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). QPI was used to measure membrane fluctuations of normal red blood cells (RBCs) and sickle-celled RBCs. Recently, we have 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. To obtain molecular information in addition to the high-resolution cell structure, QPI was complimented with a second imaging modality which was sensitive to optical absorption. We explored the use of two modalities, which were acquired simultaneously with QPI. The first was photothermal microscopy, which was sensitive to the temperature-related change in the refractive index induced by optical absorption. A novel wide-field optical lock-in technique was used to enhance SNR. The second was photoacoustic microscopy, in which the local optical absorption generates thermo-elastic expansion, producing acoustic waves. Both techniques were demonstrated on cancer cells tagged with anti-Epidermal Growth Factor Receptor (EGFR) conjugated gold nanoparticles.
Current Personnel Working on Functional Phase Imaging: