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Thesis
Peer Reviewed

Developing a Multimodal System to Study Cellular Injuries, with the Focus on Traumatic Brain Injury

Pouladian, Pegah
Advisor(s): Preece, Daryl

UC Irvine Electronic Theses and Dissertations (2023)

Traumatic Brain Injury (TBI) is a significant public health concern. The Centers for DiseaseControl and Prevention reported a notable increase in TBI-related incidents from 2006 to 2014. TBI occurs when an external force disrupts the normal function of the brain, leading to a range of outcomes, from mild to severe, with consequences ranging from full neurological recovery to mortality. Despite advances, TBI remains a leading cause of physical impairment and death, particularly among young people. This work focuses on developing a multimodal microscopy system that includes a custom- made, cost-effective Quantitative Phase Microscope (QPM) that is a pivotal tool in label-free imaging of transparent specimens, especially in cell biology. This microscopy system supports fluorescence imaging, enhancing flexibility for studying cellular structures and dynamics. The microscopy system is a promising tool for simulating traumatic brain injury in vitro, as it is integrated with a Laser-Induced Shockwave (LIS) system. The LIS system generates con- trolled shockwaves for brief shear stress applications to replicate conditions similar to those experienced in TBI. Optical Trapping (OT), using continuous laser light manipulation, is also combined with the LIS system, creating a versatile platform to investigate the interplay between shockwaves and optical trapping effects on biological specimens, particularly for xi single-cell manipulation. This integrated approach significantly improves the understand- ing of dynamic cellular responses, morphological changes, and intracellular dynamics under controlled conditions. A section of the thesis is dedicated to quantitative phase image processing, providing method- ologies to convert raw camera images into precise heightmaps, and addressing challenges in cell segmentation and feature extraction. The chapter aims to equip researchers with scien- tifically accurate tools for analyzing cellular structures. In the final chapter, we investigate the response of astrocyte cells to laser-induced shock- waves, focusing on morphological characteristics such as surface area, volume, and circular- ity. We chose astrocytes as the focal point of this investigation because astrocytes undergo a defense mechanism called astrogliosis when triggered. The experimental setup involves control and shockwave-exposed groups in a custom-made heating chamber with tightly con- trolled environmental conditions. Statistical analysis reveals significant differences in cellular parameters, providing insights into the impact of shockwaves on astrocyte cell morphology. This chapter contributes to understanding cellular responses to mechanical stimuli and opens avenues for further investigations into underlying mechanisms. Overall, the thesis offers a scientific exploration of advanced microscopy techniques and their applications in studying cellular dynamics and responses.

Cover page: Developing a Multimodal System to Study Cellular Injuries, with the Focus on Traumatic Brain Injury

Article
Peer Reviewed

Applications of Optically Controlled Gold Nanostructures in Biomedical Engineering

UC Irvine Previously Published Works (2020)

Since their inception, optical tweezers have proven to be a useful tool for improving human understanding of the microscopic world with wide-ranging applications across science. In recent years, they have found many particularly appealing applications in the field of biomedical engineering which harnesses the knowledge and skills in engineering to tackle problems in biology and medicine. Notably, metallic nanostructures like gold nanoparticles have proven to be an excellent tool for OT-based micromanipulation due to their large polarizability and relatively low cytotoxicity. In this article, we review the progress made in the application of optically trapped gold nanomaterials to problems in bioengineering. After an introduction to the basic methods of optical trapping, we give an overview of potential applications to bioengineering specifically: nano/biomaterials, microfluidics, drug delivery, biosensing, biophotonics and imaging, and mechanobiology/single-molecule biophysics. We highlight the recent research progress, discuss challenges, and provide possible future directions in this field.

