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Hypotonic stimulation is known to cause morphological changes in cells and also leads to modulation of cellular physiology. In order to evaluate the dynamics of cellular response to hypotonic stimulation, we utilized digital holographic microscopy for quantitative phase microscopy, achieved by a common-path interferometry geometry based on extraction of reference beam by spatial-filtering. Results from live cell investigations demonstrate the capability of this method for dynamic quantitative phase imaging. Further, wavelet and multi-fractal detrended fluctuation analysis revealed that the dynamic phase changes, in response to hypotonic stimulation, are multifractal in nature. [ABSTRACT FROM AUTHOR]

Quantitative phase microscopy (QPM) allows dynamic mapping of optical path length of microscopic samples with high temporal and axial resolution. However, decoupling of the geometric thickness from the refractive index in phase measurements is challenging. Here, we report use of optical tweezers combined with QPM for decoupling geometric thickness from the refractive index. This is demonstrated by orienting the microscopic sample (red blood cell) by optical tweezers and imaging the phase at various orientations. Since optical tweezers can orient wide variety of micro and nanoscopic objects, this integrated method can be employed to accurately determine their physical properties. [ABSTRACT FROM AUTHOR]

We report a novel technique for label-free, rapid visualization of structure and dynamics of live cells with nanoscale sensitivity through traditionally opaque media. Specifically, by combining principles of near-infrared (NIR) spectroscopy and quantitative phase imaging, functional characterization of cellular structure and dynamics through silicon substrates is realized in our study. We demonstrate the efficacy of the new approach by full-field imaging of erythrocyte morphology in their native states with a nm path length sensitivity. Additionally, we observe dynamic variations of human embryonic kidney cells, through a silicon substrate, in response to hypotonic stimulation with ms temporal resolution that also provides unique insight into the underlying biophysical changes. The proposed technology is fundamentally suited for high-performance investigations of biological specimens and significantly expands the options for visualization in complex microfluidic devices fabricated on silicon [ABSTRACT FROM AUTHOR]