Pathophysiology of human red blood cell probed by quantitative phase microscopy by YongKeun Park.

Thesis (Ph. D.)--Harvard-MIT Division of Health Sciences and Technology, 2010.Cataloged from PDF version of thesis.Includes bibliographical references (p. 53-58).There is a strong correlation between the membrane fluctuations and the material properties of living cells. The former, consisting of submicron displacements, can be altered by changing the cells' pathophysiological conditions. It is our hypothesis that the material properties of cells can be retrieved when we quantify cell membrane fluctuation and combine that result with an appropriate physical model. We have developed: (1) an optical imaging technique to noninvasively quantify membrane fluctuations in red blood cells at the nanometer and millisecond scales; and (2) a model to retrieve the material properties of red blood cell membrane. The technique employs laser interferometry and provides full-field quantitative topographical information of living cells with unprecedented stability. Integration with the mathematical model provides the specific material properties from individual cell membrane fluctuations: shear modulus of the membrane; bending modulus; and viscosity of the cytoplasm. Employing these methods, we have systemically studied the material properties of human red blood cells altered by various pathophysiological conditions: morphological transition of red blood cell; parasitization by the P. falciparum parasites; and metabolic remodeling of the membrane driven by Adenosine-5'- triphosphate (ATP). We envision that this investigation could offer a means to link cell membrane fluctuations with the pathological conditions that lead to human disease states by quantitatively providing the alternation in material properties. A clear understanding of the mechanical alteration of red blood cells is important to studying the human diseases which cause their infection.Ph.D

Cellular normoxic biophysical markers of hydroxyurea treatment in sickle cell disease

Hydroxyurea (HU) has been used clinically to reduce the frequency of painful crisis and the need for blood transfusion in sickle cell disease (SCD) patients. However, the mechanisms underlying such beneficial effects of HU treatment are still not fully understood. Studies have indicated a weak correlation between clinical outcome and molecular markers, and the scientific quest to develop companion biophysical markers have mostly targeted studies of blood properties under hypoxia. Using a common-path interferometric technique, we measure biomechanical and morphological properties of individual red blood cells in SCD patients as a function of cell density, and investigate the correlation of these biophysical properties with drug intake as well as other clinically measured parameters. Our results show that patient-specific HU effects on the cellular biophysical properties are detectable at normoxia, and that these properties are strongly correlated with the clinically measured mean cellular volume rather than fetal hemoglobin level.National Institutes of Health (U.S.) (Grant 1R01HL121386-01A1)National Institutes of Health (U.S.) (Grant 9P41EB015871-26A1)National Institutes of Health (U.S.) (Grant 5R01NS051320)National Institutes of Health (U.S.) (Grant 5U01HL114476)National Institutes of Health (U.S.) (Grant 4R44EB012415)National Science Foundation (U.S.) (Grant CBET-0939511

Cellular biophysical markers of hydroxyurea treatment in sickle cell disease

Using a common-path interferometric technique, we measure biomechanical and morphological properties of individual red blood cells in SCD patients as a function of cell density, and investigate the correlation of these biophysical properties with drug intake as well as other clinically measured parameters