We are developing several methods to utilize quantitative phase imaging (QPI) for molecular, structural, and mechanical characterization of cells, including cancer cells and red blood cells (RBCs). To obtain molecular information in addition to the high-resolution cell structure provided by QPI, we combine QPI with a second imaging modality, Förster resonance energy transfer (FRET), which is sensitive to nanoscale, distance-dependent, dynamic measurements of subcellular structures. These two imaging methods are merged to allow simultaneous analysis of the molecular and biophysical properties of cancer cells. We recently used QPI to measure the biophysical response of normal RBCs under mechanical stress using microfluidic chips. In addition, QPI was combined with microfluidic devices to enable high throughput implementation, translating the technique to be more clinically relevant. We also used QPI to analyze the deformations of adherent cancer cells in response to shear flow and retrieve the cellular viscoelastic parameters from displacements in the cellular center of mass. This QPI assay was employed to track stiffness changes during progressive stages of carcinogenesis; where cell stiffness was decreased by treating the adherent cancer cells chemically, proving that treated cells have significantly lower shear stiffness than untreated cells. Furthermore, based on the assessment of cell’s refractive index inhomogeneity, we have developed a new method for calculating disorder strength from QPI images to evaluate disorder strength, a measure of refractive index variance, as an indicator of mechanical properties. Since the bibliography found on cell rheology usually characterizes cell mechanical properties based on different metrics that depend strongly on the technique employed to perform the analysis, we have developed a novel method for estimating shear moduli from QPI shear assay that allows to compare QPI-derived metrics to atomic force microscopy.
Current Personnel Working on Functional Phase Imaging:
Silvia Ceballos, Ph.D.