News
Seminar Series
October 17, 2008 Location TBA |
Dr. Sudipta Seal Regenerative catalytic rare earth nanoparticles as therapeutics Co-Hosts: CNN and the Division of Materials Science & Engineering |
| Abstract: We have merged nanoscale engineering with cell biology to potentially intervene in a common biomedical pathology, ranging from aging to free radical-induced cell dysfunction. Using a simple wet chemical synthesis method, we have successfully created biocompatible ceria nanoparticles (NPs) with or without dopants. For the first time, we have observed that the oxidation state of cerium changes with the environment and time, subsequently affecting the variation in the absorption edge. These environmentally induced changes in the band edge are likely to contribute to inconsistencies regarding quantum confinement effects for nanoceria reported in the literature. Analysis of the UV – Vis data indicates that the use of effective mass approximation (EMA) theory to nanoceria is not always appropriate. The reaction mechanisms presented to discuss the results strengthen the hypothesis that these rare earth NPs can quench reactive oxygen species, while protecting the mammalian cells (such as, neuronal (brain) cells, spinal cord, stem cells, preventing radiation induced damage during chemotherapy, lupus disease), in particular, retinal cells are emphasized in this talk. We have further demonstrated that nanoceria protect retinal neurons from cell death caused by reactive oxygen species (ROS) generated by H2O2. Since this same ROS may contribute to light induced photoreceptor cell death and/or other types of retinal degenerations, we think that these nanoparticles can be used as potential therapeutic treatments for protection of retinal neurons and other neurodegenerative diseases. Utilizing various biochemical assays to pinpoint a molecular mechanism, ceria NPs are shown to act as catalysts that mimic superoxide dismutase (SOD) with the catalytic rate constant exceeding that determined for the enzyme SOD. Combining with detailed surface chemical studies, the results strongly suggest that the surface oxidation state of nanoceria plays an integral role in the SOD mimetic activity of nanoceria and that ability of rare earth NPs to scavenge superoxide is directly related to cerium (III) concentrations at the surface of the particle. The role of size and stability of ceria NPs with varying shape and size in preparing biocompatible and stable suspensions is discussed and supported through MD simulations. It was found that the redox kinetics of ceria NPs can be controlled with the type of medium. We hypothesize that the unique valence and oxygen defect structure of engineered NPs, promotes cell longevity and protects against free radical-mediated injury by acting as a regenerative free radical scavenger. First-Principle geometry optimizations of atomic clusters of ceria+peroxides simulating hydrogen peroxide chemisorbed on the NP (111) oxygen-terminated surface used Density Functional Theory with Gaussian basis set and Effective Core potentials to validate our experimental findings. (Nanotechnology research is funded by NSF, NSF NIRT, NER, NIH, ONR YIP, MDA, NASA, US-Russia CRDF, Lockheed Martin, Siemens Westinghouse, Pratt and Whitney, SBIR Ph I and II (DOE, DOD, MDA, NASA), Plasma Process Inc., Lucent, ASRC Corporation, State of Florida). Bio: Dr. Sudipta Seal joined the Advanced Materials Processing and Analysis Center (AMPAC) and Mechanical, Materials and Aerospace Engineering (MMAE) at the University of Central Florida in 1997. He has been consistently productive in research, instruction and service to the University of Central Florida (UCF) since1998. He has served as NanoInitiative Coordinator for the Vice-President of Research & Commercialization. |
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