Biology subjects

Dougan, C.

Publications and source records attributed to Dougan, C..

2 recordsLinked to original sources

bioRxiv2022

Cavitation Induced Fracture of Intact Brain Tissue

Nonpenetrating traumatic brain injuries (TBI) are linked to cavitation. The structural organization of the brain makes it particularly susceptible to tears and fractures from these cavitation events, but limitations in existing characterization methods make it difficult to understand the relationship between fracture and cavitation in this tissue. More broadly, fracture energy is an important, yet often overlooked, mechanical property of all soft tissues. We combined needle-induced cavitation (NIC) with hydraulic fracture models to induce and quantify fracture in intact brains at precise locations. We report here the first measurements of the fracture energy of intact brain tissue that range from 1.5 to 8.9 J/m2, depending on the location in the brain and the model applied. We observed that fracture consistently occurs along interfaces between regions of brain tissue. These fractures along interfaces allow cavitation-related damage to propagate several millimeters away from the initial injury site. Quantifying the forces necessary to fracture brain and other soft tissues is critical for understanding how impact and blast waves damage tissue in vivo and has implications for the design of protective gear and tissue engineering. SignificanceMild injuries associated with concussion and blast waves cause tearing of brain tissue, which leads to traumatic brain injury (TBI). TBI is a leading cause of death and disability among children and young adults in the U.S., with 1.5 million Americans reporting a TBI each year. We introduce a novel approach to visualize these tears in intact brain tissue, and report the energies associated with brain fracture. Quantifying the fracture energy of brain, as we have done here, is critical to understand the forces from injury that lead to TBI.

bioengineering↗

bioRxiv2018

Cross-Platform Mechanical Characterization of Lung Tissue

Published data on the mechanical strength and elasticity of lung tissue is widely variable, primarily due to differences in how testing was conducted across individual studies. This makes it extremely difficult to find a benchmark modulus of lung tissue when designing synthetic extracellular matrices (ECMs). To address this issue, we tested tissues from various areas of the lung using multiple characterization techniques, including micro-indentation, small amplitude oscillatory shear (SAOS), uniaxial tension, and cavitation rheology. We report the sample preparation required and data obtainable across these unique but complimentary methods to quantify the modulus of lung tissue. We highlight cavitation rheology as a new method, which can measure the modulus of intact tissue with precise spatial control, and reports a modulus on the length scale of typical tissue heterogeneities. Shear rheology, uniaxial, and indentation testing require heavy sample manipulation and destruction; however, cavitation rheology can be performed in situ across nearly all areas of the lung with minimal preparation. The Youngs modulus of bulk lung tissue using microindentation (1.9{+/-}0.5 kPa), SAOS (3.2{+/-}0.6 kPa), uniaxial testing (3.4{+/-}0.4 kPa), and cavitation rheology (6.1{+/-}1.6 kPa) were within the same order of magnitude, with higher values consistently reported from cavitation, likely due to our ability to keep the tissue intact. Although cavitation rheology does not capture the non-linear strains revealed by uniaxial testing and SAOS, it provides an opportunity to measure mechanical characteristics of lung tissue on a microscale level on intact tissues. Overall, our study demonstrates that each technique has independent benefits, and each technique revealed unique mechanical features of lung tissue that can contribute to a deeper understanding of lung tissue mechanics.

bioengineering↗