4422 Chem. Soc. Rev., 2010, 39, 4422–4432 This journal is c The Royal Society of Chemistry 2010 Redox-active radical scavenging nanomaterials Ajay Karakoti, a Sanjay Singh, b Janet M. Dowding, b Sudipta Seal acd and William T. Self* b Received 17th December 2009 DOI: 10.1039/b919677n Reactive oxygen and nitrogen species play a critical role in many degenerative diseases and in aging. Nanomaterials, especially modified fullerenes and cerium oxide nanoparticles, have been shown to effectively protect mammalian cells against damage caused by increased reactive oxygen or nitrogen species, likely through their direct reaction with superoxide radical, since each of these materials has been shown to act as effective superoxide dismutase mimetics in vitro. This critical review discusses the chemistry of these nanomaterials and the context in which their radical scavenging activities have been studied in biological model systems. Current studies are focused on determining the uptake, metabolism, distribution, toxicity and fate of these nanomaterials in cell and animal model systems. Ultimately if shown to be safe, these nanomaterials have the potential to be used to reduce the damaging effects of radicals in biological systems (101 references). 1. Summary The expansion of materials science to the nanoscale has brought with it excitement and promise to engineer materials that can revolutionize science. Most notably, the ability to make materials at the nanoscale has the potential to allow for targeted delivery of drugs, improve catalysis for industrial processes, enhance our ability to harness light energy or even to probe the basic nature of the atom itself. One unexpected finding, that nanoparticles can act as radical scavengers, has arisen from the study of two materials, fullerenes and cerium oxide. Various forms of these nanoparticles have been engineered and studied in biological systems over the past ten years, yielding promising results to decrease damage induced by reactive oxygen and nitrogen species. 1–5 In this review, we discuss the impact of reactive oxygen and nitrogen species in biological systems, and the literature on radical scavenging properties of cerium oxide nanoparticles and modified fullerenes. In light of recent concerns about toxicity of nanomaterials in mammals, we also review the brief literature on the toxicity of these two materials. 2. The role of oxygen and nitrogen based radicals in biology and disease Since the onset of an oxygenated environment, predicted at somewhere near 2.5 billion years ago, biological organisms a Applied Materials Processing and Analysis Center, University of Central Florida, 4000 Central Florida Blvd., Engineering I, Orlando, Florida, USA b Burnett School of Biomedical Science, University of Central Florida, 4000 Central Florida Blvd., Bldg. 20 Room 124, Orlando, Florida, USA. E-mail: wself@mail.ucf.edu; Fax: +1 407-823-0956; Tel: +1 407-823-4262 c Mechanical Materials and Aerospace Engineering, University of Central Florida, 4000 Central Florida Blvd., Orlando, Florida, USA d Nanoscience Technology Center, 12424 Research Parkway Suite 400 Orlando, FL 32826, USA Ajay Karakoti Ajay S. Karakoti earned his Masters in Science (Chemistry) from University of Delhi in 2001 and obtained Masters in Technology from Indian Insti- tute of Technology, Bombay in 2003. He recently completed his PhD from University of Central Florida, USA under the guidance of Prof. Sudipta Seal. His research is focused on room temperature synthesis and development of bare and polymer coated rare earth oxide nanoparticles as thera- peutic agents and understanding the complex chemistry of rare earth oxides with free radicals. He will continue this work at Pacific Northwest National Laboratory, USA where he joined as a postdoctoral research scholar. Sanjay Singh Dr Sanjay Singh obtained his BS degree from Ewing Christian College in Allahabad and MS from University of Allahabad. He obtained his PhD from National Chemical Laboratory under the joint supervision of Dr B. L. V. Prasad, Dr Murali Sastry and Dr Asmita Prabhune in 2008. Currently, he is post- doctoral research fellow in Dr William Self’s group in University of Central Florida. His research interests include synthesis of nanomaterials, toxicity assessment and appli- cation of nanomaterials to biomedical science. CRITICAL REVIEW www.rsc.org/csr | Chemical Society Reviews Downloaded by Pennsylvania State University on 12 June 2011 Published on 17 August 2010 on http://pubs.rsc.org | doi:10.1039/B919677N View Online