Traumatic Brain Injury (TBI) is the result of external forces impacting the brain. Despite scientific progress, TBI remains a significant cause of impairment and mortality. Recently, laser-induced shockwave (LIS) has emerged as an effective method for TBI simulation. LIS generates shockwaves through pulsed laser-induced plasma formation, allowing for the controlled study of TBI at the cellular level. This study introduces a novel approach to examine cellular morphological changes in response to shear stress, focusing on astrocyte cell type AST-1, by combining LIS with quantitative phase microscopy (QPM). QPM is a label-free technique that allows for real-time cellular dynamics observation through 3D imaging. Integrating LIS and QPM assesses astrocyte responses to shear stress caused by LIS, revealing both immediate and sustained morphological changes. Post-LIS exposure analysis shows significant alterations in astrocyte circularity, volume, surface area, and other features. Statistical tests confirm these observed trends, providing valuable insights into astrocyte responses to mechanical forces. These findings enhance our understanding of how mechanical stimuli affect astrocyte morphology, which may offer the potential for identifying and developing therapeutic strategies in TBI and related neurological disorders.
Biological studies are increasingly using optical forces to study cellular behavior and intracellular interactions. In this talk, we discuss the use of optically generated forces in biomedical treatment and diagnostics with specific reference to traumatic brain injury (TBI). Our biophotonic workstation includes optical tweezers, quantitative phase microscopy, fluorescence imaging, and laser-induced shockwaves to study cellular damage. We discuss our studies on astrocyte damage repair mechanisms as well as how the optical toolbox enables the study of intracellular signaling and cellular dynamics and anatomy.
There is a need for new methodologies to investigate cell apoptosis and recovery, cell adhesion, and cell-cell interactions in cellular biology and neurobiology. Such systems should be able to induce localized cell injuries and measure damage responses from single cells. In this regard, pulsed lasers can be used to produce Laser- Induced Shockwaves (LIS), which can cause cell detachments and induce cellular membrane injuries, by applying shear force in order of µN . Furthermore, since the resulting shear force can increase membrane permeability, chemicals and markers can then be transferred into cells non-invasively. Continuous-wave lasers can be used as Optical Tweezers (OT), to apply non-contact delicate forces, as low as 0.1f N , and deliver materials into cells, and also move the cells to different locations. In this paper, we introduce a combination of modalities to apply variable forces, from femto to micro newtons, to cells. Our system consists of a 1060nm continuous laser light source for OT and a 1030nm femtosecond pulsed laser for generating LIS. To have a direct measurement of changes in the cellular thickness and membrane dynamics, the cells are imaged under a Quantitative Phase Microscope (QPM). Our microscope is capable of Differential-Interference Microscopy (DIC) and Phase-Contrast microscopy (PhC) and fluorescent microscopy, making it a unique system for studying cell injuries.
Traumatic brain injury (TBI) occurs when an external shock causes injury to the brain. The mechanism of the disease is not completely understood yet. Studies have shown that astrocytes play various roles following brain injury. However, the exact functional role of them after TBI is still a matter of debate. Laser-induced shock waves (LIS) can create a precise controllable mechanical force that is capable of injuring or lysing cells to simulate the brain injury at the cellular level. Here, we propose a system that enables us to induce injuries in CNS cells with LIS and observe the whole process under a Quantitative phase microscope (QPM). Our system is also capable of adding another laser for optically trapping the cells to keep them at a certain distance from the center of the shockwave, as this distance is one of the important factors which determines the level of injury.
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