Kyriacos Zygourakis

Research Interests:

Cellular and Tissue Engineering

Chemical Reaction Engineering

Education:

Ph.D. University of Minnesota (1981)

Dipl. Chem. Eng., National Technical University, Athens, Greece (1975)

My research interests span several important areas of bioengineering and reaction engineering. Applied mathematics, computer simulations, video microscopy, and digital image processing are integral parts of my research methodology.

Dynamic Behavior of Cell Populations Growing Under Mass Transport Limitations: Tissue growth in biomimetic scaffolds is strongly influenced by the dynamics and the heterogeneity of cell populations. A significant source of heterogeneity is the depletion of nutrients and growth factors due to transport limitations. Cells slow down, stop dividing or even die when the concentrations of key nutrients and growth factors drop below certain levels in the scaffold interior. As a result, tissue engineers have not yet been able to grow in vitro tissue samples thicker than a few millimeters for metabolically active cells.

In order to better understand these processes, my group is developing a multi-scale, hybrid framework that integrates biology with mathematical, computational, and experimental tools to study heterogeneous cell populations growing in three-dimensional scaffolds. We use a discrete, stochastic model to describe the population dynamics of migrating, interacting and proliferating cells. The diffusion and consumption of nutrients and growth factors are modeled by partial differential equations that are subject to boundary conditions appropriate for the bioreactors used in each case. These PDEs are solved numerically and the computed concentration profiles are fed to receptor-mediated binding/trafficking models or simplified kinetic expressions (i.e. Monod kinetics) to modulate cell proliferation rates and migration speeds. To meet the significant computational requirements of this model, parallel implementations of the hybrid algorithms have been developed for Linux clusters.

Finally, video microscopy and digital image analysis are used to experimentally observe the dynamic behavior of cell populations and find how cell migration and proliferation are influenced by the concentrations of nutrients and growth factors in the culture media, as well as by cell-substrate interactions.

Gas-solid and Liquid-Solid Reactions: Our research in this area focuses on the dynamic behavior of gas-solid or liquid-solid reacting systems with temporally evolving structures. Theoretical and experimental studies are carried out to determine which structural and process parameters control (a) the reactivity of porous carbonaceous materials and (b) the release rates of bioactive agents from multicomponent bioerodible systems. State-of-the-art video microscopy and digital image processing facilities support the experimental studies on coal pyrolysis and combustion. Our primary objective here is the analysis of transient phenomena such as coal particle swelling, macropore formation and heterogeneous or homogeneous ignitions. This information is crucial for the development of theoretical models that can be used for the optimal design of coal utilization processes.

Design of Catalytic Reactors for Air Pollution Control: We are working to develop integrated computer simulation and visualization tools for the optimal design of emission control reactors that incorporate some the most advanced adsorption and catalytic reaction technologies. Computer simulation is essential for the application of these technologies because of the complex interactions of transport, adsorption, heterogeneous reaction and catalyst deactivation phenomena occurring in emission control reactors. Optimization tools are also incorporated in our codes to allow for easy determination of optimal values of process parameters. These simulators will move computer-aided design into the hands of reactor engineers, so that they can meet the air pollution control challenges in small and medium-size operations.

Selected Publications

1. B. B. Youssef G. Cheng, K. Zygourakis and P. Markenscoff, “Parallel Implementation of a Cellular Automaton Modeling the Growth of Three-Dimensional Tissues,” J. High Perf. Comp. Applications, in press.
2. G. Cheng, B. B. Youssef P. Markenscoff and K. Zygourakis, “Cell Population Dynamics Modulate the Rates of Tissue Growth Processes,” Biophysical J., 90, 713-724 (2006).
3. G. Cheng and K. Zygourakis, “Cell Migration,” Tissue Engineering and Artificial Organs, J. D. Bronzino, Ed., Taylor and Francis, CRC Press (2006).
4. H. Shin, K. Zygourakis, M. C. Farach-Carson, M. J. Yaszemski, A. G. Mikos, “Modulation of differentiation and mineralization of marrow stromal cells cultured on biomimetic hydrogels modified with Arg-Gly-Asp containing peptides,” J. Biomed. Mater. Res. Part A, 69A, 535-543 (2004)
5. S. Perkins, II and K. Zygourakis, “Detection and Characterization of Coal and Char Particle Ignitions,” Ind. Eng. Chem. Res. 43, 3085-3091 (2004).
6. H. Shin, K. Zygourakis, M. C. Farach-Carson, M. J. Yaszemski and A. G. Mikos, "Attachment, proliferation, and migration of marrow stromal osteoblasts cultured on biomimetic hydrogels modified with an osteopontin-derived peptide," Biomaterials, 25, 895–906 (2004).
7. E. Behravesh, K. Zygourakis, and A.G. Mikos, “Adhesion and Migration of Marrow-Derived Osteoblasts on in Situ Crosslinkable Poly(propylene fumarate co-ethylene glycol) Based Hydrogels with a Covalently Linked RGDS Peptide for Bone Tissue Engineering,” J Biomed Mater Res., 65A, 261–271 (2003).
8. Y. Cai and K. Zygourakis, “A Multi-Scale Transient Model for Combustion of Highly Porous Chars,” Ind. Eng. Chem. Research, 42, 2746-2755 (2003).
9. E. Behravesh, S. Jo, K. Zygourakis and A. G. Mikos, "Synthesis of In Situ Crosslinkable Macroporous Biodegradable Poly(Propylene Fumarate-b-Ethylene Glycol) Hydrogels,” Biomacromolecules, 3, 374-381 (2002).
10. S. Kouvroukoglou, K. C. Dee, R. Bizios, L.V. McIntire and K. Zygourakis, "Endothelial Cell Migration on Surfaces Modified with Covalently-Bound Adhesive Peptides," Biomaterials, 21, 1725-1733 (2000).
11. A.J. Bergman and K. Zygourakis, "Migration of lymphocytes on fibronectin-coated surfaces: temporal evolution of migratory parameters," Biomaterials, 20, 2235-2244 (1999).

CHEMICAL & BIOMOLECULAR ENGINEERING DEPT. MS-362
Rice University PO Box 1892 Houston, Texas 77251-1892	E-mail: chbe@rice.edu	Phone: (713) 348-4902 FAX:(713) 348-5478