| AVS 56th International Symposium & Exhibition | |
| Applied Surface Science | Wednesday Sessions |
| Session AS+NS-WeM |
| Session: | Nanoparticle and Nanoscale Surface Chemistry II |
| Presenter: | A.S. Karakoti, University of Central Florida |
| Authors: | A.S. Karakoti, University of Central Florida S. Singh, University of Central Florida A. Kumar, University of Central Florida S.V.N.T. Kuchibhatla, Environmental and Molecular Sciences Laboratory W.T. Self, University of Central Florida S. Seal, University of Central Florida |
| Correspondent: | Click to Email |
The astounding progress of nanotechnology in numerous areas of science and biotechnology is posed with a significant challenge of overcoming the nanotoxicological properties of these materials. More often than not nanomaterials produce oxidative stress when exposed to cellular environment leading to rapid cell death. While several nanomaterials are linked with oxidative stress; cerium oxide nanoparticles (CNPs) show an inverse behavior by scavenging the reactive oxygen species (ROS) thereby reducing the oxidative stress and acting as antioxidant oxides. The antioxidant properties of nanoceria originate from its redox properties, surface chemistry and nanoparticulate size. It was observed that a critical ratio of Ce3+/Ce4+ was required for exhibiting better antioxidant properties. Due to the reversible nature of its redox properties i.e. CNPs can regenerate its active radical scavenging oxidation state upon interaction with ROS such as peroxide and superoxide. To increase the biocompatibility and cell permeability characteristics, CNPs were synthesized in biocompatible mediums such as polyethylene glycol (PEG) and dextran. Cell viability studies showed excellent biocompatibility of the CNPs synthesized in biocompatible mediums. The antioxidant property of CNPs in these medium was compared to the water based CNPs using classical superoxide dismutase (SOD) model and it was found SOD mimetic activity was unaltered by the presence of organic coating on CNPs. Reaction of hydrogen peroxide with CNPs was used to compare the changes in oxidation state of CNPs upon interaction with peroxide species. While both PEG and dextran showed tunable redox property; it was found that the redox property of PEG based CNPs were acutely affected by medium due to change in the polarity and dielectric constant of the medium. A clear indication of formation of charge transfer complex was found with PEG while no such complex was observed with dextran. Additionally CNPs synthesized in PEG (5 – 80 vol% PEG) showed concentration dependent red shift in the formation of CNP-PEG charge transfer complex. Upon dialysis it was found that the polymer formed a stable coating on the surface of CNPs and the surface coating was linked to the observed differences in the regeneration of the oxidation state of nanoparticles. High resolution transmission electron microscopy, Fourier transform infra red spectroscopy and UV-visible spectroscopy were used to characterize the particle size, nature of coating and dynamic oxidation state of nanoceria. X-ray photoelectron spectroscopy used to probe the surface chemistry and oxidation state of CNPs.