Faculty Directory

Biomedical Research Society (BMES) Poster Award, Oct. 2006
Materials Research Society (MRS) Graduate Student Gold Award Winner, Dec. 2004
Whitaker Foundation Graduate Fellowship, 2002-2004
MIT Bioengineering Undergraduate Research Award, May 1999

We are investigating the mechanical properties of cardiac cells and differentiating stem cells separately and in co-culture and on different matrices using a combination of atomic force microscopy (AFM) and modeling techniques. The goal of this research is to determine when differentiating stem cells match the mechanical properties of the native cardiac cells, what factors are most important for the changes in mechanical properties and what signals affect the time course of differentiations.

The Hertz model, commonly used in literature to describe cell indentation data, is a simple analytical elastic isotropic theoretical model that can be used to extract quantitative measures of cell stiffness from AFM nanoindentation. However, this model does not capture the complex and dynamic mechanical behavior of most cells that are important for cell function. By correlating the levels of the cytoskeletal proteins to the measured mechanical response of different cell types, we can determine which proteins are most important in cell stiffness. Therefore, concurrent with the cell indentation experiments described above, we are developing theoretical models of cardiac and stem cell mechanics. These models will allow us to build a micro- to macro-scale model of cardiac tissue with varying amounts of each cell type.

Cell-cell interactions that form between cardiac cells over time are being directly characterized. The goal of this project is to understand how cellular adherence junctions form and how they change between the different cell types important for cardiac function and repair. Using AFM techniques, we can observe the formation of intercellular adherence junctions in real time.

J. D. Hemmer, J. Nagatomi, S. T. Wood, A. A. Vertegel, D. Dean, M. LaBerge, “Role of Cytoskeletal Components in Stress Relaxation Behavior of Adherent Vascular Smooth Muscle Cells”, ASME Journal of Biomechanical Engineering 131(4):041001 (2009).

L. Han, D. Dean, L. A. Daher, A. J. Grodzinsky, C. Ortiz, “Cartilage Aggrecan Can Undergo Self-Adhesion” Biophysical Journal 95(10):4862-4870, (2008)

J. D. Hemmer, D. Dean, A. Vertegel, E. Langan, M. LaBerge, “Effects of serum deprivation on the mechanical properties of adherent vascular smooth muscle cells.” Proceedings of the IMechE Part H: Journal of Engineering in Medicine 222(H5): 761-772, (2008)

S. Deitch, C. Kunkle, X. Cui, T. Boland, D. Dean, “Collagen Matrix Alignment Using Inkjet Printer Technology.” Mater. Res. Soc. Symp. Proc. 1094: DD07-16, (2008)

Han, L., Dean, D., Mao, P., Ortiz, C., Grodzinsky, A. J., “Nanoscale Shear Deformation Mechanisms of Opposing Cartilage Aggrecan Macromolecules” Biophysical Journal, 2007 93(5):L23-25, (2007)

Han, L., Dean, D., Ortiz, C., Grodzinsky, A. J., “Lateral Nanomechanics of Cartilage Aggrecan Macromolecules”, Biophysical Journal 92:1384-1398, (2007)

Pirlo, R. K., Dean, D., Knapp, D. R., Gao, B. Z., “Cell Deposition System Based on Laser Guidance”, Biotechnology Journal 1(9):1007-13 (2006)

Dean, D., Han, L., Grodzinsky, A. J., and Ortiz, C., “Compressive Nanomechanics of Opposing Aggrecan Macromolecules,” Journal of Biomechanics 39(14): 2555-2565 (2006)

Vandiver, J., Dean, D., Patel, N., Botelho, C., Best, S., Santos, J., Lopes, M., Bonfield, W., and Ortiz, C., “Silicon addition to hydroxyapatite increases nanoscale electrostatic, van der Waals, and adhesive interactions," Journal of Biomedical Materials Research A 78A(2):352-363 (2006).

Dean, D., Han, L., Ortiz, C., and Grodzinsky, A. J., “Nanoscale Conformation and Compressibility of Cartilage Aggrecan using Microcontact Printing and Atomic Force Microscopy,” Macromolecules 38(10); 4047-4049 (2005)

Seog, J., Dean, D., Rolauffs, B., Wu, T., Genzer, J., Plaas, A.H.K., Grodzinsky, A. J., and Ortiz, C. “Nanomechanics of Opposing Glycosaminoglycan Macromolecules,” Journal of Biomechanics.38(9); 1789-1797 (2005)

Vandiver, J., Dean, D., Patel, N., Bonfield, W., and Ortiz, C., “Nanoscale Variation in Surface Charge of Synthetic Hydroxyapatite Detected by Chemically and Spatially Specific High Resolution Force Spectroscopy,” Biomaterials, 26(3): 271-283 (2005)

Fitzgerald, J., Jin, M., Dean, D., Wood, D., Zheng, M., Grodzinsky, A. “Mechanical Compression of Cartilage Explants Induces Multiple Time-Dependent Gene Expression Patterns and Involves Intracellular Calcium and Cyclic AMP,” Journal of Biological Chemistry, 279(19): 19502 (2004).

Seog, J., Dean, D., Frank, E., Ortiz, C., Grodzinsky, A. “Preparation of End-Grafted Polyelectrolytes On Nanoscale Probe Tips Using An Electric Field,” Macromolecules 37(3) 1156-1158 (2004)

Rixman, M. A., Dean, D., and Ortiz, C. “Nanoscale Intermolecular Interactions between Human Serum Albumin and Low Grafting Density Surfaces of Poly(ethylene oxide)” Langmuir 19 (22); 9357-9372 (2003)

Dean, D., Seog, J., Ortiz, C., and Grodzinsky, A.. “Molecular Level Theoretical Model for Electrostatic Interactions Within Polyelectrolyte Brushes Using Glycosaminoglycans as a Model System” Langmuir, 19(13): 5526-5539 (2003)

Rixman, M. A., Dean, D., Mathias, C. E., Ortiz, C. “Nanoscale Intermolecular Interactions between Human Serum Albumin and Alkanethiol Self-Assembled Monolayers,” Langmuir, 19(15) 6202-6218 (2003)

Seog, J., Dean, D., Plaas, A, Wong-Palms, S., Grodzinsky, A., and Ortiz, C.. “Direct Measurement of Glycosaminoglycan Intermolecular Interactions via High-Resolution Force Spectroscopy,” Macromolecules, 35(14):5601-5615 (2002)