Combining quantitative phase microscopy and laser-induced shockwave for the study of cell injury

Abstract

In this paper, we propose a new system for studying cellular injury. The system is a biophotonic work station that can generate Laser-Induced Shockwave (LIS) in the cell culture medium combined with a Quantitative Phase Microscope (QPM), enabling the real-time measurement of intracellular dynamics and quantitative changes in cellular thickness during the damage and recovery processes. In addition, the system is capable of Phase Contrast (PhC) and Differential Interference Contrast (DIC) microscopy. Our studies showed that QPM allows us to discern changes that otherwise would be unnoticeable or difficult to detect using phase or DIC imaging. As one application, this system enables the study of traumatic brain injury in vitro. Astrocytes are the most numerous cells in the central nervous system (CNS) and have been shown to play a role in the repair of damaged neuronal tissue. In this study, we use LIS to create a precise mechanical force in the culture medium at a controlled distance from astrocytes and measure the quantitative changes, in order of nanometers, in cell thickness. Experiments were performed in different cell culture media in order to evaluate the reproducibility of the experimental method.

Shining Light in Mechanobiology: Optical Tweezers, Scissors, and Beyond

“…By imaging phase changes or polarization changes in light passing through a cell rather than intensity changes, image enhancement can often be achieved. Quantitative phase microscopy utilizes interference to make measurements of phase changes in the light transmitted through microscopic objects such as cells. , Digital holographic microscopy uses a similar approach, interfering a coherent reference beam with the laser light transmitted through the sample. Spatial light modulators can be employed in this context to produce known phase shifts between the beams, enabling phase recovery from a series of 3 or more interference images.…”

“…In microscopic systems, these techniques can still be employed at scales close to the diffraction limit . However, when objects are transparent to light, other methodologies must be employed . The diffraction limit of the optical system limits the resolution of the images produced by these techniques.…”

“…146 However, when objects are transparent to light, other methodologies must be employed. 147 The diffraction limit of the optical system limits the resolution of the images produced by these techniques. One answer to this is structured illumination microscopy (SIM), 148−150 which applies periodic illumination patterns to a sample to utilize an increased frequency space and thereby improve image resolution.…”

Roadmap for optical tweezers

“…Typically, these techniques utilize interferometry-based imaging technology that retrieves information about an object under study by interrogating the phase structure of the transmitted or reflected light to gain multidimensional information about a sample, such as the 3D morphology of an object, its refractive index, and its associated dynamics. This results in a versatile label-free imaging modality that has attracted considerable research interest in quantitative biological cell imaging [365][366][367][368]. This method may be used to detect subcellular structures as well as the morphology of entire tissue slices, and because no external labelling is required, it can be used to assess dynamical processes from milliseconds to days [369].…”

Multimodal system for studying astrocyte cells, under quantitative phase microscope

“…Quantitative phase microscopy (QPM) is one of the leading methods for studying cellular morphology. This modality enables the imaging and quantification of transparent characteristics in cells, as well as the measurement of organelle movements and cellular dynamics, such as membrane motility [3,4]. The ability to manipulate a single cell without affecting other cells, or affecting a group of nearby cells with various degrees of force, in a cultured environment can be an effective way to study and simulate diseases that deal with cellular injuries, such as TBI.…”