Browsing by Author "Anand, A."

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    Detection of Calcium-induced morphological changes on RBCs by digital holographic microscopy and blinking optical tweezers
    (IEEE, 2016) Rad, V. F.; Tavakkoli, R.; Moradi, Ali-Reza; Anand, A.; Javidi, B.
    Ca+2 level in the circulating red blood cells (RBCs) takes part not only in controlling biophysical properties, but also affects the membrane composition, and its morphological and rheological properties. Excessive accumulation of Ca2+ within the cells is associated with a number of important pathological diseases. In this paper, by the use of digital holographic microscopy (DHM), we quantitatively analyzed the volumetric behavior of RBC membrane under influence of excess Calcium ions. DHM in a transmission mode is an effective tool for quantitative visualization of phase objects. By deriving the associated phase changes 3D information on the morphology variation of the cells at arbitrary time scales is obtained. Individual cells are immobilized by the use of optical tweezers and are monitored live with DHM system, while the concentration of Ca2+ ions in the buffer is changed simultaneously. We utilized blinking optical tweezers, by inserting an optical chopper to modulate intensity of the trapping laser beam. Blinking optical tweezers, while keeping the cell trapped during the experiments, ensures of minimizing the photo-damage of trapping laser beam on the cell. Our experimental results are in agreement with previous biological studies and predictions, and experimental observations of living RBCs under Ca2+ influence.
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    Microsphere-Assisted Super-Resolved Mirau Digital Holographic Microscopy for Cell Identification
    (OSA - The Optical Society, 2017) Aakhte, M.; Abbasian, V.; Akhlaghi, E. A.; Moradi, A. R.; Anand, A.; Javidi, B.
    In this paper, we use a glass microsphere incorporated into a digital holographic microscope to increase the effective resolution of the system, aiming at precise cell identification. A Mirau interferometric objective is employed in the experiments, which can be used for a common-path digital holographic microscopy (DHMicroscopy) arrangement. High-magnification Mirau objectives are expensive and suffer from low working distances, yet the commonly used low-magnification Mirau objectives do not have high lateral resolutions. We show that by placing a glass microsphere within the working distance of a low-magnification Mirau objective, its effective numerical aperture can be increased, leading to super-resolved three-dimensional images. The improvement in the lateral resolution depends on the size and vertical position of microsphere, and by varying these parameters, the lateral resolution and magnification may be adjusted. We used the information from the super-resolution DHMicroscopy to identify thalassemia minor red blood cells (tRBCs). Identification is done by comparing the volumetric measurements with those of healthy RBCs. Our results show that microsphere-assisted super-resolved Mirau DHMicroscopy, being common path and off-axis in nature, has the potential to serve as a benchtop device for cell identification and biomedical measurements.