Texas Tech University

Dr. Dimitri Pappas

Pappas

Title: Associate Professor

Education: Ph.D., University of Florida, 2002; Postdoctoral Study, University of Florida, 2002

Research Area: Analytical Chemistry

Office: Chemistry 300-B

Phone: 806-834-1103

Email: d.pappas@ttu.edu

Research Group

Pappas Receives Chancellor's Council Research Award


Pappas is an associate professor in the Department of Chemistry & Biochemistry at Texas Tech. Previously serving as a senior scientist at Johnson Space Center, Pappas has earned national and international recognition for his work using new chemical methods to study and detect illnesses such as heart disease and cancer, and has been noted as one of the top bioanalytical chemists in the nation.
Photos

Principal Research Interests


Our research focuses on bioanalytical methodologies to solve medical problems. My research group vertically integrates our efforts to solve these problems—developing new, disruptive technologies. Our work is translational in nature, as we span multiple disciplines to elucidate complex biological problems. The overall theme of our work is the integration of microfluidic and spectroscopic approaches to investigate the areas of heart disease, blood analysis, cancer, and several other biomedical issues. Our work involves collaborators in the medical community and within our own department as well.

One of the key areas of our research involves the role of oxygen and hypoxia in cell survival. We have studied hypoxia in heart disease and now focus our efforts on hypoxic tumor cells. We use a multi-culture cell chip for low-shear culture, gradient formation, and spectroscopic diagnostics. We are currently exploring the role of oxygen in cell survival mechanisms as potential therapeutic targets.
We have also pioneered several single-molecule and correlation methods for single-cell analysis. This project deals with the development of a new spectroscopic probe and single-molecule measurements in static or flowing cells for rapid assessment of protease activity. Working with Michael Mayer's group at TTU, we synthesized a new protease probe based on the Nile Blue derivative 9-di-3-sulfonyl-propyl-aminobenzo[a]phenoxazonium perchlorate (2SBPO). This new probe, combined with our single-molecule measurements, has radically changed the temporal resolution of apoptosis analysis.

Our group also has a strong presence in the cell separations community. We have published a series of papers dealing with geometric effects in fluid flow and their influence in affinity cell capture. We utilized these geometric effects to create a chip that has three-dimensional flow (a multi-inlet chip) for enhanced cell capture using negative selection. Negative cell selection approaches are often preferable in cell sorting, as no labeling of the target cell is required. We are currently developing a new class of microfluidic chips aimed at simple and reliable medical diagnostics.

Representative Publications


D. Pappas, "Microfluidics and Cancer Analysis: Cell Separation, Cell/Tissue Culture, Cell Mechanics, and Integrated Analysis Systems," The Analyst, 141, 525-535 (2016). (Special Issue: Cancer Detection and Diagnosis).
W. Li, Y. Gao, D. Pappas, "A Complementary Method to CD4 Counting: Measurement of CD4+/CD8+ T Lymphocyte Ratio in a Tandem Affinity Microfluidic System," Biomedical Microdevices, 17, 113 (2015).
M. Dong, Y. Tian, D. Pappas, "Synthesis of a Red Fluorescent, Dye- Conjugated Ag@SiO2 Nanocomposite for Cell Immunofluorescence," Applied Spectroscopy, 69, 215-221 (2015).
H. Somaweera, S. Haputhanthri, A. Ibraguimov, D. Pappas, "On-Chip Gradient Generation in 256 Microfluidic Cell Cultures: Simulation and Experimental Validation" The Analyst, 140, 5029-5038 (2015).
Y. Liu, T. Germain, D. Pappas, "Microfluidic Antibody Arrays for Simultaneous Cell Separation and Stimulus," Analytical and Bioanalytical Chemistry 406, 7867-7873 (2014).
G. Khanal, S. Hiemstra, D. Pappas, "Probing Hypoxia-Induced Staurosporine Resistance in Prostate Cancer Cells with a Microfluidic Culture System," The Analyst 139, 3274-3280 (2014).
M. Dong, Y. Tian, D. Pappas, "Facile Functionalization of Ag@SiO2 Core-Shell Metal Enhanced Fluorescence Nanoparticles for Cell Labeling," Analytical Methods  6, 1598-1602 (2014).
H. Somaweera, A. Imbramuov, D. Pappas, "Generation of a Chemical Gradient Across an Array of 256 Cell Cultures in a Single Chip," The Analyst, 138, 5566-5571 (2013).
D. Iyer, R.D. Ray, D. Pappas, "High Temporal Resolution Confocal Fluorescence Measurements for Ultrasensitive Detection of Early Stage Apoptosis," The Analyst, 138, 4892-4897 (2013).

Contact

Department of Chemistry & Biochemistry