-stage atomistic continuum modeling to predict the constitutive behavior and failure of the spectrin filament.  We showed that the total force required to reach the failure point depends on the unfolding, stretching and interfacial forces on spectrin. Simulations were conducted using LAMMPS, the widely accessible molecular dynamics solver. The interatomic potentials for the interacting atoms and molecules were modeled using OPLS force fields. Medium to high strain rate analysis has given a range of failure strains for spectrin repeats. A standard gradual simulation process of energy minimization, equilibration, and application of uniaxial tensile stretching has followed. Here, we have found the failure strain of spectrin belongs to the range of 8%~10% with the application of a velocity 1 Å/ps at a strain rate of  10¹¹ . This finding is highly analogous to the mentioned theoretical atomistic continuum model for predicting the failure of spectrin. The range of failure strain for actin is 10%~12% while the applied velocity is 5 Å/ps at a strain rate of 10¹¹. Utilizing structural similarity and deformation mechanisms, here, we have proposed an atomistic continuum approach to predict the failure of microtubule, actin and MAP2. The validation of the proposed theoretical model has been discussed through molecular dynamics simulation and available experimental data.  

Presenting Author: Md Nahian Bin Hossain The University of Texas at Arlington

Presenting Author Biography: Graduate Research Assistant at Multiscale Mechanics and Physics Lab at UTA.

Authors:

Md Nahian Bin Hossain The University of Texas at Arlington
Ashfaq Adnan The University of Texas at Arlington
Sheikh Fahad Ferdous Pennsylvania State University at Harrisburg