Cover page: Applications of Optically Controlled Gold Nanostructures in Biomedical Engineering

Creative Commons 'BY' version 4.0 license

Article
Peer Reviewed

Conservation of orbital angular momentum and polarization through biological waveguides

UC Irvine Previously Published Works (2022)

A major roadblock to the development of photonic sensors is the scattering associated with many biological systems. We show the conservation of photonic states through optically self-arranged biological waveguides, for the first time, which can be implemented to transmit light through scattering media. The conservation of optical properties of light through biological waveguides allows for the transmission of high bandwidth information with low loss through scattering media. Here, we experimentally demonstrate the conservation of polarization state and orbital angular momentum of light through a self-arranged biological waveguide, several centimeters long, in a sheep red blood cell suspension. We utilize nonlinear optical effects to self-trap cells, which form waveguides at 532 nm and 780 nm wavelengths. Moreover, we use the formed waveguide channels to couple and guide probe beams without altering the information. The formed biological waveguides are in a sub-diffusive scattering regime, so the photons' information degrades insignificantly over several centimeters of propagation through the scattering media. Our results show the potential of biological waveguides as a methodology for the development of novel photonic biosensors, biomedical devices that require optical wireless communication, and the development of new approaches to noninvasive biomedical imaging.

Cover page: Conservation of orbital angular momentum and polarization through biological waveguides

Article
Peer Reviewed

Effect of red light on optically trapped spermatozoa

UC Irvine Previously Published Works (2017)

Successful artificial insemination relies on the use of high quality spermatozoa. One measure of sperm quality is swimming force. Increased swimming force has been correlated with higher sperm swimming speeds and improved reproductive success. It is hypothesized that by increasing sperm swimming speed, one can increase swimming force. Previous studies have shown that red light irradiation causes an increase in sperm swimming speed. In the current study, 633nm red light irradiation is shown to increase mean squared displacement in trapped sperm. The methodology allows for comparison of relative swimming forces between irradiated and non-irradiated samples.

Cover page: Effect of red light on optically trapped spermatozoa

Article
Peer Reviewed

Mitotic tethers connect sister chromosomes and transmit "cross-polar" force during anaphase A of mitosis in PtK2 cells.

UC Irvine Previously Published Works (2017)

Originally described in crane-fly spermatocytes, tethers physically link and transmit force between the ends of separating chromosomes. Optical tweezers and laser scissors were used to sever the tether between chromosomes, create chromosome fragments attached to the tether which move toward the opposite pole, and to trap the tethered fragments. Laser microsurgery in the intracellular space between separating telomeres reduced chromosome strain in half of tested chromosome pairs. When the telomere-containing region was severed from the rest of the chromosome body, the resultant fragment either traveled towards the proper pole (poleward), towards the sister pole (cross-polar), or movement ceased. Fragment travel towards the sister pole varied in distance and always ceased following a cut between telomeres, indicating the tether is responsible for transferring a cross-polar force to the fragment. Optical trapping of cross-polar traveling fragments places an upper boundary on the tethering force of ~1.5 pN.

Cover page: Mitotic tethers connect sister chromosomes and transmit "cross-polar" force during anaphase A of mitosis in PtK2 cells.

Article
Peer Reviewed

Independent polarisation control of multiple optical traps

UC Irvine Previously Published Works (2008)

We present a system which uses a single spatial light modulator to control the spin angular momentum of multiple optical traps. These traps may be independently controlled both in terms of spatial location and in terms of their spin angular momentum content. The system relies on a spatial light modulator used in a "split-screen" configuration to generate beams of orthogonal polarisation states which are subsequently combined at a polarising beam splitter. Defining the phase difference between the beams with the spatial light modulator enables control of the polarisation state of the light. We demonstrate the functionality of the system by controlling the rotation and orientation of birefringent vaterite crystals within holographic optical tweezers.

Cover page: Independent polarisation control of multiple optical traps

Article
Peer Reviewed

Red Light Irradiation of Human Spermatozoa Increases Motility without Significant DNA Damage

UC Irvine Previously Published Works (2017)

Red light has been shown to increase sperm swimming speeds, but there is little characterization of its effect on DNA or swimming force. In this study 633nm laser light irradiation did not induce significant levels of oxidative DNA damage.

