Characterizing forces imparted on cells using laser-induced shockwaves (Conference Presentation)

Traumatic Brain Injury (TBI) occurs when an external force injures the brain. While clinical outcomes of TBI can vary widely in severity, few mechanisms of neurodegeneration following TBI have been identified for treatment. Understanding mechanotransduction in cells is key to understanding cellular response to injury. This has been previously studied using a variety of optical techniques such as laser tweezers, laser ablation, and others. We propose a model utilizing photodisruption for studying the early pathogenesis of TBI in primary neuron cultures by generating laser-induced shockwaves (LISs). Photodisruption allows for the generation of spatiotemporally defined shear stress against cells. The shear stress exerted by the shockwave is between 0 - 50 kPa depending on the distance from the shockwave epicenter. Cells typically situated at a distance from the epicenter of 50 m undergo necrosis while viability is preserved for those located at a distance of 100 m. An optical system was developed that allows single cells to be selectively studied in response to LISs. Approximate timescales of each of the effects culminating in shockwave generation span several orders of magnitude from nanoseconds to milliseconds. Thus, our system utilizes Pockels cells — a high-speed, electro-optical shutter — to capture shockwave dynamics. The force measurement system is characterized by imaging stages over the period of cavitation then, violent expansion and collapse of microbubbles responsible for shockwave generation. Here, we visualize LISs and observe subsequent, morphological responses elicited by cells under a range of forces generated from optical breakdown.