Cover page: Red Light Irradiation of Human Spermatozoa Increases Motility without Significant DNA Damage

Article

Investigation of astrocytes’ morphological changes in response to laser-induced shockwave

UC Irvine Previously Published Works (2023)

Abstract: Traumatic Brain Injury (TBI) arises from an external force affecting the brain, leading to a range of outcomes from mild to severe. Despite continuous scientific advancements, it continues to pose a persistent threat and remains a significant cause of physical impairment and mortality. Various models, including blast-induced TBI (bTBI), have been proposed to simulate TBI. Laser-induced shockwaves (LIS) us emerging as an effective method. LIS generates shockwaves via pulsed laser-induced plasma formation, offering a controlled means to study TBI at the cellular level. Astrocytes, pivotal in maintaining brain function post-injury, undergo dynamic morphological changes, contributing to the understanding of injury responses and neurodegenerative diseases. This study introduces a system combining Laser-Induced Shockwaves (LIS) and Quantitative Phase Microscopy (QPM) to quantify morphological changes in astrocytes during and after LIS exposure. QPM, a label-free method, facilitates 3D imaging and captures real-time cellular dynamics. The integration of LIS and QPM enables the assessment of astrocyte responses to shear stress caused by LIS, revealing immediate and sustained morphological transformations. Analysis post-LIS exposure indicates significant alterations in circularity, volume, surface area, and other features. Statistical tests affirm of observed trends, providing insights into astrocyte responses to mechanical forces. The findings contribute to understanding how mechanical stimuli impact astrocyte morphology, holding promise for targeted therapeutic strategies in traumatic brain injuries and related neurological disorders. The integrated LIS and QPM approach serves as a powerful tool for 3D imaging and quantitative measurement of astrocyte morphological changes, offering deeper insights into cellular dynamics and potential therapeutic interventions.

Cover page: Investigation of astrocytes’ morphological changes in response to laser-induced shockwave

Article
Peer Reviewed

Scattering of Sculpted Light in Intact Brain Tissue, with implications for Optogenetics

UC Irvine Previously Published Works (2015)

Optogenetics uses light to control and observe the activity of neurons, often using a focused laser beam. As brain tissue is a scattering medium, beams are distorted and spread with propagation through neural tissue, and the beam's degradation has important implications in optogenetic experiments. To address this, we present an analysis of scattering and loss of intensity of focused laser beams at different depths within the brains of zebrafish larvae. Our experimental set-up uses a 488 nm laser and a spatial light modulator to focus a diffraction-limited spot of light within the brain. We use a combination of experimental measurements of back-scattered light in live larvae and computational modelling of the scattering to determine the spatial distribution of light. Modelling is performed using the Monte Carlo method, supported by generalised Lorenz-Mie theory in the single-scattering approximation. Scattering in areas rich in cell bodies is compared to that of regions of neuropil to identify the distinct and dramatic contributions that cell nuclei make to scattering. We demonstrate the feasibility of illuminating individual neurons, even in nucleus-rich areas, at depths beyond 100 μm using a spatial light modulator in combination with a standard laser and microscope optics.

Cover page: Scattering of Sculpted Light in Intact Brain Tissue, with implications for Optogenetics

Article
Peer Reviewed

Fluid Shear Stress Enhances the Phagocytic Response of Astrocytes

UC Irvine Previously Published Works (2020)

Astrocytes respond to brain injury at a cellular level by the process of reactive astrogliosis, and are able to adjust their response according to the severity of the insult. Included in the reactive response is the process of phagocytosis, where astrocytes clean up surrounding cellular debris from damaged cells. In this study, we observe the process of phagocytosis by primary cortical astrocytes in the presence of media flow across the apical surface of the cells. Both static and cells under flow conditions respond consistently via phagocytosis of laser-induced cellular debris. We found that astrocytes exposed to shear flow initiate phagocytosis at a consistently faster rate than cells observed under static conditions. Shear forces created by laminar flow were analyzed as well as the flow fields created around astrocyte cells. Results suggest astrocyte phagocytosis is a mechanosensitive response, thus revealing the potential to enhance astrocyte phagocytic cleanup of damaged nervous tissue.

Cover page: Fluid Shear Stress Enhances the Phagocytic Response of Astrocytes